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Kinetic Model under Light-Limited Condition for Photoinitiated Thiol–Ene Coupling ReactionsClick to copy article linkArticle link copied!
- Kurt W. E. Sy PieccoKurt W. E. Sy PieccoDepartment of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United StatesMore by Kurt W. E. Sy Piecco
- Ahmed M. AboelenenAhmed M. AboelenenDepartment of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United StatesMore by Ahmed M. Aboelenen
- Joseph R. PyleJoseph R. PyleDepartment of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United StatesMore by Joseph R. Pyle
- Juvinch R. VicenteJuvinch R. VicenteDepartment of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United StatesMore by Juvinch R. Vicente
- Dinesh GautamDinesh GautamDepartment of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United StatesMore by Dinesh Gautam
- Jixin Chen*Jixin Chen*E-mail: [email protected]Department of Chemistry and Biochemistry, Nanoscale and Quantum Phenomena Institute and Center for Intelligent Chemical Instrumentation, Ohio University, Athens, Ohio 45701, United StatesMore by Jixin Chen
Abstract
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Thiol–ene click chemistry has become a powerful paradigm in synthesis, materials science, and surface modification in the past decade. In the photoinitiated thiol–ene reaction, an induction period is often observed before the major change in its kinetic curve, for which a possible mechanism is proposed in this report. Briefly, light soaking generates radicals following the zeroth-order reaction kinetics. The radical is the reactant that initializes the chain reaction of thiol–ene coupling, which is a first-order reaction. Combining both and under the light-limited conditions, a surprising kinetics represented by a Gaussian-like model evolves that is different from the exponential model used to describe the first-order reaction of the final product. The experimental data are fitted well with the new model, and the reaction kinetic constants can be pulled out from the fitting.
Copyright © 2018 American Chemical Society
Introduction
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Click reactions have been one of the widely used methods for chemical synthesis because of their properties, as defined by Sharpless in 2001, which are as follows: (a) they produce high yields under mild conditions, (b) they are not affected by the presence of oxygen and water, and (c) they are compatible with a wide variety of starting materials, which selectively react only with each other (i.e., the reaction is orthogonal to other organic reactions). (1) The reaction between an alkene, or an alkyne, and a thiol is widely accepted as having the properties of a click reaction. (2) It has become a powerful tool in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymerization. (3−15) This thiol–ene click reaction can follow two different mechanisms depending on the type of initiator that is used. (8) The base-catalyzed thiol–ene (also called thiol-Michael addition) reaction is initiated by adding a nucleophile, usually phosphines. (16,17) Or the reaction is initiated by exposing the thiols to heat or UV light, which generate thiyl radicals that will react with the alkene, or alkyne (Figure 1A). (18−22)
Figure 1
Figure 1. (A) Scheme for the simplified mechanism of the photoinitiated thiol–ene coupling reaction catalyzed by the addition of a chemical photoinitiator (PI). (22) (B) Schemes of the two reactions in this report.
In a series of recent studies, the most important factor governing the overall kinetics of thiol–ene polymerization was found by Bowman and co-workers to be the ratio of the propagation rate (kP) to the chain-transfer rate (kCT). (8,16,17,20,23−29) The reaction kinetics is simplified into first-order reactions with respect to either thiol or alkene, or both, depending on the kP/kCT ratio. (24) This explains the overall exponential growth curve of the product but ignores the short induction period that is often observed before the steep portion of the growth curve, making it difficult to extract the rate constants from the curve fitting. Here, we propose an expanded mechanism to explain the induction period using the same kinetic model from the literature but taking the photoinitiator into account.
In this report, we measured the reaction kinetics of vinyltrimethoxysilane (VTMS) with thioglycolic acid (TGA) photoinitiated by 2,2-dimethoxy-2-phenylacetophenone (DMPA), and VTMS with cysteamine hydrochloride (CAH) also photoinitiated by DMPA (Figure 1B) using 1H NMR spectroscopy. The mixture was exposed to a 368–400 nm light source that is 3 cm away from the sample. Silanes were used in this study because many applications require the immobilization of a molecule tailored for a specific property via the silane group. The ability to couple a molecule to a silane through thiol–ene click reactions widens the range of molecules that can be grafted onto oxide surfaces.
Experimental Section
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All reagents were purchased from Sigma-Aldrich, and all spectra were collected using a Bruker Ascend 500 MHz NMR spectrometer under the same instrument options. Reactants TGA (or CAH), VTMS, and photoinitiator DMPA were added into an NMR tube, with solvent CDCl3 for the VTMS (0.427 M), TGA (0.857 M), and DMPA (0.03 M) mixture, and (CD3)2CO–D2O (1:4 v/v) co-solvent for the VTMS (0.058 M), CAH (0.112 M), and DMPA (0.012 M) mixture to dissolve both the CAH salt and the nonpolar aromatic DMPA. Both solutions were split into two equal portions. One portion was exposed to a 368–400 nm light source with a visible light-blocking filter (Sunlite SL20 lamp, 20 W). The lamp was placed ∼3 cm away from the sample, where the power density was ∼4 mW/cm2 measured using a Thor Labs PM100-S121C photodiode sensor. UV exposure was done at specific time intervals under room temperature prior to 1H NMR measurements. The remaining portions of both solutions were left unexposed and kept as the experimental controls. Baseline correction of all 1H NMR spectra, peak area calculations, and curve fitting (using least-squares regression analysis) were performed using MATLAB.
Results and Discussion
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The 1H NMR spectra in Figure 2 confirm the formation of the click reaction products from the thiol–ene coupling of the VTMS with TGA (Figure 2A), or with CAH (Figure 2B). The coupling reaction in the mixture of VTMS, TGA, and DMPA was complete in less than 5 min of exposure to UV light (Figure 2A). The NMR spectra before and after UV exposure in Figure 2A clearly show the disappearance of the vinyl peaks in VTMS (at 5.8, 5.9, and 6.1 ppm) and the appearance of new peaks at 1.0 and 2.7 ppm that indicate the presence of the thioether product. (30) The intensity of the TGA thiol peak at around 2.0 ppm was also reduced to half, which is consistent with the initial thiol–vinyl concentration ratio of 2:1 and a 1:1 thiol–vinyl reaction stoichiometry. These initial ratios have been reported to produce the highest yield in the shortest time. (9) The peaks around 3.6 ppm in Figure 2A come from the hydrolysis of the Si–OCH3 groups. Control experiments showed that indoor room lighting has no effect and that UV light is necessary for initiating the thiol–ene reaction. Without UV exposure, the NMR spectra in the control experiment (Figure 2C) indicate that no reaction occurs after 1 h of incubation at room temperature and under room light.
Figure 2
Figure 2. (A) 1H NMR spectra of the reactant mixture of VTMS, TGA, and DMPA in CDCl3, before (red trace) and after (blue trace) exposure to the solar simulator for 300 s. (B) 1H NMR spectra of the reactant mixture of VTMS, CAH, and DMPA in (CD3)2CO–D2O (1:4 v/v) co-solvent, before (red trace) and after (blue trace) exposure to the solar simulator for 150 s. (C, D) 1H NMR spectra of control experiments of the unexposed reaction mixtures of (C) VTMS with TGA showing no change in the vinyl and thiol peaks, and (D) VTMS with CAH also showing no change in the vinyl peak without UV light exposure.
The absence of VTMS-homopolymerization products is consistent with the click property of the thiol–ene coupling reported in the literature, (8) whose products would have shown NMR peaks between 0.5 and 0.9 ppm for the methyl protons in the −Si–CH2– group, (31−33) which were negligible in the 1H NMR spectra that were collected.
The 1H NMR spectra of the mixture of VTMS, CAH, and DMPA before and after exposure to UV light are shown in Figure 2B. The hydrogen peak of HOD at ∼4.4 ppm is broadened due to its hydrogen bonding to the other molecules; peaks from the −SH and NH3+ exchanges with D2O and are not observed; hydrogen in Si–OCH3 is observed at 3.2 ppm; hydrogens in N–CH2–CH2 are observed around 3.8 and 3.4 ppm, respectively. (34) The progress of the reaction can be most clearly tracked through the disappearance of the signal from the vinyl group at 5.9 ppm and the appearance of the thioether-specific peaks at 2.7 and 0.9 ppm. (30) The reason for seeing only one peak near the center of the chemical shifts for the vinyl group is due to the peak broadening caused by self-aggregation. (35) The methoxy groups of VTMS are partially hydrolyzed in D2O and the silanes are cross-linked, which may cause the peaks between 3.2 and 3 ppm. The reaction between VTMS and CAH was complete after 150 s of UV exposure (Figure 2B), with the thioether as the only product. The spectra from the control experiment without UV light is shown in Figure 2D, again confirming that UV light is required as indicated by the absence of the thioether product peaks (2.7 and 0.9 ppm) and the retention of the vinyl peak (5.9 ppm).
The kinetics of both reactions were monitored with a series of 1H NMR spectra collected after every exposure interval (Figure 3), with the decay curves shown in Figure 4. In the VTMS–TGA coupling (Figure 4A), the vinyl (red traces) peak gradually disappears, while the thiol (black traces) peak was gradually reduced to roughly half after exposure to UV light over time. At the same time, there was a gradual increase in the peak intensities centered at 2.73 ppm (green traces) and 0.98 ppm (blue traces), both specific to the thioether product. Figure 4B shows a plot of the integrated peak areas corresponding to each moiety in Figure 4A as a function of exposure time. The data indicate that the photoinitiated reaction between VTMS and TGA has a short induction time followed by an exponential decay of the reactants, with a corresponding exponential growth of the thioether product. The yield for TGA and VTMS is >90%. The yield for CAH and VTMS is ∼50%. The relatively lower yield of the VTMS and CAH reaction is due to the recently observed inhibition of thiol–ene reactions by amine groups. (36) Induction times were also observed in other photocatalytic reactions. (19,28,29,37) The length of the induction time is dependent on the reaction conditions, such as light intensity. (25,38)
Figure 3
Figure 3. (A) Reaction kinetics in bulk solution containing VTMS, TGA, and DMPA in CDCl3 measured by 1H NMR. The sample was exposed to 368–400 nm light for specific time intervals (0, 9, 14, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 120, 180, and 300 s) prior to each 1H NMR measurement. (B) Similar experiments performed on a reaction mixture containing VTMS, CAH, and DMPA in (CD3)2CO–D2O co-solvent (1:4 v/v) and at time intervals of 0, 5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 90, and 150 s.
Figure 4
Figure 4. (A) Selected NMR spectra of the reaction mixture of TGA, VTMS, and DMPA in CDCl3 focusing on the vinyl (red), thiol (black), and product (green and blue) regions from Figure 3. (B) Plots of integrated peak areas of the color-coded regions shown in (A). The scatter plots are integrated peak areas after each exposure time for each of the corresponding peaks in (A), which are fitted with the models described in the text. (C) Selected NMR spectra of the reaction mixture of CAH, VTMS, and DMPA in (CD3)2CO–D2O (1:4 v/v) co-solvent focusing on the vinyl (red) and product (green and blue) regions. (D) Plots of integrated peak areas of the color-coded regions shown in (C), where the scatter plots and solid traces represent integrated peak areas and fitted curves, respectively. These curves were fitted using eqs 11–13.
The kinetics of the photoinitiated thiol–ene reactions is best described by a half-Gaussian function, as shown by the solid curves in Figure 4B,D. The photocatalytic reaction cycle shown in Figure 1 has been assumed to have two competing steps in the literature, chain transfer and chain propagation. (8,27) The relative rate constants of these processes and the chain initialization and termination processes will determine the kinetic trajectory of the reaction. These processes can be specified to have the following elementary reactions expanded from the model in the literature (27)
where PI is the photoinitiator that has not been considered in the literature model; (24,27) R is an unknown molecule (e.g., another PI, oxygen, or other molecules); S, V, and SV are the thiol, vinyl, and thioether products, respectively; and “•” indicates if the species is a radical. These reactions can be grouped into three major processes. Reactions 1 and 2 are the initiation steps of the photochemical reaction. Reactions 3 and 4 are the chain-transfer and chain-propagation steps, respectively. Reactions 5–7 are the termination steps of the photoinitiated thiol–ene reaction. Varying the rates of reactions 3–7 has resulted in various exponential curves with no obvious induction period. (24) Thus, we assume the photoactivation steps to be the rate-limiting steps to check if they contribute to the induction period. This assumption is reasonable because of the low light intensity used in this study (4 mW/cm2, ∼4% sunlight intensity at air mass 1.5).
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Solving these reactions is difficult for us, but useful equations can be drawn with approximations. The reaction rate can be expressed as a function of exposure time, t, and reactant concentrations, from step 4, which produces the thioether product
We can assume that the concentration of the activated [SV•] is small and rate-limited by the light exposure because the concentration of the photoinitiator [PI] is much smaller than the concentration of vinyl [V] and thiol [S] and because the light source is relatively weak, thus making [PI•] and [R•] small. Assuming typical light-limited photoreactions as zeroth-order reactions and assuming a relatively small termination rate compared to the chain-transfer rate, (27) the concentration of the photoactivated [SV•] radical at any time, t, can be approximated as
where k8 is a new constant, which under light-limited conditions is directly proportional to k1, e.g., k8 = k1, when the radical propagation rate is much higher than the termination rate. By combining eqs 8 and 9, we get
where k9 = k4 × k8 is another new constant, [S]0 is the initial concentration of the thiol, which is consumed to form the equal amount of [SV]t. After integration with the boundary condition that at time = 0, [SV]0 = 0, we get
These three Gaussian equations are different from the exponential decay functions used in the literature, (24) but explain our light-limited induction period better (Figure 4B,D, fitted curves). A short induction period has been commonly observed in the literature for thiol–ene and thiol–yne couplings. (22,27,39) This bulk kinetic analysis allowed us to estimate the value of k9 under our experimental conditions (Table 1) and thus select a relatively longer exposure time than the half-life, t1/2, for the surface-grafting experiments, where from eq 12
We note that at a higher light intensity, the photoactivated photoinitiator reaches a steady state quickly (when eq 9 becomes [SV•] = k8), and the kinetic equations (eqs 11 and 12) converge into the single-exponential decay functions found in the literature. (22,27,39) The treatment of the rate-limiting step is different in this report compared to that in the literature, which allows us to predict the induction period observed under our reaction conditions.
(8)
(9)
(10)
(11)
(12)
(13)
(14)
| reaction | k9 (s–2) | t1/2 (s) |
|---|---|---|
| VTMS + TGA | 0.0011 | 36 |
| VTMS + CAH | 0.0014 | 31 |
In summary, we have extended the existing kinetic model and demonstrated proof-of-concept experimental evaluations to provide a more complete reaction mechanism for thiol–ene click reactions. The observed consumption rates of the reactants and formation rates of products were best fit by half-Gaussian functions (eqs 11–13) that contain induction periods. These functions look empirical but are supported by the proposed light-limited reaction mechanism. When the photoinitiating step of the chain-reaction model is the rate-limiting step, a short induction period emerges prior to the exponential-like growth of the product (or decay of the reactant) concentration. This mechanism may help the researchers to elucidate and understand the factors that underlie the confusing kinetic curves observed before.
Author Information
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- Jixin Chen - Department of Chemistry and Biochemistry, Nanoscale and Quantum Phenomena Institute and Center for Intelligent Chemical Instrumentation, , and , Ohio University, Athens, Ohio 45701, United States;
http://orcid.org/0000-0001-7381-0918;
- Ahmed M. Aboelenen - Department of Chemistry and Biochemistry, , and , Ohio University, Athens, Ohio 45701, United States;http://orcid.org/0000-0002-7880-0660
Acknowledgments
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The authors acknowledge the Ohio University startup fund, the National Science Foundation MRI program CHE-1338000, and the National Human Genome Research Institute of the National Institutes of Health Award Number R15HG009972, Prof. Michael Jensen, Prof. Katherine Cimatu Group, Prof. Hugh Richardson group, and Prof. Andrew Tangonan, for instrumental supports and beneficial discussions.
References
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This article references 39 other publications.
- 1Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click chemistry: diverse chemical function from a few good reactions. Angew. Chem., Int. Ed. 2001, 40, 2004– 2021, DOI: 10.1002/1521-3773(20010601)40:113.0.CO;2-5Google Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXksVOis78%253D&md5=61c28b416c42c87821bc8a5bc2fdec36Click chemistry: diverse chemical function from a few good reactionsKolb, Hartmuth C.; Finn, M. G.; Sharpless, K. BarryAngewandte Chemie, International Edition (2001), 40 (11), 2004-2021CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)Review with > 88 refs. Examn. of nature's favorite mols. reveals a striking preference for making carbon-heteroatom bonds over carbon-carbon bonds - surely no surprise given that carbon dioxide is nature's starting material and that most reactions are performed in water. Nucleic acids, proteins, and polysaccharides are condensation polymers of small subunits stitched together by carbon-heteroatom bonds. Even the 35 or so building blocks from which these crucial mols. are made each contain, at most, six contiguous C-C bonds, except for the three arom. amino acids. Taking a cue from nature's approach, the development of a set of powerful, highly reliable, and selective reactions for the rapid synthesis of useful new compds. and combinatorial libraries through heteroatom links (C-X-C), an approach called "click chem." is addressed. Click chem. is at once defined, enabled, and constrained by a handful of nearly perfect "spring-loaded" reactions. The stringent criteria for a process to earn click chem. status are described along with examples of the mol. frameworks that are easily made using this spartan, but powerful, synthetic strategy.
- 2Hoyle, C. E.; Lowe, A. B.; Bowman, C. N. Thiol-click chemistry: a multifaceted toolbox for small molecule and polymer synthesis. Chem. Soc. Rev. 2010, 39, 1355– 1387, DOI: 10.1039/b901979kGoogle Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjs1Ggu74%253D&md5=b5ea504263dbe971aa2017061552c15bThiol-click chemistry: a multifaceted toolbox for small molecule and polymer synthesisHoyle, Charles E.; Lowe, Andrew B.; Bowman, Christopher N.Chemical Society Reviews (2010), 39 (4), 1355-1387CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The merits of thiol-click chem. and its potential for making new forays into chem. synthesis and materials applications are described. Since thiols react to high yields under benign conditions with a vast range of chem. species, their utility extends to a large no. of applications in the chem., biol., phys., materials and engineering fields. This crit. review provides insight into emerging venues for application as well as new mechanistic understanding of this exceptional chem. in its many forms (81 refs.).
- 3Melnik, E.; Muellner, P.; Bethge, O.; Bertagnolli, E.; Hainberger, R.; Laemmerhofer, M. Streptavidin binding as a model to characterize thiol–ene chemistry-based polyamine surfaces for reversible photonic protein biosensing. Chem. Commun. 2014, 50, 2424– 2427, DOI: 10.1039/c3cc48640kGoogle ScholarThere is no corresponding record for this reference.
- 4Melnik, E. V. A.; Bruck, R.; Hainberger, R.; Lämmerhofer, M. Multi-step surface functionalization of polyimide based evanescent wave photonic biosensors and application for dna hybridization by Mach-Zehnder interferometer. Anal. Chim. Acta 2011, 699, 206– 215, DOI: 10.1016/j.aca.2011.05.017Google ScholarThere is no corresponding record for this reference.
- 5Skinner, E. K.; Whiffin, F. M.; Price, G. J. Room temperature sonochemical initiation of thiol-ene reactions. Chem. Commun. 2012, 48, 6800– 6802, DOI: 10.1039/c2cc32457aGoogle Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XotleksL8%253D&md5=67cbb749ef68498eb2828ea847536d3bRoom temperature sonochemical initiation of thiol-ene reactionsSkinner, Emily K.; Whiffin, Fraeya M.; Price, Gareth J.Chemical Communications (Cambridge, United Kingdom) (2012), 48 (54), 6800-6802CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)Thiol-ene 'click' reactions have been initiated for a range of primary alkenes using ultrasound in both toluene and water. The method is particularly effective in aq. solns. in the presence of air.
- 6Taghavikish, M.; Subianto, S.; Dutta, N.; Roy Choudhury, N. Novel thiol-ene hybrid coating for metal protection. Coatings 2016, 6, 17, DOI: 10.3390/coatings6020017Google ScholarThere is no corresponding record for this reference.
- 7Kade, M. J.; Burke, D. J.; Hawker, C. J. The power of thiol-ene chemistry. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 743– 750, DOI: 10.1002/pola.23824Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXntlahug%253D%253D&md5=100eb92de04ae4f4a8b5e26bc20b4fbfThe power of thiol-ene chemistryKade, Matthew J.; Burke, Daniel J.; Hawker, Craig J.Journal of Polymer Science, Part A: Polymer Chemistry (2010), 48 (4), 743-750CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)A review. As a tribute to Professor Charlie Hoyle, we take the opportunity to review the impact of thiol-ene chem. on polymer and materials science over the past 5 years. During this time, a renaissance in thiol-ene chem. has occurred with recent progress demonstrating its unique advantages when compared with traditional coupling and functionalization strategies. Addnl., the robust nature of thiol-ene chem. allows for the prepn. of well-defined materials with few structural limitations and synthetic requirements. To illustrate these features, the utility of thiol-ene reactions for network formation, polymer functionalization, dendrimer synthesis, and the decoration of three-dimensional objects is discussed. Also, the development of the closely related thiol-yne chem. is described. 2010 Wiley Periodicals, Inc., J Polym Sci Part A: Polym Chem 48: 743-750, 2010.
- 8Hoyle, C. E.; Bowman, C. N. Thiol-ene click chemistry. Angew. Chem., Int. Ed. 2010, 49, 1540– 1573, DOI: 10.1002/anie.200903924Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXisVaktr8%253D&md5=0c104f1f1df66670742b1430ac01d1daThiol-Ene Click ChemistryHoyle, Charles E.; Bowman, Christopher N.Angewandte Chemie, International Edition (2010), 49 (9), 1540-1573CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Following Sharpless' visionary characterization of several idealized reactions as click reactions, the materials science and synthetic chem. communities have pursued numerous routes toward the identification and implementation of these click reactions. Herein, the authors review the radical-mediated thiol-ene reaction as one such click reaction. This reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Further, the thiol-ene reaction is most frequently photoinitiated, particularly for photopolymns. resulting in highly uniform polymer networks, promoting unique capabilities related to spatial and temporal control of the click reaction. The reaction mechanism and its implementation in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymn. are all reviewed.
- 9Lowe, A. B. Thiol-ene “ click ” reactions and recent applications in polymer and materials synthesis: a first update. Polym. Chem. 2014, 5, 4820– 4870, DOI: 10.1039/C4PY00339JGoogle Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1ektrnN&md5=0ee49a0e502b2e82e5cec0b9b4c9e408Thiol-ene "click" reactions and recent applications in polymer and materials synthesis: a first updateLowe, Andrew B.Polymer Chemistry (2014), 5 (17), 4820-4870CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)A review. This contribution serves as an update to a previous review (Polym. Chem. 2010, 1, 17-36) and highlights recent applications of thiol-ene 'click' chem. as an efficient tool for both polymer/materials synthesis as well as modification. This current contribution covers examples from the literature published up to ca. mid 2013. It is not intended to be exhaustive but rather serves to highlight many of the new and exciting applications where researchers have applied thiol-ene chem. in advanced macromol. engineering and materials chem.
- 10Grim, J. C.; Marozas, I. A.; Anseth, K. S. Thiol-ene and photo-cleavage chemistry for controlled presentation of biomolecules in hydrogels. J. Controlled Release 2015, 219, 95– 106, DOI: 10.1016/j.jconrel.2015.08.040Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVWgu73I&md5=a49d2f3c6406686e5998f453a3b2f1c9Thiol-ene and photo-cleavage chemistry for controlled presentation of biomolecules in hydrogelsGrim, Joseph C.; Marozas, Ian A.; Anseth, Kristi S.Journal of Controlled Release (2015), 219 (), 95-106CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)Hydrogels have emerged as promising scaffolds in regenerative medicine for the delivery of biomols. to promote healing. However, increasing evidence suggests that the context that biomols. are presented to cells (e.g., as sol. verses tethered signals) can influence their bioactivity. A common approach to deliver biomols. in hydrogels involves phys. entrapping them within the network, such that they diffuse out over time to the surrounding tissues. While simple and versatile, the release profiles in such system are highly dependent on the mol. wt. of the entrapped mol. relative to the network structure, and it can be difficult to control the release of two different signals at independent rates. In some cases, supraphysiol. high loadings are used to achieve therapeutic local concns., but uncontrolled release can then cause deleterious off-target side effects. In vivo, many growth factors and cytokines are stored in the extracellular matrix (ECM) and released on demand as needed during development, growth, and wound healing. Thus, emerging strategies in biomaterial chem. have focused on ways to tether or sequester biol. signals and engineer these bioactive scaffolds to signal to delivered cells or endogenous cells. While many strategies exist to achieve tethering of peptides, protein, and small mols., this review focuses on photochem. methods, and their usefulness as a mild reaction that proceeds with fast kinetics in aq. solns. and at physiol. conditions. Photo-click and photo-caging methods are particularly useful because one can direct light to specific regions of the hydrogel to achieve spatial patterning. Recent methods have even demonstrated reversible introduction of biomols. to mimic the dynamic changes of native ECM, enabling researchers to explore how the spatial and dynamic context of biomol. signals influences important cell functions. This review will highlight how two photochem. methods have led to important advances in the tissue regeneration community, namely the thiol-ene photo-click reaction for bioconjugation and photocleavage reactions that allow for the removal of protecting groups. Specific examples will be highlighted where these methodologies have been used to engineer hydrogels that control and direct cell function with the aim of inspiring their use in regenerative medicine.
- 11McKenas, C. G.; Fehr, J. M.; Donley, C. L.; Lockett, M. R. Thiol-ene modified amorphous carbon substrates: surface patterning and chemically modified electrode preparation. Langmuir 2016, 32, 10529– 10536, DOI: 10.1021/acs.langmuir.6b02961Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFGrsrrF&md5=73a4ddf4392855ec6c2803f20b3a8ca9Thiol-Ene Modified Amorphous Carbon Substrates: Surface Patterning and Chemically Modified Electrode PreparationMcKenas, Catherine G.; Fehr, Julia M.; Donley, Carrie L.; Lockett, Matthew R.Langmuir (2016), 32 (41), 10529-10536CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)There are a no. of wet chem. methods capable of tailoring the reactivity and wettability of amorphous carbon (aC) films, but few of these chemistries are compatible with photopatterning. The authors introduce a method to install thiol groups directly onto the surface of aC films. These terminal thiols are compatible with thiol-ene click reactions, which allowed us to rapidly functionalize and pattern the surface of the aC films. The aC films were characterized and it was confirmed that the installation of surface-bound thiols did not significantly oxidize the surface or change its topog. The authors detd. the conditions needed to selectively attach alkene-contg. mols. to these films and show the reaction is proceeding through a thiol-mediated reaction. The utility of this approach was demonstrated by photopatterning the aC films and prepg. ferrocene-modified aC electrodes.
- 12Wendeln, C.; Rinnen, S.; Schulz, C.; Arlinghaus, H. F.; Ravoo, B. J. Photochemical microcontact printing by thiol-ene and thiol-yne click chemistry. Langmuir 2010, 26, 15966– 15971, DOI: 10.1021/la102966jGoogle Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtFygt7vE&md5=b68f5e961c2078f219f644e5aa628fc0Photochemical Microcontact Printing by Thiol-Ene and Thiol-Yne Click ChemistryWendeln, Christian; Rinnen, Stefan; Schulz, Christian; Arlinghaus, Heinrich F.; Ravoo, Bart JanLangmuir (2010), 26 (20), 15966-15971CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)This article describes the microstructured immobilization of functional thiols on alkene- and alkyne-terminated self-assembled monolayers on silicon oxide substrates by photochem. microcontact printing. A photochem. thiol-ene or thiol-yne "click" reaction was locally induced in the area of contact between stamp and substrate by irradn. with UV light (365 nm). The immobilization reaction by photochem. microcontact printing was verified by contact angle measurements, XPS, at. force microscopy, and time-of-flight secondary ion mass spectrometry. The reaction rate of photochem. microcontact printing by thiol-ene chem. was studied using time dependent contact angle measurements. The selective binding of lectins to galactoside microarrays prepd. by photochem. microcontact printing was also demonstrated. It was found that photochem. microcontact printing results in a high surface coverage of functional thiols within 30 s of printing even for dil. (mM) ink solns.
- 13Wu, J.-T.; Huang, C.; Liang, W.; Wu, Y.; Yu, J.; Chen, H. Reactive polymer coatings: a general route to thiol-ene and thiol-yne click reactions. Macromol. Rapid Commun. 2012, 33, 922– 927, DOI: 10.1002/marc.201200011Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XisFajtrY%253D&md5=f8b2124c4427f0faba085f53083fb931Reactive Polymer Coatings: A General Route to Thiol-ene and Thiol-yne Click ReactionsWu, Jyun-Ting; Huang, Chi-Hui; Liang, Wei-Chieh; Wu, Yen-Lin; Yu, Jiashing; Chen, Hsien-YehMacromolecular Rapid Communications (2012), 33 (10), 922-927CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)Reactive polymer coatings were synthesized via chem. vapor deposition (CVD) polymn. process. These coatings decouple surface design from bulk properties of underlying materials and provide a facile and general route to support thiol-ene and thiol-yne reactions on a variety of substrate materials. Through the reported technique, surface functions can be activated through a simple design of thiol-terminated mols. such as polyethylene glycols (PEGs) or peptides (GRGDYC), and the according biol. functions were demonstrated in controlled and low-fouling protein adsorptions as well as accurately manipulated cell attachments.
- 14Cole, M. A.; Bowman, C. N. Evaluation of thiol-ene click chemistry in functionalized polysiloxanes. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 1749– 1757, DOI: 10.1002/pola.26551Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhsVaqtrs%253D&md5=214614fa6376267e17d54a82c2c39a51Evaluation of thiol-ene click chemistry in functionalized polysiloxanesCole, Megan A.; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2013), 51 (8), 1749-1757CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)Polysiloxanes are commonly used in a myriad of applications, and the "click" nature of the thiol-ene reaction is well suited for introducing alternative functionalities or for crosslinking these ubiquitous polymers. As such, understanding of the thiol-ene reaction in the presence of silicones is valuable and would lead to enhanced methodologies for modification and crosslinking. Here, the thiol-ene reaction kinetics were investigated in functionalized oligosiloxanes having varying degrees of thiol functionalization (SH), π-π interactions (from diphenyls, DP), and ene types (C=C). In the ene-functionalized oligomers, π-π interactions were controlled through the use of dioctyl repeats (DO). The polymn. rate and rate-limiting steps were detd. for all systems contg. an allyl-functionalized oligomer, and rates ranging from 0.10 to 0.54 mol L-1 min-1 were seen. The rate-limiting step varied with the oligomer compn.; examples of rate-limited propagation (5:3:2 C=C:DP:DO/1:1 SH:DP) or chain transfer (5:3:2 C=C:DP:DO/3:1 SH:DP) were found in addn. to cases with similar reaction rate consts. (5:2:3 C=C:DP:DO/1:1 SH:DP). None of the siloxanes were found to exhibit autoacceleration despite their relatively high viscosities. Instead, the allyl-, vinyl-, and acrylate-functionalized siloxanes were all found to undergo unimol. termination based on their high α scaling values (0.98, 0.95, and 0.82, resp.) in the relation Rp .varies. Riα. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013.
- 15Li, Z.; Zhu, Z.; Chueh, C.-C.; Luo, J.; Jen, A. K.-Y. Facile thiol-ene thermal crosslinking reaction facilitated hole-transporting layer for highly efficient and stable perovskite solar cells. Adv. Energy Mater. 2016, 6, 1601165 DOI: 10.1002/aenm.201601165Google ScholarThere is no corresponding record for this reference.
- 16Chan, J. W.; Hoyle, C. E.; Lowe, A. B.; Bowman, M. Nucleophile-initiated thiol-Michael reactions: effect of organocatalyst, thiol, and ene. Macromolecules 2010, 43, 6381– 6388, DOI: 10.1021/ma101069cGoogle Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXoslehsrk%253D&md5=95aca849447e21d8549b47a07994490eNucleophile-Initiated Thiol-Michael Reactions: Effect of Organocatalyst, Thiol, and EneChan, Justin W.; Hoyle, Charles E.; Lowe, Andrew B.; Bowman, MarkMacromolecules (Washington, DC, United States) (2010), 43 (15), 6381-6388CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A detailed evaluation of the kinetics of the thiol-Michael reaction between hexanethiol and hexyl acrylate is described. It is shown that primary amines are more effective catalysts than either secondary or tertiary amines with, for example, quant. conversion being achieved within 500 s in the case of hexylamine with an apparent rate const. of 53.4 mol L-1 s-1 at a catalyst loading of 0.057 mol %. Certain tertiary phosphines, and esp. tri-n-propylphosphine and dimethylphenylphosphine, are shown to be even more effective species even at concns. 2 orders of magnitude lower than employed for hexylamine and performed in soln. with quant. conversions reached within ca. 100 s for both species and apparent rate consts. of 1810 and 431 mol L-1 s-1, resp. The nature of the thiol is also demonstrated to be an important consideration with mercaptoglycolate and mercaptopropionate esters being significantly more reactive than hexanethiol with reactivity mirroring the pKa of the thiols. Likewise, it is shown that the structure of the activated ene is also crucial with the degree of activation and ene-substitution pattern being important features in detg. reactivity. In terms of reaction with hexanethiol in the presence of hexylamine as catalyst, it is shown that propylmaleimide > di-Et fumarate > di-Et maleate > dimethylacrylamide > acrylonitrile > Et crotonate > Et cinnamate > Et methacrylate.
- 17Nair, D. P.; Podgórski, M.; Chatani, S.; Gong, T.; Xi, W.; Fenoli, C. R.; Bowman, C. N. The thiol-michael addition click reaction: a powerful and widely used tool in materials chemistry. Chem. Mater. 2014, 26, 724– 744, DOI: 10.1021/cm402180tGoogle Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXht12ht7vK&md5=d48828084a19cdfc3634693ca9feed6fThe thiol-Michael addition click reaction. A powerful and widely used tool in materials chemistryNair, Devatha P.; Podgorski, Maciej; Chatani, Shunsuke; Gong, Tao; Xi, Weixian; Fenoli, Christopher R.; Bowman, Christopher N.Chemistry of Materials (2014), 26 (1), 724-744CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)A review. The key attribute of the thiol-Michael addn. reaction that makes it a prized tool in materials science is its modular click nature, which allows for the implementation of this highly efficient, green reaction in applications that vary from small mol. synthesis to in situ polymer modifications in biol. systems to the surface functionalization of material coatings. Over the past few decades, interest in the thiol-Michael addn. reaction increased dramatically, as is evidenced by the no. of studies that were dedicated to elucidating different aspects of the reaction that range from an in-depth anal. aimed at understanding the mechanistic pathways of the reaction to synthetic studies that have examd. modifying mol. structures with the aim of yielding highly efficient thiol-Michael reaction monomers. This review examd. the reaction mechanisms, the substrates and catalysts used in the reaction, and the subsequent implementation of the thiol-Michael reaction in materials science over the years, with particular emphasis on the recent developments in the arena over the past decade.
- 18Hoyle, C. E.; Lee, T. Y.; Roper, T. Thiol-enes: chemistry of the past with promise for the future. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 5301– 5338, DOI: 10.1002/pola.20366Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXptVKgsrs%253D&md5=1dddaa64f77f7f79c3f9e49333cf693cThiol-enes: Chemistry of the past with promise for the futureHoyle, Charles E.; Lee, Tai Yeon; Roper, ToddJournal of Polymer Science, Part A: Polymer Chemistry (2004), 42 (21), 5301-5338CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)A review. The photopolymn. of mixts. of multifunctional thiols and enes is an efficient method for the rapid prodn. of films and thermoset plastics with unprecedented phys. and mech. properties. One of the major obstacles in traditional free-radical photopolymn. is essentially eliminated in thiol-ene polymns. because the polymn. occurs in air almost as rapidly as in an inert atm. Virtually any type of ene will participate in a free-radical polymn. process with a multifunctional thiol. Hence, it is possible to tailor materials with virtually any combination of properties required for a particular application.
- 19Derboven, P.; D’hooge, D. R.; Stamenovic, M. M.; Espeel, P.; Marin, G. B.; Du Prez, F. E.; Reyniers, M.-F. Kinetic modeling of radical thiol–ene chemistry for macromolecular design: importance of side reactions and diffusional limitations. Macromolecules 2013, 46, 1732– 1742, DOI: 10.1021/ma302619kGoogle Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXivVyhtrY%253D&md5=7d7dd04bb4828f46263e8551a5dfe30bKinetic Modeling of Radical Thiol-Ene Chemistry for Macromolecular Design: Importance of Side Reactions and Diffusional LimitationsDerboven, Pieter; D'hooge, Dagmar R.; Stamenovic, Milan M.; Espeel, Pieter; Marin, Guy B.; Du Prez, Filip E.; Reyniers, Marie-FrancoiseMacromolecules (Washington, DC, United States) (2013), 46 (5), 1732-1742CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)The radical thiol-ene coupling of thiol-functionalized polystyrene (PS-SH) with dodecyl vinyl ether (DVE) and the polystyrene-b-poly(vinyl acetate) (PS-b-PVAc) polymer-polymer conjugation using 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator are modeled to assess the importance of diffusional limitations and side reactions. Intrinsic chem. rate coeffs. are detd. based on a kinetic study of the coupling of benzyl thiol (BT) and DVE. The addn. and transfer reactions are chem. controlled, whereas diffusional limitations on termination slightly increase the coupling efficiency. Termination by recombination of carbon-centered radicals and addn. of DMPA derived radicals to DVE are shown to be mainly responsible for the reduced coupling efficiency in case polymeric species are involved. The obtained results confirm the idea to disregard radical thiol-ene chem. as a true member of the family of "click" chem. techniques for polymer-polymer conjugation and show that the initial conditions have a significant impact on the coupling efficiency.
- 20Okay, O.; Bowman, C. N. Kinetic modeling of thiol-ene reactions with both step and chain growth aspects. Macromol. Theory Simul. 2005, 14, 267– 277, DOI: 10.1002/mats.200500002Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXkslyktLk%253D&md5=ca6031bbf325aa31849c6c2311e621a4Kinetic modeling of thiol-ene reactions with both step and chain growth aspectsOkay, Oguz; Bowman, Christopher N.Macromolecular Theory and Simulations (2005), 14 (4), 267-277CODEN: MTHSEK; ISSN:1022-1344. (Wiley-VCH Verlag GmbH & Co. KGaA)A kinetic model is presented for thiol-ene crosslinking photopolymns. including the allowance for chain growth reaction of the ene, i.e., homopolymn. The kinetic model is based on a description of the av. chain lengths derived from differential equations of the type of Smoluchowski coagulation equations. The method of moments was applied to obtain av. properties of thiolene reaction systems. The model predicts the mol. wt. distribution of active and inactive species in the pregel regime of thiol-enes, as well as the gel points depending on the synthesis parameters. It is shown that, when no homopolymn. is allowed, the av. mol. wts. and the gel point conversion are given by the typical equations valid for the step-growth polymn. Increasing the extent of homopolymn. also increases the av. mol. wts. and shifts the gel point toward lower conversions and shorter reaction times. It is also shown that the ratio of thiyl radical propagation to the chain transfer kinetic parameter (Kp1/Ktr) affects the gelation time, tcr. Gelation occurs earlier as the Kp1/Ktr ratio is increased due to the predominant attack of thiyl radicals on the vinyl groups and formation of more stable carbon radicals. The gel point in thiol-ene reactions is also found to be very sensitive to the extent of cyclization, particularly, if the monomer functionalities are low.
- 21Bordoni, A. V.; Lombardo, M. V.; Wolosiuk, A. Photochemical radical thiol–ene click-based methodologies for silica and transition metal oxides materials chemical modification: a mini-review. RSC Adv. 2016, 6, 77410– 77426, DOI: 10.1039/C6RA10388JGoogle Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1OkurbM&md5=df0afa33ac5ca783ac47ef78a9d7c3aaPhotochemical radical thiol-ene click-based methodologies for silica and transition metal oxides materials chemical modification: a mini-reviewBordoni, Andrea V.; Lombardo, M. Veronica; Wolosiuk, AlejandroRSC Advances (2016), 6 (81), 77410-77426CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)Although known for more than 40 years in the polymer chem. field, the photochem. radical thiol-ene addn. (PRTEA) has been recently recognized as a chem. reaction with click characteristics. Photoinitiation enables spatial and temporal control of this highly efficient reaction, bridging simple org. chem. with high-end materials synthesis and surfaces functionalization. In this minireview, we focus on the latest contributions based on the PRTEA for the synthesis of chem. precursors for silica and transition metal oxides (TMO) based materials. We summarize the mechanism of the PRTEA, the development of new families of photoinitiators and how this extremely simple approach has spilled over into the materials science arena with clear success. In particular, PRTEA adds to the collective efforts for building a reliable and straightforward chem. toolbox for surface modification and the prodn. of sol-gel precursors, nanoparticles and thin films. The excellent perspectives for simple mol. and supramol. building block synthesis opens up a rational synthetic route for the design and integration of these components in multipurpose platforms.
- 22Fairbanks, B. D.; Love, D. M.; Bowman, C. N. Efficient polymer-polymer conjugation via thiol-ene click reaction. Macromol. Chem. Phys. 2017, 218, 1700073 DOI: 10.1002/macp.201700073Google ScholarThere is no corresponding record for this reference.
- 23Reddy, S. K.; Cramer, N. B.; Bowman, C. N. Thiol-vinyl mechanisms. 1. termination and propagation kinetics in thiol-ene photopolymerizations. Macromolecules 2006, 39, 3673– 3680, DOI: 10.1021/ma060008eGoogle Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XjtlartLc%253D&md5=0f319d58709c6af5f8832dd5baf33320Thiol-Vinyl Mechanisms. 1. Termination and Propagation Kinetics in Thiol-Ene PhotopolymerizationsReddy, Sirish K.; Cramer, Neil B.; Bowman, Christopher N.Macromolecules (2006), 39 (10), 3673-3680CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)In this work, termination and propagation kinetics of thiol-ene photopolymns. are investigated via unsteady-state anal., and termination is shown to occur though bimol. radical-radical recombinations. The termination rate is too rapid to be resolved by std. differential scanning calorimetry (DSC) or Fourier transform IR spectroscopy (FTIR) unsteady-state techniques. However, a modified rotating sector technique is demonstrated to be a viable technique for the quantification of the av. radical lifetimes in thiol-ene systems. The application of the rotating sector technique to thiol-ene polymns. requires extensive theor. developments and anal. that are also presented here. Kinetic parameters in thiol-ene systems are detd. by utilizing the exptl. knowledge of av. radical lifetimes and anal. expressions for steady-state and unsteady-state polymns. Knowledge of individual rate parameters in binary thiol-ene systems, rather than ratios of rate parameters, is essential for the prediction of polymn. kinetics in complex thiol-ene systems.
- 24Northrop, B. H.; Coffey, R. N. Thiol-ene click chemistry: computational and kinetic analysis of the influence of alkene functionality. J. Am. Chem. Soc. 2012, 134, 13804– 13817, DOI: 10.1021/ja305441dGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFalurzO&md5=d348da35492ec1591adedaa20bf23f41Thiol-Ene Click Chemistry: Computational and Kinetic Analysis of the Influence of Alkene FunctionalityNorthrop, Brian H.; Coffey, Roderick N.Journal of the American Chemical Society (2012), 134 (33), 13804-13817CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The influence of alkene functionality on the energetics and kinetics of radical initiated thiolene click chem. has been studied computationally at the CBS-QB3 level. Relative energetics (ΔH°, ΔH⧺, ΔG°, ΔG⧺) have been detd. for all stationary points along the step-growth mechanism of thiol-ene reactions between Me mercaptan and a series of 12 alkenes: propene, Me vinyl ether, Me allyl ether, norbornene, acrylonitrile, Me acrylate, butadiene, methyl(vinyl)silanediamine, Me crotonate, di-Me fumarate, styrene, and maleimide. Electronic structure calcns. reveal the underlying factors that control activation barriers for propagation and chain-transfer processes of the step-growth mechanism. Results are further extended to predict rate consts. for forward and reverse propagation and chain-transfer steps (kP, k-P, kCT, k-CT) and used to model overall reaction kinetics. A relationship between alkene structure and reactivity in thiol-ene reactions is derived from the results of kinetic modeling and can be directly related to the relative energetics of stationary points obtained from electronic structure calcns. The results predict the order of reactivity of alkenes and have broad implications for the use and applications of thiol-ene click chem.
- 25Cramer, N. B.; Davies, T.; O’Brien, A. K.; Bowman, C. N. Mechanism and modeling of a thiol-ene photopolymerization. Macromolecules 2003, 36, 4631– 4636, DOI: 10.1021/ma034072xGoogle Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjvVags78%253D&md5=0dfeb95c7a65d0113ca5babd8f75ad1dMechanism and Modeling of a Thiol-Ene PhotopolymerizationCramer, Neil B.; Davies, Tanner; O'Brien, Allison K.; Bowman, Christopher N.Macromolecules (2003), 36 (12), 4631-4636CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Thiol-ene photopolymns. proceed via a sequential radical propagation/chain transfer mechanism that leads to polymer and network formation much like a step growth polymn. Here, the chain transfer step in this sequential reaction series is shown to be the rate-limiting step. A model has been developed that accurately predicts the obsd. polymn. kinetic behavior under a variety of circumstances. Chain transfer is modeled as a rate-limiting step with the rate parameter (kp) for the propagation reaction being a factor of 10 greater than that for the chain transfer process (kCT) (kp/kCT = 10). The polymn. rate is first-order overall with first-order dependence on thiol functional group concn. and independent of the ene functional group concn.; Rp .varies. [SH]1[C:C]0. Polymn. rate behavior vs functional group concn. change is shown to be only a function of the ratio of propagation to chain transfer kinetic parameters.
- 26Shin, J.; Matsushima, H.; Comer, C. M.; Bowman, C. N.; Hoyle, C. E. Thiol-isocyanate-ene ternary networks by sequential and simultaneous thiol click reactions. Chem. Mater. 2010, 22, 2616– 2625, DOI: 10.1021/cm903856nGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXislyksLc%253D&md5=a8eb01cc3a7c7f50add56167d782543cThiol-Isocyanate-Ene Ternary Networks by Sequential and Simultaneous Thiol Click ReactionsShin, Junghwan; Matsushima, Hironori; Comer, Christopher M.; Bowman, Christopher N.; Hoyle, Charles E.Chemistry of Materials (2010), 22 (8), 2616-2625CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Thiol-isocyanate-ene ternary networks with systematic variations (100/100/0, 100/80/20, 100/60/40, 100/40/60, 100/20/80, and 100/0/100) were prepd. by sequential and simultaneous thiol-ene and thiol-isocyanate click reactions. The thiol-isocyanate coupling reaction was triggered thermally or photolytically to control the sequence with the thiol-ene photopolymn. Tri-Et amine (TEA) and 2,2-dimethoxy-2-Ph acetophenone (DMPA) were used for the sequential thermally induced thiol-isocyanate coupling and photochem. initiated thiol-ene reaction, resp. A thermally stable photolatent base catalyst (tributylamine·tetraphenylborate salt, TBA·HBPh4) capable of in situ generation of tributylamine by UV light was used with isopropylthioxanthone (ITX) for the simultaneous thiol-isocyanate/thiol-ene curing systems. The kinetics of the hybrid networks investigated using real-time IR indicate that both thiol-isocyanate and thiol-ene reactions were quant. rapid and efficient (>90% of conversion in a matter of minutes and seconds, resp.). The Tg of the thiourethane/thiol-ene hybrid networks progressively increases (-5° to 35° by DSC) as a function of the thiourethane content due to the higher extent of hydrogen bonding, also resulting in enhanced mech. properties. S Highly uniform and dense network structures exhibiting narrow full width at half-max. (∼10°) were obtained for both the sequential and the simultaneous thiol click reactions, resulting in identical thermal properties that are independent of the sequence of the curing processes.
- 27Cramer, N. B.; Bowman, C. N. Kinetics of thiol – ene and thiol – acrylate photopolymerizations with real-time Fourier transform infrared. J. Polym. Sci., Part A: Polym. Chem. 2001, 39, 3311– 3319, DOI: 10.1002/pola.1314Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXmslSjtbc%253D&md5=047b425b585b73c597f68bd14a0215e5Kinetics of thiol-ene and thiol-acrylate photopolymerizations with real-time fourier transform infraredCramer, Neil B.; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2001), 39 (19), 3311-3319CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)We used real-time Fourier transform IR to monitor the conversion of both thiol and ene (vinyl) functional groups independently during photoinduced thiol-ene photopolymns. From these results, the stoichiometry of various thiol-ene and thiol-acrylate polymns. was detd. For thiol-ene polymns., the conversion of ene functional groups was up to 15% greater than the conversion of thiol functional groups. For stoichiometric thiol-acrylate polymns., the conversion of the acrylate functional groups was roughly twice that of the thiol functional groups. With kinetic expressions for thiol-acrylate polymns., the acrylate propagation kinetic const. was 1.5 times greater than the rate const. for hydrogen abstraction from the thiol. Conversions of thiol-acrylate systems of various initial stoichiometries were successfully predicted with this ratio of propagation and chain-transfer kinetic consts. Thiol-acrylate systems with different initial stoichiometries exhibited diverse network properties. Thiol-ene systems were initiated with benzophenone and 2,2-dimethoxy-2-phenylacetophenone as initiators and were also polymd. without a photoinitiator.
- 28Cramer, N. B.; Reddy, S. K.; O’Brien, A. K.; Bowman, C. N. Thiol-ene photopolymerization mechanism and rate limiting step changes for various vinyl functional group chemistries. Macromolecules 2003, 36, 7964– 7969, DOI: 10.1021/ma034667sGoogle Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXnsFyqtbk%253D&md5=e0109a772f48cb8a0f9d24c6c6f9e25eThiol-Ene Photopolymerization Mechanism and Rate Limiting Step Changes for Various Vinyl Functional Group ChemistriesCramer, Neil B.; Reddy, Sirish K.; O'Brien, Allison K.; Bowman, Christopher N.Macromolecules (2003), 36 (21), 7964-7969CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)The mechanism and kinetics of thiol-ene photopolymns. utilizing a tetrafunctional thiol monomer copolymd. with acrylate, norbornene, vinyl ether, and vinyl silazane functionalized ene monomers are successfully modeled and exptl. characterized. Modeling predictions demonstrate that the reaction orders in thiol-ene systems are controlled by the ratio of thiyl radical propagation to chain transfer kinetic parameters (kp/kCT). Ratios of kinetic parameters (kp/kCT) were found to vary significantly with the ene functional group chem. and to have a dramatic impact on polymn. kinetics. For high ratios of kp/kCT, polymn. rates are first order in thiol functional group concn. and nearly independent of ene functional group concn. For kp/kCT values near unity, polymn. rates are approx. 1/2 order in both thiol and ene functional group concns. When kCT is much greater than kp, polymn. rates are first order in ene functional group concn. and nearly independent of the thiol functional group concn. In thiol-allyl ether and thiol-acrylate systems, the step growth polymn. rates are first order in thiol functional group concn. (Rp .varies. [SH]). For thiol-norbornene and thiol-vinyl ether systems, polymns. are nearly 1/2 order in both thiol and ene functional group concns. (Rp .varies. [SH]1/2[C:C]1/2). In thiol-vinyl silazane systems, polymn. rates are approx. first order in ene functional group concn. (Rp .varies. [C:C]) and independent of thiol functional group concn. A theory is proposed which states that the effect of functional group chem. on kp/kCT is controlled primarily by ene functional group electron d. (kp) and carbon radical stability (kCT).
- 29Reddy, S. K.; Cramer, N. B.; Bowman, C. N. Thiol-vinyl mechanisms. 2. kinetic modeling of ternary thiol-vinyl photopolymerizations. Macromolecules 2006, 39, 3681– 3687, DOI: 10.1021/ma0600097Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xjtlartb4%253D&md5=3a86eb554dba2e166408fd8a4105877fThiol-Vinyl Mechanisms. 2. Kinetic Modeling of Ternary Thiol-Vinyl PhotopolymerizationsReddy, Sirish K.; Cramer, Neil B.; Bowman, Christopher N.Macromolecules (2006), 39 (10), 3681-3687CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A framework is developed to understand and predict the photopolymn. kinetics of ternary thiol-vinyl systems: thiol-ene-ene and thiol-ene-acrylate. Ternary thiol-vinyl photopolymn. systems of thiol-allyl ether-norbornene, thiol-vinyl ether-norbornene, and thiol-vinyl ether-acrylate monomer mixts. are exptl. characterized and successfully modeled. The kinetic rate parameters employed for modeling are exptl. obtained from rotating sector unsteady-state anal. and rate mechanisms of the corresponding binary mixts. In thiol-ene-ene systems, the relative consumption of the ene functional groups is shown to be proportional to the resp. propagation kinetic parameters of the ene monomers and independent of the chain transfer kinetic parameters. In the thiol-ene-acrylate systems that exhibit a mixed step-chain growth mechanism, the relative conversion of monomers is shown to depend on both the propagation and chain transfer kinetic parameters.
- 30Bordoni, A. V.; Lombardo, M. V.; Regazzoni, A. E.; Soler-Illia, G. J. A. A.; Wolosiuk, A. Simple thiol-ene click chemistry modification of sba-15 silica pores with carboxylic acids. J. Colloid Interface Sci. 2015, 450, 316– 324, DOI: 10.1016/j.jcis.2015.03.030Google ScholarThere is no corresponding record for this reference.
- 31Liu, L.; Liu, Y.; Liu, Y.; Wang, Q. Efficient flame retardant polyvinyl alcohol membrane through surface graft method. RSC Adv. 2016, 6, 35051– 35057, DOI: 10.1039/C5RA27105CGoogle Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xksl2mtr0%253D&md5=40bf016a9e5db6f178f3fa7fe0da14b5Efficient flame retardant polyvinyl alcohol membrane through surface graft methodLiu, Li; Liu, Yuansen; Liu, Yuan; Wang, QiRSC Advances (2016), 6 (41), 35051-35057CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)The prepn. of flame retardant polyvinyl alc. (PVA) membranes with high performance is a challenge using conventional methods by phys. mixing flame retardants with a PVA soln. In this study, the surface grafting of a flame retardant on neat PVA membrane was adopted instead of conventional phys. mixing. The structure and grafting ratio of the flame retardant grafted chem. on a PVA membrane was examd. and characterized. A comparison of the performance between the surface grafted and the conventional mixed flame retardant PVA membranes were conducted by cone calorimetry, vertical flame, thermo-gravimetric anal. (TGA), differential scanning calorimetry (DSC), mech. properties and transparency tests. The results showed that with the same flame retardant content, the one with the surface grafted had much better flame retardance, mech. properties and transparence, as well as an enhanced melt point and thermal stability. In conclusion, the surface grafting of the flame retardant PVA membrane is very promising for many applications due to its remarkably improved properties.
- 32Vadala, M. L.; Thompson, M. S.; Ashworth, M. A.; Lin, Y.; Vadala, T. P.; Ragheb, R.; Riffle, J. S. Heterobifunctional poly(ethylene oxide) oligomers containing carboxylic acids. Biomacromolecules 2008, 9, 1035– 1043, DOI: 10.1021/bm701067dGoogle Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsVKls7Y%253D&md5=ee615fe94948e99706ccf84bff1cb278Heterobifunctional Poly(ethylene oxide) Oligomers Containing Carboxylic AcidsVadala, M. L.; Thompson, M. S.; Ashworth, M. A.; Lin, Y.; Vadala, T. P.; Ragheb, R.; Riffle, J. S.Biomacromolecules (2008), 9 (3), 1035-1043CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)Syntheses of vinylsilyl alcs. having one to three vinyl moieties and their use as initiators for ethylene oxide polymns. are discussed. Poly(ethylene oxide) oligomers with vinylsilanes at one end and a hydroxyl group at the other were prepd. in base-catalyzed reactions. Poly(ethylene oxide) oligomers with vinylsilanes at one end and a hydroxyl group at the other were prepd. in base-catalyzed reactions. Mol. wts. detd. from 1H NMR and gel permeation chromatog. were close to the targeted values. Carboxylic acid functional poly(ethylene oxide) oligomers were prepd. from ene-thiol addn. reactions of mercaptoacetic acid across the vinylsilane terminus. These carboxylic acid functional oligomers will complex to magnetite nanoparticles to afford complexes that can be dispersed in aq. media.
- 33Mondal, A. N.; Zheng, C.; Cheng, C.; Hossain, M. M.; Khan, M. I.; Yao, Z.; Wu, L.; Xu, T. Effect of novel polysiloxane functionalized poly(amps-co-cea) membranes for base recovery from alkaline waste solutions via diffusion dialysis. RSC Adv. 2015, 5, 95256– 95267, DOI: 10.1039/C5RA19415FGoogle Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslemsr%252FN&md5=999f687dece87910157014990a9993e5Effect of novel polysiloxane functionalized poly(AMPS-co-CEA) membranes for base recovery from alkaline waste solutions via diffusion dialysisMondal, Abhishek N.; Zheng, Chunlei; Cheng, Congliang; Hossain, Md. Masem; Khan, Muhammad Imran; Yao, Zilu; Wu, Liang; Xu, TongwenRSC Advances (2015), 5 (115), 95256-95267CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)In the modern arena of sepn. science and technol., cation exchange membrane (CEM) based diffusion dialysis (DD) has attracted remarkable attention due to its unique ion transport phenomena during applications for base recovery. In this manuscript, for the first time we reveal novel disodium 4-formylbenzene-1,3-disulfonate modified polysiloxane (FSP) induced poly(AMPS-co-CEA) based CEMs with polyvinyl alc. (PVA) as a binder and tetraethoxysilane (TEOS) acting as a crosslinker for base recovery via diffusion dialysis. Synthesis of poly(AMPS-co-CEA) involved classical free radical polymn. with azobisisobutyronitrile (AIBN) acting as an initiator. By regulating the dosage of FSP in the membrane matrix, the physiochem. as well as the electrochem. properties of the prepd. membranes can be modified. The prepd. membranes were investigated comprehensively in terms of water uptake (WR), ion exchange capacity (IEC) along with thermo-mech. measurements like DMA and TGA. The effect of FSP was discussed in brief to correlate the base recovery behavior of the prepd. membranes. The prepd. CEMs have water uptakes (WR) in the range 204.0-248.7%, ion exchange capacities (IEC) between 0.58 and 0.76 mmol g-1, tensile strengths (TS) between 9.3 and 15.9 MPa as well as elongations at break (Eb) of 125.6-236.7%. At 25 °C, the dialysis coeff. (UOH) values appeared as high as 0.0078-0.0112 m h-1 and the sepn. factors (S) ranged from 10.32 to 14.19. The membranes described in this manuscript could be a promising contender for base recovery via diffusion dialysis.
- 34Kim, C.-H.; Parkin, S.; Bharara, M.; Atwood, D. Linear coordination of hg(ii) by cysteamine. Polyhedron 2002, 21, 225– 228, DOI: 10.1016/S0277-5387(01)00978-0Google ScholarThere is no corresponding record for this reference.
- 35Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Noncovalent synthesis: using physical-organic chemistry to make aggregates. Acc. Chem. Res. 1995, 28, 37– 44, DOI: 10.1021/ar00049a006Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXjtF2rs7w%253D&md5=9ccd793bec440969f260e26ff3ac2180Noncovalent Synthesis: Using Physical-Organic Chemistry To Make AggregatesWhitesides, George M.; Simanek, Eric E.; Mathias, John P.; Seto, Christopher T.; Chin, Donovan; Mammen, Mathai; Gordon, Dana M.Accounts of Chemical Research (1995), 28 (1), 37-44CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review with 33 refs. Some of the concepts of noncovalent synthesis are illustrated with aggregates derived from the cyanuric acid-melamine lattice.
- 36Love, D. M.; Kim, K.; Goodrich, J. T.; Fairbanks, B. D.; Worrell, B. T.; Stoykovich, M. P.; Musgrave, C. B.; Bowman, C. N. Amine induced retardation of the radical-mediated thiol-ene reaction via the formation of metastable disulfide radical anions. J. Org. Chem. 2018, 83, 2912– 2919, DOI: 10.1021/acs.joc.8b00143Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXit1Whsbo%253D&md5=c40afe9da2928ef67ebf36d17bd94014Amine Induced Retardation of the Radical-Mediated Thiol-Ene Reaction via the Formation of Metastable Disulfide Radical AnionsLove, Dillon M.; Kim, Kangmin; Goodrich, John T.; Fairbanks, Benjamin D.; Worrell, Brady T.; Stoykovich, Mark P.; Musgrave, Charles B.; Bowman, Christopher N.Journal of Organic Chemistry (2018), 83 (5), 2912-2919CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)The effect of amines on the kinetics and efficacy of radical-mediated thiol-ene coupling (TEC) reactions was investigated. By varying the thiol reactant and amine additive, it was shown that amines retard thiyl radical-mediated reactions when the amine is adequately basic enough to deprotonate the thiol affording the thiolate anion, e.g., when the weakly basic amine tetramethylethylenediamine was incorporated in the TEC reaction between Bu 2-mercaptoacetate and an allyl ether at 5 mol %, the final conversion was reduced from quant. to <40%. Alternatively, no effect is obsd. when the less acidic thiol Bu 3-mercaptopropionate is employed. The thiolate anion was established as the retarding species through the introduction of ammonium and thiolate salt additives into TEC formulations. The formation of a two-sulfur three-electron bonded disulfide radical anion (DRA) species by the reaction of a thiyl radical with a thiolate anion was detd. as the cause for the redn. in catalytic radicals and the TEC rate. Thermodn. and kinetic trends in DRA formations were computed using d. functional theory and by modeling the reaction as an associative electron transfer process. These trends correlate well with the exptl. retardation trends of various thiolate anions in TEC reactions.
- 37Reddy, S. K.; Sebra, R. P.; Anseth, K. S.; Bowman, C. N. Living radical photopolymerization induced grafting on thiol-ene based substrates. J. Polym. Sci., Part A: Polym. Chem. 2005, 43, 2134– 2144, DOI: 10.1002/pola.20693Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXktVWjt7g%253D&md5=ad61b5b6536d3f4b0e6c7e53a4f129e2Living radical photopolymerization induced grafting on thiol-ene based substratesReddy, Sirish K.; Sebra, Robert P.; Anseth, Kristi S.; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2005), 43 (10), 2134-2144CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)The formation of reactive substrates with iniferter-mediated living radical photopolymn. is a powerful technique for surface modification, which can readily be used to facilitate the incorporation of a variety of surface functionalities. In this research, the photopolymn. kinetics of novel bulk thiol-ene systems have been compared with those of typical acrylate and methacrylate systems when polymd. in the presence of the photoiniferter p-xylene bis(N,N-di-Et dithiocarbamate) (XDT). In the presence of XDT, the thiol-ene systems photopolymerize more quickly than the traditional acrylate and methacrylate systems by one to two orders of magnitude. Fourier transform IR spectroscopy has been used to monitor the photografting kinetics of various monomers on dithiocarbamate-functionalized surfaces. Furthermore, this technique has been used to evaluate surface-initiation kinetics and to emphasize the influence of bulk substrate properties on grafting kinetics. Finally, photopatterning has been demonstrated on a dithiocarbamate-incorporated thiol-ene substrate with conventional photolithog. techniques.
- 38Cramer, N. B.; Reddy, S. K.; Lu, H.; Cross, T.; Raj, R.; Bowman, C. N. Thiol-ene photopolymerization of polymer-derived ceramic precursors. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 1752– 1757, DOI: 10.1002/pola.20010Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXitlWntrg%253D&md5=41638f969b6e0de463b6a09cef0d17e4Thiol-ene photopolymerization of polymer-derived ceramic precursorsCramer, Neil B.; Reddy, Sirish K.; Lu, Hui; Cross, Tsali; Raj, Rishi; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2004), 42 (7), 1752-1757CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)The liq., ceramic precursor monomer VL20 was copolymd. with a thiol monomer in a traditional radical thiol-ene photopolymn. Polymn. occurred via addn. of the thiol functional group to the vinyl silazane functional group in a 1:1 ratio consistent with a step-growth polymn. Gelation occurred at a high conversion of functional groups (70%) consistent with an av. mol. wt. and functionality of 560 and 1.7, resp., for VL20 monomers. Initiatorless photopolymn. of the thiol-VL20 system also occurred upon irradn. at either 365 or 254 nm.
- 39Feng, W.; Li, L.; Ueda, E.; Li, J.; Heißler, S.; Welle, A.; Trapp, O.; Levkin, P. A. Surface patterning via thiol-yne click chemistry: an extremely fast and versatile approach to superhydrophilic-superhydrophobic micropatterns. Adv. Mater. Interfaces 2014, 1, 1400269 DOI: 10.1002/admi.201400269Google ScholarThere is no corresponding record for this reference.
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Abstract
Figure 1
Figure 1. (A) Scheme for the simplified mechanism of the photoinitiated thiol–ene coupling reaction catalyzed by the addition of a chemical photoinitiator (PI). (22) (B) Schemes of the two reactions in this report.
Figure 2
Figure 2. (A) 1H NMR spectra of the reactant mixture of VTMS, TGA, and DMPA in CDCl3, before (red trace) and after (blue trace) exposure to the solar simulator for 300 s. (B) 1H NMR spectra of the reactant mixture of VTMS, CAH, and DMPA in (CD3)2CO–D2O (1:4 v/v) co-solvent, before (red trace) and after (blue trace) exposure to the solar simulator for 150 s. (C, D) 1H NMR spectra of control experiments of the unexposed reaction mixtures of (C) VTMS with TGA showing no change in the vinyl and thiol peaks, and (D) VTMS with CAH also showing no change in the vinyl peak without UV light exposure.
Figure 3
Figure 3. (A) Reaction kinetics in bulk solution containing VTMS, TGA, and DMPA in CDCl3 measured by 1H NMR. The sample was exposed to 368–400 nm light for specific time intervals (0, 9, 14, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 120, 180, and 300 s) prior to each 1H NMR measurement. (B) Similar experiments performed on a reaction mixture containing VTMS, CAH, and DMPA in (CD3)2CO–D2O co-solvent (1:4 v/v) and at time intervals of 0, 5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 90, and 150 s.
Figure 4
Figure 4. (A) Selected NMR spectra of the reaction mixture of TGA, VTMS, and DMPA in CDCl3 focusing on the vinyl (red), thiol (black), and product (green and blue) regions from Figure 3. (B) Plots of integrated peak areas of the color-coded regions shown in (A). The scatter plots are integrated peak areas after each exposure time for each of the corresponding peaks in (A), which are fitted with the models described in the text. (C) Selected NMR spectra of the reaction mixture of CAH, VTMS, and DMPA in (CD3)2CO–D2O (1:4 v/v) co-solvent focusing on the vinyl (red) and product (green and blue) regions. (D) Plots of integrated peak areas of the color-coded regions shown in (C), where the scatter plots and solid traces represent integrated peak areas and fitted curves, respectively. These curves were fitted using eqs 11–13.
References
This article references 39 other publications.
- 1Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click chemistry: diverse chemical function from a few good reactions. Angew. Chem., Int. Ed. 2001, 40, 2004– 2021, DOI: 10.1002/1521-3773(20010601)40:113.0.CO;2-51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXksVOis78%253D&md5=61c28b416c42c87821bc8a5bc2fdec36Click chemistry: diverse chemical function from a few good reactionsKolb, Hartmuth C.; Finn, M. G.; Sharpless, K. BarryAngewandte Chemie, International Edition (2001), 40 (11), 2004-2021CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)Review with > 88 refs. Examn. of nature's favorite mols. reveals a striking preference for making carbon-heteroatom bonds over carbon-carbon bonds - surely no surprise given that carbon dioxide is nature's starting material and that most reactions are performed in water. Nucleic acids, proteins, and polysaccharides are condensation polymers of small subunits stitched together by carbon-heteroatom bonds. Even the 35 or so building blocks from which these crucial mols. are made each contain, at most, six contiguous C-C bonds, except for the three arom. amino acids. Taking a cue from nature's approach, the development of a set of powerful, highly reliable, and selective reactions for the rapid synthesis of useful new compds. and combinatorial libraries through heteroatom links (C-X-C), an approach called "click chem." is addressed. Click chem. is at once defined, enabled, and constrained by a handful of nearly perfect "spring-loaded" reactions. The stringent criteria for a process to earn click chem. status are described along with examples of the mol. frameworks that are easily made using this spartan, but powerful, synthetic strategy.
- 2Hoyle, C. E.; Lowe, A. B.; Bowman, C. N. Thiol-click chemistry: a multifaceted toolbox for small molecule and polymer synthesis. Chem. Soc. Rev. 2010, 39, 1355– 1387, DOI: 10.1039/b901979k2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjs1Ggu74%253D&md5=b5ea504263dbe971aa2017061552c15bThiol-click chemistry: a multifaceted toolbox for small molecule and polymer synthesisHoyle, Charles E.; Lowe, Andrew B.; Bowman, Christopher N.Chemical Society Reviews (2010), 39 (4), 1355-1387CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The merits of thiol-click chem. and its potential for making new forays into chem. synthesis and materials applications are described. Since thiols react to high yields under benign conditions with a vast range of chem. species, their utility extends to a large no. of applications in the chem., biol., phys., materials and engineering fields. This crit. review provides insight into emerging venues for application as well as new mechanistic understanding of this exceptional chem. in its many forms (81 refs.).
- 3Melnik, E.; Muellner, P.; Bethge, O.; Bertagnolli, E.; Hainberger, R.; Laemmerhofer, M. Streptavidin binding as a model to characterize thiol–ene chemistry-based polyamine surfaces for reversible photonic protein biosensing. Chem. Commun. 2014, 50, 2424– 2427, DOI: 10.1039/c3cc48640kThere is no corresponding record for this reference.
- 4Melnik, E. V. A.; Bruck, R.; Hainberger, R.; Lämmerhofer, M. Multi-step surface functionalization of polyimide based evanescent wave photonic biosensors and application for dna hybridization by Mach-Zehnder interferometer. Anal. Chim. Acta 2011, 699, 206– 215, DOI: 10.1016/j.aca.2011.05.017There is no corresponding record for this reference.
- 5Skinner, E. K.; Whiffin, F. M.; Price, G. J. Room temperature sonochemical initiation of thiol-ene reactions. Chem. Commun. 2012, 48, 6800– 6802, DOI: 10.1039/c2cc32457a5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XotleksL8%253D&md5=67cbb749ef68498eb2828ea847536d3bRoom temperature sonochemical initiation of thiol-ene reactionsSkinner, Emily K.; Whiffin, Fraeya M.; Price, Gareth J.Chemical Communications (Cambridge, United Kingdom) (2012), 48 (54), 6800-6802CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)Thiol-ene 'click' reactions have been initiated for a range of primary alkenes using ultrasound in both toluene and water. The method is particularly effective in aq. solns. in the presence of air.
- 6Taghavikish, M.; Subianto, S.; Dutta, N.; Roy Choudhury, N. Novel thiol-ene hybrid coating for metal protection. Coatings 2016, 6, 17, DOI: 10.3390/coatings6020017There is no corresponding record for this reference.
- 7Kade, M. J.; Burke, D. J.; Hawker, C. J. The power of thiol-ene chemistry. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 743– 750, DOI: 10.1002/pola.238247https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXntlahug%253D%253D&md5=100eb92de04ae4f4a8b5e26bc20b4fbfThe power of thiol-ene chemistryKade, Matthew J.; Burke, Daniel J.; Hawker, Craig J.Journal of Polymer Science, Part A: Polymer Chemistry (2010), 48 (4), 743-750CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)A review. As a tribute to Professor Charlie Hoyle, we take the opportunity to review the impact of thiol-ene chem. on polymer and materials science over the past 5 years. During this time, a renaissance in thiol-ene chem. has occurred with recent progress demonstrating its unique advantages when compared with traditional coupling and functionalization strategies. Addnl., the robust nature of thiol-ene chem. allows for the prepn. of well-defined materials with few structural limitations and synthetic requirements. To illustrate these features, the utility of thiol-ene reactions for network formation, polymer functionalization, dendrimer synthesis, and the decoration of three-dimensional objects is discussed. Also, the development of the closely related thiol-yne chem. is described. 2010 Wiley Periodicals, Inc., J Polym Sci Part A: Polym Chem 48: 743-750, 2010.
- 8Hoyle, C. E.; Bowman, C. N. Thiol-ene click chemistry. Angew. Chem., Int. Ed. 2010, 49, 1540– 1573, DOI: 10.1002/anie.2009039248https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXisVaktr8%253D&md5=0c104f1f1df66670742b1430ac01d1daThiol-Ene Click ChemistryHoyle, Charles E.; Bowman, Christopher N.Angewandte Chemie, International Edition (2010), 49 (9), 1540-1573CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Following Sharpless' visionary characterization of several idealized reactions as click reactions, the materials science and synthetic chem. communities have pursued numerous routes toward the identification and implementation of these click reactions. Herein, the authors review the radical-mediated thiol-ene reaction as one such click reaction. This reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Further, the thiol-ene reaction is most frequently photoinitiated, particularly for photopolymns. resulting in highly uniform polymer networks, promoting unique capabilities related to spatial and temporal control of the click reaction. The reaction mechanism and its implementation in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymn. are all reviewed.
- 9Lowe, A. B. Thiol-ene “ click ” reactions and recent applications in polymer and materials synthesis: a first update. Polym. Chem. 2014, 5, 4820– 4870, DOI: 10.1039/C4PY00339J9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1ektrnN&md5=0ee49a0e502b2e82e5cec0b9b4c9e408Thiol-ene "click" reactions and recent applications in polymer and materials synthesis: a first updateLowe, Andrew B.Polymer Chemistry (2014), 5 (17), 4820-4870CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)A review. This contribution serves as an update to a previous review (Polym. Chem. 2010, 1, 17-36) and highlights recent applications of thiol-ene 'click' chem. as an efficient tool for both polymer/materials synthesis as well as modification. This current contribution covers examples from the literature published up to ca. mid 2013. It is not intended to be exhaustive but rather serves to highlight many of the new and exciting applications where researchers have applied thiol-ene chem. in advanced macromol. engineering and materials chem.
- 10Grim, J. C.; Marozas, I. A.; Anseth, K. S. Thiol-ene and photo-cleavage chemistry for controlled presentation of biomolecules in hydrogels. J. Controlled Release 2015, 219, 95– 106, DOI: 10.1016/j.jconrel.2015.08.04010https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVWgu73I&md5=a49d2f3c6406686e5998f453a3b2f1c9Thiol-ene and photo-cleavage chemistry for controlled presentation of biomolecules in hydrogelsGrim, Joseph C.; Marozas, Ian A.; Anseth, Kristi S.Journal of Controlled Release (2015), 219 (), 95-106CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)Hydrogels have emerged as promising scaffolds in regenerative medicine for the delivery of biomols. to promote healing. However, increasing evidence suggests that the context that biomols. are presented to cells (e.g., as sol. verses tethered signals) can influence their bioactivity. A common approach to deliver biomols. in hydrogels involves phys. entrapping them within the network, such that they diffuse out over time to the surrounding tissues. While simple and versatile, the release profiles in such system are highly dependent on the mol. wt. of the entrapped mol. relative to the network structure, and it can be difficult to control the release of two different signals at independent rates. In some cases, supraphysiol. high loadings are used to achieve therapeutic local concns., but uncontrolled release can then cause deleterious off-target side effects. In vivo, many growth factors and cytokines are stored in the extracellular matrix (ECM) and released on demand as needed during development, growth, and wound healing. Thus, emerging strategies in biomaterial chem. have focused on ways to tether or sequester biol. signals and engineer these bioactive scaffolds to signal to delivered cells or endogenous cells. While many strategies exist to achieve tethering of peptides, protein, and small mols., this review focuses on photochem. methods, and their usefulness as a mild reaction that proceeds with fast kinetics in aq. solns. and at physiol. conditions. Photo-click and photo-caging methods are particularly useful because one can direct light to specific regions of the hydrogel to achieve spatial patterning. Recent methods have even demonstrated reversible introduction of biomols. to mimic the dynamic changes of native ECM, enabling researchers to explore how the spatial and dynamic context of biomol. signals influences important cell functions. This review will highlight how two photochem. methods have led to important advances in the tissue regeneration community, namely the thiol-ene photo-click reaction for bioconjugation and photocleavage reactions that allow for the removal of protecting groups. Specific examples will be highlighted where these methodologies have been used to engineer hydrogels that control and direct cell function with the aim of inspiring their use in regenerative medicine.
- 11McKenas, C. G.; Fehr, J. M.; Donley, C. L.; Lockett, M. R. Thiol-ene modified amorphous carbon substrates: surface patterning and chemically modified electrode preparation. Langmuir 2016, 32, 10529– 10536, DOI: 10.1021/acs.langmuir.6b0296111https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFGrsrrF&md5=73a4ddf4392855ec6c2803f20b3a8ca9Thiol-Ene Modified Amorphous Carbon Substrates: Surface Patterning and Chemically Modified Electrode PreparationMcKenas, Catherine G.; Fehr, Julia M.; Donley, Carrie L.; Lockett, Matthew R.Langmuir (2016), 32 (41), 10529-10536CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)There are a no. of wet chem. methods capable of tailoring the reactivity and wettability of amorphous carbon (aC) films, but few of these chemistries are compatible with photopatterning. The authors introduce a method to install thiol groups directly onto the surface of aC films. These terminal thiols are compatible with thiol-ene click reactions, which allowed us to rapidly functionalize and pattern the surface of the aC films. The aC films were characterized and it was confirmed that the installation of surface-bound thiols did not significantly oxidize the surface or change its topog. The authors detd. the conditions needed to selectively attach alkene-contg. mols. to these films and show the reaction is proceeding through a thiol-mediated reaction. The utility of this approach was demonstrated by photopatterning the aC films and prepg. ferrocene-modified aC electrodes.
- 12Wendeln, C.; Rinnen, S.; Schulz, C.; Arlinghaus, H. F.; Ravoo, B. J. Photochemical microcontact printing by thiol-ene and thiol-yne click chemistry. Langmuir 2010, 26, 15966– 15971, DOI: 10.1021/la102966j12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtFygt7vE&md5=b68f5e961c2078f219f644e5aa628fc0Photochemical Microcontact Printing by Thiol-Ene and Thiol-Yne Click ChemistryWendeln, Christian; Rinnen, Stefan; Schulz, Christian; Arlinghaus, Heinrich F.; Ravoo, Bart JanLangmuir (2010), 26 (20), 15966-15971CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)This article describes the microstructured immobilization of functional thiols on alkene- and alkyne-terminated self-assembled monolayers on silicon oxide substrates by photochem. microcontact printing. A photochem. thiol-ene or thiol-yne "click" reaction was locally induced in the area of contact between stamp and substrate by irradn. with UV light (365 nm). The immobilization reaction by photochem. microcontact printing was verified by contact angle measurements, XPS, at. force microscopy, and time-of-flight secondary ion mass spectrometry. The reaction rate of photochem. microcontact printing by thiol-ene chem. was studied using time dependent contact angle measurements. The selective binding of lectins to galactoside microarrays prepd. by photochem. microcontact printing was also demonstrated. It was found that photochem. microcontact printing results in a high surface coverage of functional thiols within 30 s of printing even for dil. (mM) ink solns.
- 13Wu, J.-T.; Huang, C.; Liang, W.; Wu, Y.; Yu, J.; Chen, H. Reactive polymer coatings: a general route to thiol-ene and thiol-yne click reactions. Macromol. Rapid Commun. 2012, 33, 922– 927, DOI: 10.1002/marc.20120001113https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XisFajtrY%253D&md5=f8b2124c4427f0faba085f53083fb931Reactive Polymer Coatings: A General Route to Thiol-ene and Thiol-yne Click ReactionsWu, Jyun-Ting; Huang, Chi-Hui; Liang, Wei-Chieh; Wu, Yen-Lin; Yu, Jiashing; Chen, Hsien-YehMacromolecular Rapid Communications (2012), 33 (10), 922-927CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)Reactive polymer coatings were synthesized via chem. vapor deposition (CVD) polymn. process. These coatings decouple surface design from bulk properties of underlying materials and provide a facile and general route to support thiol-ene and thiol-yne reactions on a variety of substrate materials. Through the reported technique, surface functions can be activated through a simple design of thiol-terminated mols. such as polyethylene glycols (PEGs) or peptides (GRGDYC), and the according biol. functions were demonstrated in controlled and low-fouling protein adsorptions as well as accurately manipulated cell attachments.
- 14Cole, M. A.; Bowman, C. N. Evaluation of thiol-ene click chemistry in functionalized polysiloxanes. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 1749– 1757, DOI: 10.1002/pola.2655114https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhsVaqtrs%253D&md5=214614fa6376267e17d54a82c2c39a51Evaluation of thiol-ene click chemistry in functionalized polysiloxanesCole, Megan A.; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2013), 51 (8), 1749-1757CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)Polysiloxanes are commonly used in a myriad of applications, and the "click" nature of the thiol-ene reaction is well suited for introducing alternative functionalities or for crosslinking these ubiquitous polymers. As such, understanding of the thiol-ene reaction in the presence of silicones is valuable and would lead to enhanced methodologies for modification and crosslinking. Here, the thiol-ene reaction kinetics were investigated in functionalized oligosiloxanes having varying degrees of thiol functionalization (SH), π-π interactions (from diphenyls, DP), and ene types (C=C). In the ene-functionalized oligomers, π-π interactions were controlled through the use of dioctyl repeats (DO). The polymn. rate and rate-limiting steps were detd. for all systems contg. an allyl-functionalized oligomer, and rates ranging from 0.10 to 0.54 mol L-1 min-1 were seen. The rate-limiting step varied with the oligomer compn.; examples of rate-limited propagation (5:3:2 C=C:DP:DO/1:1 SH:DP) or chain transfer (5:3:2 C=C:DP:DO/3:1 SH:DP) were found in addn. to cases with similar reaction rate consts. (5:2:3 C=C:DP:DO/1:1 SH:DP). None of the siloxanes were found to exhibit autoacceleration despite their relatively high viscosities. Instead, the allyl-, vinyl-, and acrylate-functionalized siloxanes were all found to undergo unimol. termination based on their high α scaling values (0.98, 0.95, and 0.82, resp.) in the relation Rp .varies. Riα. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013.
- 15Li, Z.; Zhu, Z.; Chueh, C.-C.; Luo, J.; Jen, A. K.-Y. Facile thiol-ene thermal crosslinking reaction facilitated hole-transporting layer for highly efficient and stable perovskite solar cells. Adv. Energy Mater. 2016, 6, 1601165 DOI: 10.1002/aenm.201601165There is no corresponding record for this reference.
- 16Chan, J. W.; Hoyle, C. E.; Lowe, A. B.; Bowman, M. Nucleophile-initiated thiol-Michael reactions: effect of organocatalyst, thiol, and ene. Macromolecules 2010, 43, 6381– 6388, DOI: 10.1021/ma101069c16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXoslehsrk%253D&md5=95aca849447e21d8549b47a07994490eNucleophile-Initiated Thiol-Michael Reactions: Effect of Organocatalyst, Thiol, and EneChan, Justin W.; Hoyle, Charles E.; Lowe, Andrew B.; Bowman, MarkMacromolecules (Washington, DC, United States) (2010), 43 (15), 6381-6388CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A detailed evaluation of the kinetics of the thiol-Michael reaction between hexanethiol and hexyl acrylate is described. It is shown that primary amines are more effective catalysts than either secondary or tertiary amines with, for example, quant. conversion being achieved within 500 s in the case of hexylamine with an apparent rate const. of 53.4 mol L-1 s-1 at a catalyst loading of 0.057 mol %. Certain tertiary phosphines, and esp. tri-n-propylphosphine and dimethylphenylphosphine, are shown to be even more effective species even at concns. 2 orders of magnitude lower than employed for hexylamine and performed in soln. with quant. conversions reached within ca. 100 s for both species and apparent rate consts. of 1810 and 431 mol L-1 s-1, resp. The nature of the thiol is also demonstrated to be an important consideration with mercaptoglycolate and mercaptopropionate esters being significantly more reactive than hexanethiol with reactivity mirroring the pKa of the thiols. Likewise, it is shown that the structure of the activated ene is also crucial with the degree of activation and ene-substitution pattern being important features in detg. reactivity. In terms of reaction with hexanethiol in the presence of hexylamine as catalyst, it is shown that propylmaleimide > di-Et fumarate > di-Et maleate > dimethylacrylamide > acrylonitrile > Et crotonate > Et cinnamate > Et methacrylate.
- 17Nair, D. P.; Podgórski, M.; Chatani, S.; Gong, T.; Xi, W.; Fenoli, C. R.; Bowman, C. N. The thiol-michael addition click reaction: a powerful and widely used tool in materials chemistry. Chem. Mater. 2014, 26, 724– 744, DOI: 10.1021/cm402180t17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXht12ht7vK&md5=d48828084a19cdfc3634693ca9feed6fThe thiol-Michael addition click reaction. A powerful and widely used tool in materials chemistryNair, Devatha P.; Podgorski, Maciej; Chatani, Shunsuke; Gong, Tao; Xi, Weixian; Fenoli, Christopher R.; Bowman, Christopher N.Chemistry of Materials (2014), 26 (1), 724-744CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)A review. The key attribute of the thiol-Michael addn. reaction that makes it a prized tool in materials science is its modular click nature, which allows for the implementation of this highly efficient, green reaction in applications that vary from small mol. synthesis to in situ polymer modifications in biol. systems to the surface functionalization of material coatings. Over the past few decades, interest in the thiol-Michael addn. reaction increased dramatically, as is evidenced by the no. of studies that were dedicated to elucidating different aspects of the reaction that range from an in-depth anal. aimed at understanding the mechanistic pathways of the reaction to synthetic studies that have examd. modifying mol. structures with the aim of yielding highly efficient thiol-Michael reaction monomers. This review examd. the reaction mechanisms, the substrates and catalysts used in the reaction, and the subsequent implementation of the thiol-Michael reaction in materials science over the years, with particular emphasis on the recent developments in the arena over the past decade.
- 18Hoyle, C. E.; Lee, T. Y.; Roper, T. Thiol-enes: chemistry of the past with promise for the future. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 5301– 5338, DOI: 10.1002/pola.2036618https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXptVKgsrs%253D&md5=1dddaa64f77f7f79c3f9e49333cf693cThiol-enes: Chemistry of the past with promise for the futureHoyle, Charles E.; Lee, Tai Yeon; Roper, ToddJournal of Polymer Science, Part A: Polymer Chemistry (2004), 42 (21), 5301-5338CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)A review. The photopolymn. of mixts. of multifunctional thiols and enes is an efficient method for the rapid prodn. of films and thermoset plastics with unprecedented phys. and mech. properties. One of the major obstacles in traditional free-radical photopolymn. is essentially eliminated in thiol-ene polymns. because the polymn. occurs in air almost as rapidly as in an inert atm. Virtually any type of ene will participate in a free-radical polymn. process with a multifunctional thiol. Hence, it is possible to tailor materials with virtually any combination of properties required for a particular application.
- 19Derboven, P.; D’hooge, D. R.; Stamenovic, M. M.; Espeel, P.; Marin, G. B.; Du Prez, F. E.; Reyniers, M.-F. Kinetic modeling of radical thiol–ene chemistry for macromolecular design: importance of side reactions and diffusional limitations. Macromolecules 2013, 46, 1732– 1742, DOI: 10.1021/ma302619k19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXivVyhtrY%253D&md5=7d7dd04bb4828f46263e8551a5dfe30bKinetic Modeling of Radical Thiol-Ene Chemistry for Macromolecular Design: Importance of Side Reactions and Diffusional LimitationsDerboven, Pieter; D'hooge, Dagmar R.; Stamenovic, Milan M.; Espeel, Pieter; Marin, Guy B.; Du Prez, Filip E.; Reyniers, Marie-FrancoiseMacromolecules (Washington, DC, United States) (2013), 46 (5), 1732-1742CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)The radical thiol-ene coupling of thiol-functionalized polystyrene (PS-SH) with dodecyl vinyl ether (DVE) and the polystyrene-b-poly(vinyl acetate) (PS-b-PVAc) polymer-polymer conjugation using 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator are modeled to assess the importance of diffusional limitations and side reactions. Intrinsic chem. rate coeffs. are detd. based on a kinetic study of the coupling of benzyl thiol (BT) and DVE. The addn. and transfer reactions are chem. controlled, whereas diffusional limitations on termination slightly increase the coupling efficiency. Termination by recombination of carbon-centered radicals and addn. of DMPA derived radicals to DVE are shown to be mainly responsible for the reduced coupling efficiency in case polymeric species are involved. The obtained results confirm the idea to disregard radical thiol-ene chem. as a true member of the family of "click" chem. techniques for polymer-polymer conjugation and show that the initial conditions have a significant impact on the coupling efficiency.
- 20Okay, O.; Bowman, C. N. Kinetic modeling of thiol-ene reactions with both step and chain growth aspects. Macromol. Theory Simul. 2005, 14, 267– 277, DOI: 10.1002/mats.20050000220https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXkslyktLk%253D&md5=ca6031bbf325aa31849c6c2311e621a4Kinetic modeling of thiol-ene reactions with both step and chain growth aspectsOkay, Oguz; Bowman, Christopher N.Macromolecular Theory and Simulations (2005), 14 (4), 267-277CODEN: MTHSEK; ISSN:1022-1344. (Wiley-VCH Verlag GmbH & Co. KGaA)A kinetic model is presented for thiol-ene crosslinking photopolymns. including the allowance for chain growth reaction of the ene, i.e., homopolymn. The kinetic model is based on a description of the av. chain lengths derived from differential equations of the type of Smoluchowski coagulation equations. The method of moments was applied to obtain av. properties of thiolene reaction systems. The model predicts the mol. wt. distribution of active and inactive species in the pregel regime of thiol-enes, as well as the gel points depending on the synthesis parameters. It is shown that, when no homopolymn. is allowed, the av. mol. wts. and the gel point conversion are given by the typical equations valid for the step-growth polymn. Increasing the extent of homopolymn. also increases the av. mol. wts. and shifts the gel point toward lower conversions and shorter reaction times. It is also shown that the ratio of thiyl radical propagation to the chain transfer kinetic parameter (Kp1/Ktr) affects the gelation time, tcr. Gelation occurs earlier as the Kp1/Ktr ratio is increased due to the predominant attack of thiyl radicals on the vinyl groups and formation of more stable carbon radicals. The gel point in thiol-ene reactions is also found to be very sensitive to the extent of cyclization, particularly, if the monomer functionalities are low.
- 21Bordoni, A. V.; Lombardo, M. V.; Wolosiuk, A. Photochemical radical thiol–ene click-based methodologies for silica and transition metal oxides materials chemical modification: a mini-review. RSC Adv. 2016, 6, 77410– 77426, DOI: 10.1039/C6RA10388J21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1OkurbM&md5=df0afa33ac5ca783ac47ef78a9d7c3aaPhotochemical radical thiol-ene click-based methodologies for silica and transition metal oxides materials chemical modification: a mini-reviewBordoni, Andrea V.; Lombardo, M. Veronica; Wolosiuk, AlejandroRSC Advances (2016), 6 (81), 77410-77426CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)Although known for more than 40 years in the polymer chem. field, the photochem. radical thiol-ene addn. (PRTEA) has been recently recognized as a chem. reaction with click characteristics. Photoinitiation enables spatial and temporal control of this highly efficient reaction, bridging simple org. chem. with high-end materials synthesis and surfaces functionalization. In this minireview, we focus on the latest contributions based on the PRTEA for the synthesis of chem. precursors for silica and transition metal oxides (TMO) based materials. We summarize the mechanism of the PRTEA, the development of new families of photoinitiators and how this extremely simple approach has spilled over into the materials science arena with clear success. In particular, PRTEA adds to the collective efforts for building a reliable and straightforward chem. toolbox for surface modification and the prodn. of sol-gel precursors, nanoparticles and thin films. The excellent perspectives for simple mol. and supramol. building block synthesis opens up a rational synthetic route for the design and integration of these components in multipurpose platforms.
- 22Fairbanks, B. D.; Love, D. M.; Bowman, C. N. Efficient polymer-polymer conjugation via thiol-ene click reaction. Macromol. Chem. Phys. 2017, 218, 1700073 DOI: 10.1002/macp.201700073There is no corresponding record for this reference.
- 23Reddy, S. K.; Cramer, N. B.; Bowman, C. N. Thiol-vinyl mechanisms. 1. termination and propagation kinetics in thiol-ene photopolymerizations. Macromolecules 2006, 39, 3673– 3680, DOI: 10.1021/ma060008e23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XjtlartLc%253D&md5=0f319d58709c6af5f8832dd5baf33320Thiol-Vinyl Mechanisms. 1. Termination and Propagation Kinetics in Thiol-Ene PhotopolymerizationsReddy, Sirish K.; Cramer, Neil B.; Bowman, Christopher N.Macromolecules (2006), 39 (10), 3673-3680CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)In this work, termination and propagation kinetics of thiol-ene photopolymns. are investigated via unsteady-state anal., and termination is shown to occur though bimol. radical-radical recombinations. The termination rate is too rapid to be resolved by std. differential scanning calorimetry (DSC) or Fourier transform IR spectroscopy (FTIR) unsteady-state techniques. However, a modified rotating sector technique is demonstrated to be a viable technique for the quantification of the av. radical lifetimes in thiol-ene systems. The application of the rotating sector technique to thiol-ene polymns. requires extensive theor. developments and anal. that are also presented here. Kinetic parameters in thiol-ene systems are detd. by utilizing the exptl. knowledge of av. radical lifetimes and anal. expressions for steady-state and unsteady-state polymns. Knowledge of individual rate parameters in binary thiol-ene systems, rather than ratios of rate parameters, is essential for the prediction of polymn. kinetics in complex thiol-ene systems.
- 24Northrop, B. H.; Coffey, R. N. Thiol-ene click chemistry: computational and kinetic analysis of the influence of alkene functionality. J. Am. Chem. Soc. 2012, 134, 13804– 13817, DOI: 10.1021/ja305441d24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFalurzO&md5=d348da35492ec1591adedaa20bf23f41Thiol-Ene Click Chemistry: Computational and Kinetic Analysis of the Influence of Alkene FunctionalityNorthrop, Brian H.; Coffey, Roderick N.Journal of the American Chemical Society (2012), 134 (33), 13804-13817CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The influence of alkene functionality on the energetics and kinetics of radical initiated thiolene click chem. has been studied computationally at the CBS-QB3 level. Relative energetics (ΔH°, ΔH⧺, ΔG°, ΔG⧺) have been detd. for all stationary points along the step-growth mechanism of thiol-ene reactions between Me mercaptan and a series of 12 alkenes: propene, Me vinyl ether, Me allyl ether, norbornene, acrylonitrile, Me acrylate, butadiene, methyl(vinyl)silanediamine, Me crotonate, di-Me fumarate, styrene, and maleimide. Electronic structure calcns. reveal the underlying factors that control activation barriers for propagation and chain-transfer processes of the step-growth mechanism. Results are further extended to predict rate consts. for forward and reverse propagation and chain-transfer steps (kP, k-P, kCT, k-CT) and used to model overall reaction kinetics. A relationship between alkene structure and reactivity in thiol-ene reactions is derived from the results of kinetic modeling and can be directly related to the relative energetics of stationary points obtained from electronic structure calcns. The results predict the order of reactivity of alkenes and have broad implications for the use and applications of thiol-ene click chem.
- 25Cramer, N. B.; Davies, T.; O’Brien, A. K.; Bowman, C. N. Mechanism and modeling of a thiol-ene photopolymerization. Macromolecules 2003, 36, 4631– 4636, DOI: 10.1021/ma034072x25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjvVags78%253D&md5=0dfeb95c7a65d0113ca5babd8f75ad1dMechanism and Modeling of a Thiol-Ene PhotopolymerizationCramer, Neil B.; Davies, Tanner; O'Brien, Allison K.; Bowman, Christopher N.Macromolecules (2003), 36 (12), 4631-4636CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Thiol-ene photopolymns. proceed via a sequential radical propagation/chain transfer mechanism that leads to polymer and network formation much like a step growth polymn. Here, the chain transfer step in this sequential reaction series is shown to be the rate-limiting step. A model has been developed that accurately predicts the obsd. polymn. kinetic behavior under a variety of circumstances. Chain transfer is modeled as a rate-limiting step with the rate parameter (kp) for the propagation reaction being a factor of 10 greater than that for the chain transfer process (kCT) (kp/kCT = 10). The polymn. rate is first-order overall with first-order dependence on thiol functional group concn. and independent of the ene functional group concn.; Rp .varies. [SH]1[C:C]0. Polymn. rate behavior vs functional group concn. change is shown to be only a function of the ratio of propagation to chain transfer kinetic parameters.
- 26Shin, J.; Matsushima, H.; Comer, C. M.; Bowman, C. N.; Hoyle, C. E. Thiol-isocyanate-ene ternary networks by sequential and simultaneous thiol click reactions. Chem. Mater. 2010, 22, 2616– 2625, DOI: 10.1021/cm903856n26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXislyksLc%253D&md5=a8eb01cc3a7c7f50add56167d782543cThiol-Isocyanate-Ene Ternary Networks by Sequential and Simultaneous Thiol Click ReactionsShin, Junghwan; Matsushima, Hironori; Comer, Christopher M.; Bowman, Christopher N.; Hoyle, Charles E.Chemistry of Materials (2010), 22 (8), 2616-2625CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Thiol-isocyanate-ene ternary networks with systematic variations (100/100/0, 100/80/20, 100/60/40, 100/40/60, 100/20/80, and 100/0/100) were prepd. by sequential and simultaneous thiol-ene and thiol-isocyanate click reactions. The thiol-isocyanate coupling reaction was triggered thermally or photolytically to control the sequence with the thiol-ene photopolymn. Tri-Et amine (TEA) and 2,2-dimethoxy-2-Ph acetophenone (DMPA) were used for the sequential thermally induced thiol-isocyanate coupling and photochem. initiated thiol-ene reaction, resp. A thermally stable photolatent base catalyst (tributylamine·tetraphenylborate salt, TBA·HBPh4) capable of in situ generation of tributylamine by UV light was used with isopropylthioxanthone (ITX) for the simultaneous thiol-isocyanate/thiol-ene curing systems. The kinetics of the hybrid networks investigated using real-time IR indicate that both thiol-isocyanate and thiol-ene reactions were quant. rapid and efficient (>90% of conversion in a matter of minutes and seconds, resp.). The Tg of the thiourethane/thiol-ene hybrid networks progressively increases (-5° to 35° by DSC) as a function of the thiourethane content due to the higher extent of hydrogen bonding, also resulting in enhanced mech. properties. S Highly uniform and dense network structures exhibiting narrow full width at half-max. (∼10°) were obtained for both the sequential and the simultaneous thiol click reactions, resulting in identical thermal properties that are independent of the sequence of the curing processes.
- 27Cramer, N. B.; Bowman, C. N. Kinetics of thiol – ene and thiol – acrylate photopolymerizations with real-time Fourier transform infrared. J. Polym. Sci., Part A: Polym. Chem. 2001, 39, 3311– 3319, DOI: 10.1002/pola.131427https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXmslSjtbc%253D&md5=047b425b585b73c597f68bd14a0215e5Kinetics of thiol-ene and thiol-acrylate photopolymerizations with real-time fourier transform infraredCramer, Neil B.; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2001), 39 (19), 3311-3319CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)We used real-time Fourier transform IR to monitor the conversion of both thiol and ene (vinyl) functional groups independently during photoinduced thiol-ene photopolymns. From these results, the stoichiometry of various thiol-ene and thiol-acrylate polymns. was detd. For thiol-ene polymns., the conversion of ene functional groups was up to 15% greater than the conversion of thiol functional groups. For stoichiometric thiol-acrylate polymns., the conversion of the acrylate functional groups was roughly twice that of the thiol functional groups. With kinetic expressions for thiol-acrylate polymns., the acrylate propagation kinetic const. was 1.5 times greater than the rate const. for hydrogen abstraction from the thiol. Conversions of thiol-acrylate systems of various initial stoichiometries were successfully predicted with this ratio of propagation and chain-transfer kinetic consts. Thiol-acrylate systems with different initial stoichiometries exhibited diverse network properties. Thiol-ene systems were initiated with benzophenone and 2,2-dimethoxy-2-phenylacetophenone as initiators and were also polymd. without a photoinitiator.
- 28Cramer, N. B.; Reddy, S. K.; O’Brien, A. K.; Bowman, C. N. Thiol-ene photopolymerization mechanism and rate limiting step changes for various vinyl functional group chemistries. Macromolecules 2003, 36, 7964– 7969, DOI: 10.1021/ma034667s28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXnsFyqtbk%253D&md5=e0109a772f48cb8a0f9d24c6c6f9e25eThiol-Ene Photopolymerization Mechanism and Rate Limiting Step Changes for Various Vinyl Functional Group ChemistriesCramer, Neil B.; Reddy, Sirish K.; O'Brien, Allison K.; Bowman, Christopher N.Macromolecules (2003), 36 (21), 7964-7969CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)The mechanism and kinetics of thiol-ene photopolymns. utilizing a tetrafunctional thiol monomer copolymd. with acrylate, norbornene, vinyl ether, and vinyl silazane functionalized ene monomers are successfully modeled and exptl. characterized. Modeling predictions demonstrate that the reaction orders in thiol-ene systems are controlled by the ratio of thiyl radical propagation to chain transfer kinetic parameters (kp/kCT). Ratios of kinetic parameters (kp/kCT) were found to vary significantly with the ene functional group chem. and to have a dramatic impact on polymn. kinetics. For high ratios of kp/kCT, polymn. rates are first order in thiol functional group concn. and nearly independent of ene functional group concn. For kp/kCT values near unity, polymn. rates are approx. 1/2 order in both thiol and ene functional group concns. When kCT is much greater than kp, polymn. rates are first order in ene functional group concn. and nearly independent of the thiol functional group concn. In thiol-allyl ether and thiol-acrylate systems, the step growth polymn. rates are first order in thiol functional group concn. (Rp .varies. [SH]). For thiol-norbornene and thiol-vinyl ether systems, polymns. are nearly 1/2 order in both thiol and ene functional group concns. (Rp .varies. [SH]1/2[C:C]1/2). In thiol-vinyl silazane systems, polymn. rates are approx. first order in ene functional group concn. (Rp .varies. [C:C]) and independent of thiol functional group concn. A theory is proposed which states that the effect of functional group chem. on kp/kCT is controlled primarily by ene functional group electron d. (kp) and carbon radical stability (kCT).
- 29Reddy, S. K.; Cramer, N. B.; Bowman, C. N. Thiol-vinyl mechanisms. 2. kinetic modeling of ternary thiol-vinyl photopolymerizations. Macromolecules 2006, 39, 3681– 3687, DOI: 10.1021/ma060009729https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xjtlartb4%253D&md5=3a86eb554dba2e166408fd8a4105877fThiol-Vinyl Mechanisms. 2. Kinetic Modeling of Ternary Thiol-Vinyl PhotopolymerizationsReddy, Sirish K.; Cramer, Neil B.; Bowman, Christopher N.Macromolecules (2006), 39 (10), 3681-3687CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A framework is developed to understand and predict the photopolymn. kinetics of ternary thiol-vinyl systems: thiol-ene-ene and thiol-ene-acrylate. Ternary thiol-vinyl photopolymn. systems of thiol-allyl ether-norbornene, thiol-vinyl ether-norbornene, and thiol-vinyl ether-acrylate monomer mixts. are exptl. characterized and successfully modeled. The kinetic rate parameters employed for modeling are exptl. obtained from rotating sector unsteady-state anal. and rate mechanisms of the corresponding binary mixts. In thiol-ene-ene systems, the relative consumption of the ene functional groups is shown to be proportional to the resp. propagation kinetic parameters of the ene monomers and independent of the chain transfer kinetic parameters. In the thiol-ene-acrylate systems that exhibit a mixed step-chain growth mechanism, the relative conversion of monomers is shown to depend on both the propagation and chain transfer kinetic parameters.
- 30Bordoni, A. V.; Lombardo, M. V.; Regazzoni, A. E.; Soler-Illia, G. J. A. A.; Wolosiuk, A. Simple thiol-ene click chemistry modification of sba-15 silica pores with carboxylic acids. J. Colloid Interface Sci. 2015, 450, 316– 324, DOI: 10.1016/j.jcis.2015.03.030There is no corresponding record for this reference.
- 31Liu, L.; Liu, Y.; Liu, Y.; Wang, Q. Efficient flame retardant polyvinyl alcohol membrane through surface graft method. RSC Adv. 2016, 6, 35051– 35057, DOI: 10.1039/C5RA27105C31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xksl2mtr0%253D&md5=40bf016a9e5db6f178f3fa7fe0da14b5Efficient flame retardant polyvinyl alcohol membrane through surface graft methodLiu, Li; Liu, Yuansen; Liu, Yuan; Wang, QiRSC Advances (2016), 6 (41), 35051-35057CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)The prepn. of flame retardant polyvinyl alc. (PVA) membranes with high performance is a challenge using conventional methods by phys. mixing flame retardants with a PVA soln. In this study, the surface grafting of a flame retardant on neat PVA membrane was adopted instead of conventional phys. mixing. The structure and grafting ratio of the flame retardant grafted chem. on a PVA membrane was examd. and characterized. A comparison of the performance between the surface grafted and the conventional mixed flame retardant PVA membranes were conducted by cone calorimetry, vertical flame, thermo-gravimetric anal. (TGA), differential scanning calorimetry (DSC), mech. properties and transparency tests. The results showed that with the same flame retardant content, the one with the surface grafted had much better flame retardance, mech. properties and transparence, as well as an enhanced melt point and thermal stability. In conclusion, the surface grafting of the flame retardant PVA membrane is very promising for many applications due to its remarkably improved properties.
- 32Vadala, M. L.; Thompson, M. S.; Ashworth, M. A.; Lin, Y.; Vadala, T. P.; Ragheb, R.; Riffle, J. S. Heterobifunctional poly(ethylene oxide) oligomers containing carboxylic acids. Biomacromolecules 2008, 9, 1035– 1043, DOI: 10.1021/bm701067d32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsVKls7Y%253D&md5=ee615fe94948e99706ccf84bff1cb278Heterobifunctional Poly(ethylene oxide) Oligomers Containing Carboxylic AcidsVadala, M. L.; Thompson, M. S.; Ashworth, M. A.; Lin, Y.; Vadala, T. P.; Ragheb, R.; Riffle, J. S.Biomacromolecules (2008), 9 (3), 1035-1043CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)Syntheses of vinylsilyl alcs. having one to three vinyl moieties and their use as initiators for ethylene oxide polymns. are discussed. Poly(ethylene oxide) oligomers with vinylsilanes at one end and a hydroxyl group at the other were prepd. in base-catalyzed reactions. Poly(ethylene oxide) oligomers with vinylsilanes at one end and a hydroxyl group at the other were prepd. in base-catalyzed reactions. Mol. wts. detd. from 1H NMR and gel permeation chromatog. were close to the targeted values. Carboxylic acid functional poly(ethylene oxide) oligomers were prepd. from ene-thiol addn. reactions of mercaptoacetic acid across the vinylsilane terminus. These carboxylic acid functional oligomers will complex to magnetite nanoparticles to afford complexes that can be dispersed in aq. media.
- 33Mondal, A. N.; Zheng, C.; Cheng, C.; Hossain, M. M.; Khan, M. I.; Yao, Z.; Wu, L.; Xu, T. Effect of novel polysiloxane functionalized poly(amps-co-cea) membranes for base recovery from alkaline waste solutions via diffusion dialysis. RSC Adv. 2015, 5, 95256– 95267, DOI: 10.1039/C5RA19415F33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslemsr%252FN&md5=999f687dece87910157014990a9993e5Effect of novel polysiloxane functionalized poly(AMPS-co-CEA) membranes for base recovery from alkaline waste solutions via diffusion dialysisMondal, Abhishek N.; Zheng, Chunlei; Cheng, Congliang; Hossain, Md. Masem; Khan, Muhammad Imran; Yao, Zilu; Wu, Liang; Xu, TongwenRSC Advances (2015), 5 (115), 95256-95267CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)In the modern arena of sepn. science and technol., cation exchange membrane (CEM) based diffusion dialysis (DD) has attracted remarkable attention due to its unique ion transport phenomena during applications for base recovery. In this manuscript, for the first time we reveal novel disodium 4-formylbenzene-1,3-disulfonate modified polysiloxane (FSP) induced poly(AMPS-co-CEA) based CEMs with polyvinyl alc. (PVA) as a binder and tetraethoxysilane (TEOS) acting as a crosslinker for base recovery via diffusion dialysis. Synthesis of poly(AMPS-co-CEA) involved classical free radical polymn. with azobisisobutyronitrile (AIBN) acting as an initiator. By regulating the dosage of FSP in the membrane matrix, the physiochem. as well as the electrochem. properties of the prepd. membranes can be modified. The prepd. membranes were investigated comprehensively in terms of water uptake (WR), ion exchange capacity (IEC) along with thermo-mech. measurements like DMA and TGA. The effect of FSP was discussed in brief to correlate the base recovery behavior of the prepd. membranes. The prepd. CEMs have water uptakes (WR) in the range 204.0-248.7%, ion exchange capacities (IEC) between 0.58 and 0.76 mmol g-1, tensile strengths (TS) between 9.3 and 15.9 MPa as well as elongations at break (Eb) of 125.6-236.7%. At 25 °C, the dialysis coeff. (UOH) values appeared as high as 0.0078-0.0112 m h-1 and the sepn. factors (S) ranged from 10.32 to 14.19. The membranes described in this manuscript could be a promising contender for base recovery via diffusion dialysis.
- 34Kim, C.-H.; Parkin, S.; Bharara, M.; Atwood, D. Linear coordination of hg(ii) by cysteamine. Polyhedron 2002, 21, 225– 228, DOI: 10.1016/S0277-5387(01)00978-0There is no corresponding record for this reference.
- 35Whitesides, G. M.; Simanek, E. E.; Mathias, J. P.; Seto, C. T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Noncovalent synthesis: using physical-organic chemistry to make aggregates. Acc. Chem. Res. 1995, 28, 37– 44, DOI: 10.1021/ar00049a00635https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXjtF2rs7w%253D&md5=9ccd793bec440969f260e26ff3ac2180Noncovalent Synthesis: Using Physical-Organic Chemistry To Make AggregatesWhitesides, George M.; Simanek, Eric E.; Mathias, John P.; Seto, Christopher T.; Chin, Donovan; Mammen, Mathai; Gordon, Dana M.Accounts of Chemical Research (1995), 28 (1), 37-44CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review with 33 refs. Some of the concepts of noncovalent synthesis are illustrated with aggregates derived from the cyanuric acid-melamine lattice.
- 36Love, D. M.; Kim, K.; Goodrich, J. T.; Fairbanks, B. D.; Worrell, B. T.; Stoykovich, M. P.; Musgrave, C. B.; Bowman, C. N. Amine induced retardation of the radical-mediated thiol-ene reaction via the formation of metastable disulfide radical anions. J. Org. Chem. 2018, 83, 2912– 2919, DOI: 10.1021/acs.joc.8b0014336https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXit1Whsbo%253D&md5=c40afe9da2928ef67ebf36d17bd94014Amine Induced Retardation of the Radical-Mediated Thiol-Ene Reaction via the Formation of Metastable Disulfide Radical AnionsLove, Dillon M.; Kim, Kangmin; Goodrich, John T.; Fairbanks, Benjamin D.; Worrell, Brady T.; Stoykovich, Mark P.; Musgrave, Charles B.; Bowman, Christopher N.Journal of Organic Chemistry (2018), 83 (5), 2912-2919CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)The effect of amines on the kinetics and efficacy of radical-mediated thiol-ene coupling (TEC) reactions was investigated. By varying the thiol reactant and amine additive, it was shown that amines retard thiyl radical-mediated reactions when the amine is adequately basic enough to deprotonate the thiol affording the thiolate anion, e.g., when the weakly basic amine tetramethylethylenediamine was incorporated in the TEC reaction between Bu 2-mercaptoacetate and an allyl ether at 5 mol %, the final conversion was reduced from quant. to <40%. Alternatively, no effect is obsd. when the less acidic thiol Bu 3-mercaptopropionate is employed. The thiolate anion was established as the retarding species through the introduction of ammonium and thiolate salt additives into TEC formulations. The formation of a two-sulfur three-electron bonded disulfide radical anion (DRA) species by the reaction of a thiyl radical with a thiolate anion was detd. as the cause for the redn. in catalytic radicals and the TEC rate. Thermodn. and kinetic trends in DRA formations were computed using d. functional theory and by modeling the reaction as an associative electron transfer process. These trends correlate well with the exptl. retardation trends of various thiolate anions in TEC reactions.
- 37Reddy, S. K.; Sebra, R. P.; Anseth, K. S.; Bowman, C. N. Living radical photopolymerization induced grafting on thiol-ene based substrates. J. Polym. Sci., Part A: Polym. Chem. 2005, 43, 2134– 2144, DOI: 10.1002/pola.2069337https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXktVWjt7g%253D&md5=ad61b5b6536d3f4b0e6c7e53a4f129e2Living radical photopolymerization induced grafting on thiol-ene based substratesReddy, Sirish K.; Sebra, Robert P.; Anseth, Kristi S.; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2005), 43 (10), 2134-2144CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)The formation of reactive substrates with iniferter-mediated living radical photopolymn. is a powerful technique for surface modification, which can readily be used to facilitate the incorporation of a variety of surface functionalities. In this research, the photopolymn. kinetics of novel bulk thiol-ene systems have been compared with those of typical acrylate and methacrylate systems when polymd. in the presence of the photoiniferter p-xylene bis(N,N-di-Et dithiocarbamate) (XDT). In the presence of XDT, the thiol-ene systems photopolymerize more quickly than the traditional acrylate and methacrylate systems by one to two orders of magnitude. Fourier transform IR spectroscopy has been used to monitor the photografting kinetics of various monomers on dithiocarbamate-functionalized surfaces. Furthermore, this technique has been used to evaluate surface-initiation kinetics and to emphasize the influence of bulk substrate properties on grafting kinetics. Finally, photopatterning has been demonstrated on a dithiocarbamate-incorporated thiol-ene substrate with conventional photolithog. techniques.
- 38Cramer, N. B.; Reddy, S. K.; Lu, H.; Cross, T.; Raj, R.; Bowman, C. N. Thiol-ene photopolymerization of polymer-derived ceramic precursors. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 1752– 1757, DOI: 10.1002/pola.2001038https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXitlWntrg%253D&md5=41638f969b6e0de463b6a09cef0d17e4Thiol-ene photopolymerization of polymer-derived ceramic precursorsCramer, Neil B.; Reddy, Sirish K.; Lu, Hui; Cross, Tsali; Raj, Rishi; Bowman, Christopher N.Journal of Polymer Science, Part A: Polymer Chemistry (2004), 42 (7), 1752-1757CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)The liq., ceramic precursor monomer VL20 was copolymd. with a thiol monomer in a traditional radical thiol-ene photopolymn. Polymn. occurred via addn. of the thiol functional group to the vinyl silazane functional group in a 1:1 ratio consistent with a step-growth polymn. Gelation occurred at a high conversion of functional groups (70%) consistent with an av. mol. wt. and functionality of 560 and 1.7, resp., for VL20 monomers. Initiatorless photopolymn. of the thiol-VL20 system also occurred upon irradn. at either 365 or 254 nm.
- 39Feng, W.; Li, L.; Ueda, E.; Li, J.; Heißler, S.; Welle, A.; Trapp, O.; Levkin, P. A. Surface patterning via thiol-yne click chemistry: an extremely fast and versatile approach to superhydrophilic-superhydrophobic micropatterns. Adv. Mater. Interfaces 2014, 1, 1400269 DOI: 10.1002/admi.201400269There is no corresponding record for this reference.