ACS Publications. Most Trusted. Most Cited. Most Read
Quick View

OR SEARCH CITATIONS

My Activity
Publications
CONTENT TYPES

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:Macromolecules 2014, 47, 19, 6572-6579
RETURN TO ISSUEPREVArticleNEXT

A Bicyclo[4.2.0]octene-Derived Monomer Provides Completely Linear Alternating Copolymers via Alternating Ring-Opening Metathesis Polymerization (AROMP)

View Author Information
Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
*E-mail [email protected] (K.A.P.).
*E-mail [email protected] (N.S.S.).
Cite this: Macromolecules 2014, 47, 19, 6572–6579
Publication Date (Web):September 23, 2014
https://doi.org/10.1021/ma5012039
Copyright © 2014 American Chemical Society
RIGHTS & PERMISSIONS
ACS AuthorChoiceACS AuthorChoice

Article Views

2520

Altmetric

-

Citations

32
LEARN ABOUT THESE METRICS
PDF (1 MB)
Get e-Alerts
Supporting Info (1)»
SUBJECTS:

Abstract

High Resolution Image
Download MS PowerPoint Slide

Strained bicyclic carbomethoxy olefins were utilized as substrates in alternating ring-opening metathesis polymerization and found to provide low-dispersity polymers with novel backbones. The polymerization of methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate with cyclohexene in the presence of the fast-initiating Grubbs catalyst (H2IMes)(3-Br-Pyr)2Cl2Ru═CHPh leads to a completely linear as well as alternating copolymer, as demonstrated by NMR spectroscopy, isotopic labeling, and gel permeation chromatography. In contrast, intramolecular chain-transfer reactions were observed with [5.2.0] and [3.2.0] bicyclic carbomethoxy olefins, although to a lesser extent than with the previously reported monocyclic cyclobutenecarboxylic ester monomers [Song, A.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2009, 131, 3444]. Inclusion of cyclohexyl rings fused to the copolymer backbone minimizes intramolecular chain-transfer reactions and provides a framework for creating alternating functionality in a one-step polymerization.

In recent decades, copolymers have been widely studied for their uses in the biomedical and material sciences. (1-3) Block copolymers, already established as thermoplastic elastomers, detergents, cosmetics, and pharmaceutical preparations, promise to contribute to new applications based on nanoscale structures, membranes, and drug and gene delivery. (4) Much less explored are alternating copolymers. For applications in which two different polymer-borne moieties must interact (5-9) (e.g., as in organic light-emitting diodes and solar cells), alternating copolymers should impose consistently optimal positioning of the participating substituents.
Alternating copolymers are generally synthesized by radical polymerization in which the alternating order of addition of monomers at the end of the growing chain is kinetically controlled. (10-12) However, the conditions required for radical propagation are not compatible with a number of functional groups that might be desired in the polymer target. Furthermore, with some exceptions, (13-15) such polymerizations are generally not “living”. Therefore, they do not afford polymer products with narrow molecular weight distributions (low-molar-mass dispersities or DMs) that are advantageous for certain applications.
Living polymerizations based on the functional group-tolerant ruthenium metathesis catalysts have the potential to provide alternating copolymers that have low DMs and that bear a variety of functional groups. In metathesis, alternation of the incorporation of two monomers requires alternation of the affinities of the monomer A and monomer B to the living metal alkylidene. There are few solutions to this problem and consequently few examples of completely alternating metathesis copolymers. Rooney, (16-18) Chen, (19-22) and Blechert and Buchmeiser (23-25) have focused on the design of asymmetric catalysts that provide alternating selectivity for different pairs of monomers. Typically variation in steric bulk about the catalyst results in alternating reactivity of very strained and moderately strained, but more sterically demanding, monomers. Despite impressive catalyst designs, more than a 10-fold excess of the moderately strained monomer is required to maintain alternation. (22)
Monomer-design approaches take advantage of the different properties of two monomers such as polarity, (26) electron density and steric hindrance, (27) and acid–base interactions (28) and, in the latter two cases, provide perfectly alternating copolymers without use of excess monomer. Herein, we describe new pairs of monomers that generate, sequentially, two different ruthenium carbenes. One of these pairs efficiently provides completely alternating, linear copolymers.
We discovered that cyclobutene-1-carboxylate esters undergo ring-opening metathesis (ROM), but they do not undergo ROMP. (27) Nonetheless, in solution with cyclohexene (which also does not ROMP on its own), the cyclobutenecarboxylic esters participate in an alternating ring-opening metathesis polymerization (AROMP or altROMP). The high fidelity of the alternation in the chain extending steps can be attributed to the complementary reactivities of the two intermediate ruthenium carbenes. (29) There is a high kinetic barrier to cyclobutene ester homopolymerization, and the low ring strain of the cyclohexene monomer does not overcome the entropic penalty for its homopolymerization. (27) Moreover, the substitution of the cyclobutene alkene provides regiochemical and stereochemical control of the polymerization.
The molecular weight homogeneity of the copolymers resulting from our cyclohexene/1-cyclobutene ester pair was limited by “backbiting” reactions, intramolecular chain-transfers that lead to the formation of cyclic polymers, shortened chains, and compromised molar-mass dispersities (DMs). Indeed, we discovered that the use of the Hoveyda–Grubbs II catalysts, which favor cyclizations, resulted in the exclusive formation (within the limits of detection) of cyclic alternating copolymers. (30) Recently, we observed complete inhibition of backbiting upon introduction of bulky side chains into the AROMP monomers. However, the increased steric hindrance near the double bond slows the polymerization propagation rate, resulting in shorter polymers and thus limits the utility of this approach. (9)
Cognizant of the desirability of high-molecular-weight linear polymers with narrow molecular weight distributions, we set out to find a pair of monomers that would give longer and linear AROMP polymers with low-molar-mass dispersities. Here we report the results of this search to date.

Experimental Methods

ARTICLE SECTIONS
Jump To
All metathesis reactions were performed under an N2 atmosphere. Solvents, e.g. CH2Cl2 and benzene, were purified and dried in a GlassContour solvent push-still system. Deuterated solvents for all ring-opening reactions were degassed and filtered through basic alumina before use. [(H2IMes)(PCy3)(Cl)2Ru═CHPh] and ethyl 1-bromocyclobutane carboxylate were purchased from Aldrich. Cyclohexene-d10 was purchased from CDN Isotope Inc. The synthesis of Grubbs III catalyst, [(H2IMes)(3-Br-Pyr)2Cl2Ru═CHPh], was performed according to the procedure of Love et al. (31) A fresh stock solution of the Grubbs III catalyst (0.02 M for AROMP or 0.03 M for ROM, AROM-1, and AROM-2) and fresh stock solutions of monomers 3 and 4 (0.17–1.0 M for AROMP, depending on the desired length, or 0.03 M for ROM, AROM-1, and AROM-2) were prepared in CD2Cl2 for each of the NMR experiments.
Mallinckrodt silica gel 60 (230–400 mesh) was used for column chromatography. Analytical thin layer chromatography (TLC) was performed on precoated silica gel plates (60F254), chromatography on silica gel-60 (230–400 mesh), and Combi-Flash chromatography on RediSep normal phase silica columns (silica gel-60, 230–400 mesh). Varian Inova400, Inova500, Inova600 and Bruker Nanobay 400, Avance III 500, Avance III 700, Avance III-HD 850 MHz NMR instruments were used for analysis. Chemical shifts are denoted in ppm (δ) and calibrated from residual undeuterated solvents. The degree of polymerization (DP) of linear polymers was assessed by comparing the 1H NMR integration of the polymer alkene protons to that of the phenyl end group. Molecular weights and molar mass dispersities were measured with a gel phase chromatography system constructed from a Shimadzu pump coupled to a Shimadzu UV detector. CH2Cl2 served as the eluent with a flow rate of 0.700 mL/min on an American Polymer Standards column (Phenogel 5 μ MXL GPC column, Phenomenex). All GPCs were calibrated with poly(styrene) standards at 30 °C.

Bicyclo[2.2.1]hept-2-ene-2-carboxylic Acid (32, 33)

A modification of the two-step procedure of Elsheimer was followed. (32)Safety warning: CF2Br2 has a very low boiling point, and addition of CF2Br2 to norbornene is very exothermic. Therefore, for a large-scale reaction, this procedure should be carried out carefully behind a safety shield.

2-Bromo-3-(bromodifluoromethyl)bicyclo[2.2.1]heptanes

To a mixture of norbornene (6.10 g, 65 mmol), CuCl (0.99 g, 1 mmol), ethanolamine (3.00 g, 50 mmol), and tert-butyl alcohol (7.40 g, 100 mmol) in a 50 mL flask, CF2Br2 was slowly added (27.30 g, 130 mmol). The resulting mixture was protected from light and stirred at reflux (80–85 °C) for 48 h. Then it was cooled and diluted with deionized water (50 mL) and Et2O (25 mL). The Et2O layer was washed with H2O (5 × 25 mL) and dried over anhydrous Na2SO4. After filtration, the extract was concentrated and the residue was purified by flash column chromatography to yield a mixture of bicyclo[2.2.1]heptanes as a colorless oil (16.75 g, 87%). 1H NMR (500 MHz, CDCl3): δ 4.09 (d, J = 10 Hz, 1H), 2.78 (td, J = 15 Hz, 10 Hz, 1H), 2.71 (s, 1H), 2.68 (d, J = 10 Hz, 1H), 2.12 (d, J = 10 Hz, 1H), 1.76 (m, 1H), 1.64 (m, 1H), 1.40–1.20 (m, 3H).

Bicyclo[2.2.1]hept-2-ene-2-carboxylic Acid

In a screw-top vial under an N2 atmosphere, KOH (5.89 g, 10.5 mmol) was dissolved in deionized H2O (4 mL). A sample of 2-bromo-3-(bromodifluoromethyl)bicyclo[2.2.1]heptanes (0.776 g, 2.66 mmol) was added to the solution, and the mixture was heated at 130 °C in a microwave reactor at 20 bar for 2 h. Then the solution was cooled and washed with CHCl3 (2 × 4 mL), and the pH of the basic extract was adjusted to 2 with 3 N aqueous HCl. The aqueous solution was extracted with CHCl3 (3 × 4 mL), and the combined CHCl3 solution was dried over anhydrous Na2SO4 and concentrated in vacuo to give a brown oil. Purification by flash column chromatography (95:5/CH2Cl2:MeOH) yielded bicyclo[2.2.1]hept-2-ene-2-carboxylic acid as a colorless oil (160 mg, 50%).

Methyl Bicyclo[2.2.1]hept-2-ene-2-carboxylate, 2

The procedure of Mathias was followed. (33) Bicyclo[2.2.1]hept-2-ene-2-carboxylic acid (40 mg, 0.29 mmol) was treated with N,N-diisopropyl-O-methylisourea (180 mg, 1.16 mmol) in dry ether (5 mL) and stirred for 48 h. The urea byproduct precipitated at −20 °C, and it was removed by filtration. Removal of the solvent afforded a yellow oil which was purified by flash column chromatography (90:10/hexane:CH2Cl2) to yield ester 2 (26 mg, 58%). 1H NMR (400 MHz, CD2Cl2): δ 6.91 (d, J = 2.8 Hz, 1H), 3.72 (s, 3H), 3.26 (s, 1H), 3.02 (s, 1H), 1.75 (m, 2H), 1.48 (d, J = 8.4 Hz, 1H), 1.20 (d, J = 8.4 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 164.9, 146.6, 140.5, 51.0, 48.0, 43.4, 41.8, 24.5, 24.4.

General Procedure for the Synthesis of Bicyclo[n.2.0] Monomers

These monomers were prepared according to Snider’s approach; (34) the purification of monomer 4 was modified as noted. To a 50 mL flask with anhydrous AlCl3 powder under an N2 atmosphere was added dry benzene and methyl propiolate. The mixture was stirred until a homogeneous yellow solution formed. Cycloalkene was added, and the resulting mixture was stirred for 7 days. The reaction mixture was cooled in an ice bath and quenched with saturated NH4Cl solution. The precipitate was removed by filtering the resulting mixture through a pad of Celite. The filtrate was extracted with three portions of Et2O, and the combined Et2O extract was washed with brine and dried over anhydrous MgSO4. The solvent was removed in vacuo, and the crude product was subjected to flash column chromatography.

Methyl bicyclo[3.2.0]hept-6-ene-6-carboxylate, 3

AlCl3 (160 mg, 1.21 mmol, 0.5 equiv), methyl propiolate (204 mg, 2.42 mmol), and cyclopentene (170 μL, 2.90 mmol, 1.2 equiv) were stirred for 7 days in dry benzene (50 mL). Flash column chromatography of the crude product (30:70/hexane:CH2Cl2) yielded ester 3 (175 mg, 48% yield). 1H NMR (400 MHz, acetone-d6): δ 6.62 (br s, 1H), 3.69 (s, 3H), 3.33 (br dd, J = 3.2 Hz, 7.6 Hz, 1H), 3.06 (br dd, J = 3.6 Hz, 8.0 Hz, 1H), 1.78–1.21 (m, 6H). 13C NMR (100 MHz, CDCl3): δ 162.5, 147.5, 138.2, 51.1, 46.9, 44.5, 25.5, 25.4, 22.9.

Methyl Bicyclo[4.2.0]oct-7-ene-7-carboxylate, 4

AlCl3 (227 mg, 1.72 mmol, 0.86 equiv), methyl propiolate (168 mg, 2.00 mmol), and cyclohexene (263 μL, 2.60 mmol, 1.30 equiv) were stirred for 7 days in dry benzene (5 mL) and yielded a mixture of compound 4 and isomer methyl (E)-3-(cyclohex-1-enyl)propenoate in a ratio of 1:0.11–0.23. The mixture was treated with m-chloroperoxybenzoic acid (m-CPBA) to epoxidize the isomeric byproduct, followed by flash column chromatography (30:70/hexane:CH2Cl2) to provide bicyclic ester 4 (210 mg, 65% yield). 1H NMR (400 MHz, acetone-d6): δ 6.89 (d, J = 1.2 Hz, 1H), 3.71 (s, 3H), 3.07–3.04 (m, 1H), 2.80–2.77 (m, 1H), 2.00–1.30 (m, 8H). 13C NMR (100 MHz, CDCl3): δ 162.4, 150.1, 141.4, 50.7, 39.8, 38.1, 23.5, 23.3, 18.6, 18.0.

Methyl Bicyclo[5.2.0]non-8-ene-8-carboxylate, 5

AlCl3 (1.00 g, 7.56 mmol, 0.5 equiv), methyl propiolate (1.27 g, 15.2 mmol), and cycloheptene (2.16 mL, 18.2 mmol, 1.2 equiv) were stirred for 7 days in dry benzene (50 mL). Flash column chromatography of the crude product (30:70/hexane:CH2Cl2) yielded 5 (1.40 g, 50% yield). 1H NMR (400 MHz, CDCl3): δ 6.70 (d, J = 1 Hz, 1H), 3.61 (s, 3H), 2.99 (m, 1H), 2.77 (m, 1H), 1.77–1.21 (m, 10H). 13C NMR (100 MHz, CDCl3): δ 162.6, 148.9, 140.5, 50.6, 46.9, 45.4, 31.6, 29.1, 28.6, 27.9, 27.7.

General Procedure for NMR Scale AROMP Reactions

All kinetic experiments were performed at least twice, and preparative polymerization experiments were performed three times. Under an N2 atmosphere, a solution of monomer A (cyclobutene derivative) in CD2Cl2 (300 μL) was added to the NMR tube. Then 300 μL of Grubbs III stock solution (C = 0.02 M) was added to the NMR tube. After complete mixing of the solution, NMR spectra were acquired at 25 °C until the catalyst had reacted with monomer A as determined by the disappearance of its α alkylidene proton signal. Monomer B (cyclohexene 6) was added to the NMR tube. After no further propagation occurred, the reaction was quenched with ethyl vinyl ether and stirred for 1 h. Solvent was evaporated, and polymer was purified by chromatography over silica gel (97:3/CH2Cl2:acetone). Yield was determined by assuming 100% conversion of monomer A.

NMR AROMP of 2 and 6

Monomer 2 (8.3 mg, 60 μmol, 10 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed in CD2Cl2. The reaction was followed by 1H NMR spectroscopy at 25 °C for 5 h before the temperature was elevated to 50 °C. Cyclohexene 6 (12 μL, 120 μmol, 20 equiv) was added. No change in the alkylidene peak of the catalyst was observed within 300 min.

NMR AROMP of 3 and 6, Poly(3-alt-6)13

Monomer 3 (23.8 mg, 150 μmol, 25 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed. Cyclohexene 6 (24.5 mg, 30 μL, 50 equiv) was added 30 min later. The NMR tube was spun for 19 h at 25 °C. Flash column chromatography (97:3/CH2Cl2:acetone) of the crude product yielded poly(3-alt-6)13 (15 mg, 43%). 1H NMR (600 MHz, CD2Cl2): δ 7.35–7.14 (m, 5H), 6.60 (m, 13H), 5.32 (m, 27H), 3.68–3.60 (m, 54H), 3.20–3.10 (m, 14H), 2.0–2.3 (m, 10H), 2.60–1.00 (m, 267H).

NMR AROMP of 3 and 6-d10, Poly(3-alt-6-d10)6

Monomer 3 (9.5 mg, 50 μmol, 10 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed. Cyclohexene 6-d10 (9.8 mg, 12 μL, 20 equiv) was added 30 min later. The NMR tube was spun for 8 h at 25 °C. The crude product was purified by flash column chromatography (97:3/CH2Cl2:acetone) to yield poly(3-alt-6-d10)6 (4.8 mg, 40%). 1H NMR (600 MHz, CD2Cl2): δ 7.35–7.14 (m, 5H), 7.02 (dd, J = 8.1, 5.7 Hz, 1H), 5.32 (m, 6H), 3.68–3.60 (m, 22H), 3.20–1.00 (m, 80H).
Alternating ring-opening polymerization of monomer 4 and 6 was carried out at different temperatures ranging from 25 to 60 °C to optimize reaction conditions.

NMR AROMP of 4 and 6, Poly(4-alt-6)16

Monomer 4 (19.9 mg, 120 μmol, 20 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed in CD2Cl2. Cyclohexene 6 (19.7 mg, 24 μL, 40 equiv) was added after 50 min. The NMR tube was spun for 8 h at 25 °C to reach 90% consumption of monomer 4. The crude product was subjected to flash column chromatography (97:3/CH2Cl2:acetone) to yield poly(4-alt-6)16 (16 mg, 53%). 1H NMR (600 MHz, CD2Cl2): δ 7.35–7.14 (m, 5H), 6.52 (m, 16H), 5.79 (m, 15H), 5.31 (m, 26H), 3.69–3.59 (m, 45H), 2.60 (m, 23H), 2.25 (m, 60H), 2.00–1.22 (m, 266H). 13C NMR (100 MHz, CDCl3): δ 169.4, 142.4, 141.9, 136.3, 131.2, 130.7, 130.6, 130.4, 130.2, 130.2, 130.0, 129.1, 128.4, 51.5, 51.5, 51.4, 43.9, 42.8, 37.3, 28.7, 28.1, 21.8, 21.7.

NMR AROMP of 4 and 6, Poly(4-alt-6)16

Monomer 4 (19.9 mg, 120 μmol, 20 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed in CD2Cl2, and cyclohexene 6 (19.7 mg, 24.2 μL, 40 equiv) was added after 50 min. The NMR tube was spun for 6 h at 35 °C to reach >95% consumption of monomer 4. The crude product was subjected to flash column chromatography (97:3/CH2Cl2:acetone) to yield poly(4-alt-6)16 (20 mg, 65%). 1H NMR (600 MHz, CDCl3): δ 7.35–7.14 (m, 6H), 6.52 (m, 16H), 5.79 (m, 15H), 5.50 (m, 1H), 5.31 (m, 17H), 3.69–3.59 (m, 47H), 2.78 (m, 23H), 2.10 (m, 64H), 1.98–1.20 (m, 263H).

NMR AROMP of 4 and 6, Poly(4-alt-6-d10)15

Monomer 4 (19.9 mg, 120 μmol, 20 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed in CD2Cl2. After 50 min, cyclohexene-d106-d10 (19.7 mg, 24.2 μL, 40 equiv) was added. The NMR tube was spun for 6 h at 35 °C to reach >95% consumption of monomer 4. The product was purified by flash column chromatography (97:3/CH2Cl2:acetone) to yield poly(4-alt-6-d10)15 (18 mg, 60%). 1H NMR (600 MHz, CD2Cl2): δ 7.35–7.4 (m, 5H), 5.78 (m, 15H), 5.42 (m, 2H), 3.70–3.60 (m, 45H), 2.82 (m, 23H), 2.25 (m, 27H), 1.78–1.20 (m, 164H).

NMR AROMP of 4 and 6, Poly(4-alt-6)34

Monomer 4 (49.7 mg, 300 μmol, 50 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed in CD2Cl2, and cyclohexene 6 (49.2 mg, 60.6 μL, 100 equiv) was added after 30 min. The NMR tube was spun for 6 h at 35 °C to reach 68% conversion of monomer 4. Partial 1H NMR of crude poly(4-alt-6)34 (600 MHz, CD2Cl2): δ 7.35–7.14 (m, 5H), 6.89 (d, J = 1.2 Hz, 8H), 6.50 (m, 34H), 5.79 (m, 32H), 5.28 (m, 41H), 3.70–3.60 (m, 150H), 3.07–3.04 (m, 10H). (Partial 1H NMR spectroscopic data are reported due to incomplete polymerization and significant upfield overlap of 4 and 6 with the new peaks from the polymer.)

NMR AROMP of 4 and 6, Poly(4-alt-6)36

Monomer 4 (49.7 mg, 300 μmol, 50 equiv) and Grubbs III catalyst (5.3 mg, 6.0 μmol, 1 equiv) were mixed in CD2Cl2. After 30 min, cyclohexene 6 (49.2 mg, 60.6 μL, 100 equiv) was added. The NMR tube was spun for 2 h at 60 °C to reach 72% conversion of monomer 4. The product was purified by flash column chromatography (97:3/CH2Cl2:acetone) to yield poly(4-alt-6)36 (36 mg, 65%). 1H NMR (600 MHz, CD2Cl2): δ 7.35–7.14 (m, 5H), 6.50 (m, 36H), 5.79 (m, 34H), 5.28 (m, 55H), 3.70–3.60 (m, 129H), 2.75 (m, 53H), 2.30–2.10 (m, 142H), 1.95–1.20 (m, 589H).

NMR AROMP of 5 and 6, Poly(5-alt-6)10.

Monomer 5 (54.8 mg, 300 μmol, 50 equiv) and Grubbs III catalyst (5.30 mg, 6.00 μmol, 1 equiv) were mixed in CD2Cl2, and cyclohexene 6 (49.0 mg, 60 μL, 100 equiv) was added after 50 min. The NMR tube was spun for 72 h at 35 °C until no further propagation was observed by 1H NMR spectroscopy. The crude product was subjected to flash column chromatography (97:3/CH2Cl2:acetone) to yield poly(5-alt-6)10 (11 mg, 14%). 1H NMR (600 MHz, CD2Cl2): δ 7.35–7.12 (m, 5H), 6.58 (m, 10H), 5.42 (m, 19H), 5.28 (m, 10H), 3.70–3.60 (m, 36H), 3.10–3.00 (m, 10H), 2.77–1.95 (m, 254H).

General Procedure for Ring-Opening Metathesis

Under an N2 atmosphere, a solution of monomer A (cyclobutene derivative, 1, 3, 4, or 5, [A] = 0.03 M) in CD2Cl2 (300 μL) was added to an NMR tube. Then 300 μL of the stock solution of Grubbs III catalyst (C = 0.03 M) was added to the NMR tube. After complete mixing of the solution, the reaction was closely monitored by 1H NMR or 13C NMR spectroscopy.

Procedure for Alternating Ring-Opening Metathesis (AROM-1, BA Dimer Synthesis)

A solution of monomer A (3 or 4, [A] = 0.03 M) in CD2Cl2 (300 μL, 18.86 μmol) was added to an NMR tube that had been flushed with N2. Then 300 μL of the stock solution of Grubbs III catalyst (C = 0.03 M) was added to the NMR tube. After complete mixing of the solution, the reaction was followed by 1H NMR or 13C NMR spectroscopy until >90% of the catalyst (10–12 h) was consumed as determined by disappearance of the Ru alkylidene proton or carbon resonance of the Grubbs III catalyst at 19.1 or 316.1 ppm. Then cyclohexene 6 was added in 10-fold excess, and the reaction was monitored until the Ru alkylidene proton resonance at 19.0 ppm disappeared. The reaction was terminated with ethyl vinyl ether, and the crude mixture was subjected to silica chromatography (100% CH2Cl2). For the products of the 3−6 AROM-1 experiment, partially purified fractions were characterized by mass spectrometry, 1H NMR, 13C NMR, and HSQC spectroscopy (Supporting Information). Fraction I was a white solid identified as E-stilbene. 1H NMR (850 MHz, CD2Cl2): δ 7.53 (dd, J = 8.1, 0.9 Hz, 2H), 7.36 (t, J = 7.7 Hz, 2H), 7.28–7.23 (m, 2H), 7.13 (s, 1H). 13C NMR (214 MHz, CD2Cl2): δ 137.9, 129.2, 129.1, 128.2, 127.0. ESI (M/Z) [M + H]+ 180.1. Fraction II contained Ph-(3-alt-6)1-Ph as the major component (Supporting Information). Fraction III contained cyc-(3-alt-6)1 as the major component (Supporting Information).

Procedure for Sequential Alternating Ring-Opening Metathesis (AROM-2, BA′BA Tetramer Synthesis)

A solution of monomer A (3 or 4, [A] = 0.03 M) in CD2Cl2 (300 μL, 18.86 μmol) was added to an NMR tube that had been flushed with N2. Then 300 μL of the stock solution of Grubbs III catalyst (C = 0.03 M) was added to the NMR tube. After complete mixing of the solution, the reaction was followed by 1H NMR spectroscopy until >90% of the catalyst (10–12 h) was consumed as determined by disappearance of the Ru alkylidene proton of the Grubbs III catalyst at 19.1 ppm; then cyclohexene 6 was added in 10-fold excess. Generation of [Ru]-B-A was monitored by the appearance of a multiplet resonance at 19.0 ppm. When the formation of [Ru]-B-A was complete as judged by the integrated intensity of the resonance, 1 equiv of monomer A′ was added to form [Ru]-A′-B-A and then [Ru]-B-A′-B-A. The reaction was monitored until the Ru alkylidene proton resonance at 19.0 ppm disappeared or the intensity was constant. Then the reaction was terminated with ethyl vinyl ether.

Results and Discussion

ARTICLE SECTIONS
Jump To

Design and Synthesis of Monomers

We noted that using Grubbs III catalyst for the incorporation of a ring into the propagating chain backbone limits backbiting in the case of the well-investigated norbornene ROMP. (35) Therefore, we decided to examine norbornene ester 2 as a partner for cyclohexene in AROMP. We prepared monomer 2 by a modification of the method of Elsheimer (see Experimental Methods). (32) However, when we subjected monomer 2 to AROMP conditions with cyclohexene 6, we observed no polymerization. Furthermore, when the catalyst was mixed with monomer 2, no ring-opened product was observed at all. We attributed the loss of ROMP activity of monomer 2 to the steric hindrance posed by the combination of the bridging methylene group and the ester.
We next tested bicyclic monomers 3–5, designed for their ring strain and lower steric hindrance around the alkenes (Figure 1). These monomers were prepared by Lewis acid catalyzed [2 + 2] cycloaddition according to Snider’s approach. (34) For practicality, we developed a simplified purification procedure for monomer 4 to remove the isomeric byproduct (see Experimental Methods).

Figure 1

Figure 1. Monomers employed in alternating ring-opening metathesis polymerization.

High Resolution Image
Download MS PowerPoint Slide

Relative Kinetics of Ring-Opening Metathesis (ROM)

First, we undertook kinetic monitoring of the initial ring-opening metathesis (ROM) reactions for each of these monomers by 1H NMR spectroscopy (Figure 2). In each of the experiments, an equimolar amount of monomer A (the bicycloalkene ester) and Grubbs III catalyst was mixed in CD2Cl2. The disappearance of the alkylidene signal of the catalyst at 19.1 ppm was followed by 1H NMR spectroscopy; the signal was integrated relative to the methyl ester signals between 3.8 and 3.5 ppm. Under the conditions of the experiment, 50% of monomer 3 was ring opened in 25 min, whereas 50% of monomer 1 was ring-opened in 40 min. Under the same conditions, monomer 4 underwent 50% ring-opening in 100 min and monomer 5 required 300 min for 50% ring-opening. Thus, upon addition of Grubbs III catalyst, monomer 3 has the fastest ring-opening rate, in accordance with the predicted ring strains. (36-38)

Figure 2

Figure 2. Kinetic monitoring of ring-opening metathesis of monomers 1 and 3–5. Monomer and Grubbs III catalyst were mixed in a 1:1 ratio, [A] = [Grubbs III] = 0.03 M. Percent conversion was determined by 1H NMR spectroscopy and integration of the Ru alkylidene α proton resonance relative to the methyl ester resonances (Supporting Information). t1/2 were obtained from the plot, monomer 1: t1/2 = 40 min, monomer 3: t1/2 = 25 min, monomer 4: t1/2 = 100 min; monomer 5: t1/2 = 300 min. Each experiment was performed at least twice, and data from representative experiments are shown.

High Resolution Image
Download MS PowerPoint Slide

Alternating Copolymers

When subjected to Grubbs III catalyst in the absence of cyclohexene 6, each of the three bicyclic monomers 3, 4, and 5 underwent ring-opening; however, no polymerization could be detected. Thus, we established that these monomers are suitable for the preparation of alternating copolymers because their rates of homopolymerization are zero. All three monomers produced copolymers with cyclohexene 6 in the presence of Grubbs III catalyst. The rates of polymerization varied substantially, and all were slower than the rate of AROMP between cyclobutene ester 1 and cyclohexene 6 as determined by 1H NMR spectroscopy (Table 1). Lengths of polymers were determined by integration of alkene proton peaks (H1, H3, and H4, Figure 3) relative to that of the phenyl end group in the 1H NMR spectrum. Copolymerization of monomer 3 or 5 with 6 yielded much shorter polymers than did that of monomer 4 with 6 under the same conditions (Table 1).

Figure 3

Figure 3. Alternating ring-opening metathesis polymerization (AROMP) of monomers 4 and 6. The region of 1H NMR spectra in which backbone olefinic hydrogen resonances of poly(4-alt-6)n appear is shown. (a) Polymer product prepared from cyclohexene and dissolved in CDCl3. The ratio of H1:H3:H4 is 1:1:1. (b) Polymer product prepared from cyclohexene-d10 and dissolved in CD2Cl2. The ratio of H1:H3:H4 is 0:1:0. poly(4-alt-6-d10)n was dissolved in CD2Cl2 instead of CDCl3 to allow accurate integration of the phenyl resonances.

High Resolution Image
Download MS PowerPoint Slide
Table 1. AROMP Applications of Sterically Hindered Monomers with Cyclohexene
entryAB[A]:[B]:[Ru]temp (°C)time (h)% convaDP[AB]b
11610:20:12539810
22610:20:12530 
33625:50:12519NAc13
436-d1020:40:1256806
54620:40:12589616
64620:40:13589716
746-d1020:40:13588515
84650:100:13586834
94650:100:16027236
105650:100:135248510
a

Percent conversion determined by integration of 1H NMR spectra of monomer A unless specified otherwise.

b

DP[AB] was determined by 1H NMR spectroscopy with integration relative to the phenyl end group and represents the average numbers of AB dyads incorporated in linear copolymers.

c

% conv could not be determined by 1H NMR spectroscopy due to overlap of alkene and polymer peaks.

Furthermore, the 1H NMR spectrum of each of the polymers is consistent with an alternating backbone structure (Supporting Information) in which the olefin bearing a carbomethoxy substituent has an E configuration. For example, in the spectrum of poly(4-alt-6)13, the proton resonance for the carbomethoxy-substituted olefin (H1), which is derived from cyclohexene 6, has an integration identical to that of the H3 alkene resonance at 5.8 ppm which is derived from monomer 4 (Figure 3a). Likewise, the analogous proton resonances in poly(3-alt-6)n and poly(5-alt-6)n have nearly identical integration values. Moreover, characterization of poly(4-alt-6)n by HSQC spectroscopy confirmed that the carbomethoxy-substituted olefin is a single stereoisomer; there is a single H1 signal at 6.5 ppm that correlates with C1 (Supporting Information). Comparison of model compound chemical shifts with the H1 alkene chemical shift further confirmed that the E configuration was obtained. (39, 40)
Further evidence for the alternating structure was obtained for the poly(4-alt-6)n copolymers by experiments with cyclohexene-d10, 6-d10. 1H NMR analysis of the deuterium-labeled copolymer poly(4-alt-6-d10)n indicates a complete loss of the carbomethoxy-substituted olefin (H1) resonance at 6.5 ppm and the H4 alkene resonance at 5.3 ppm (Figure 3b). Complete loss of the H1 and H4 resonances upon deuteration is consistent with a rigorously alternating AB linear scaffold. Their loss indicates the absence of AA dyads that can form upon backbiting during the AROMP. (27) Likewise, in the experiments with deuterated cyclohexene, the integrated ratio of H3 versus the methyl ester remains at 1:3, suggesting that no BB dyad is formed. Therefore, introduction of a cyclohexyl ring fused to the cyclobutene ester monomer provides access to linear, alternating copolymers.
All three monomers 3–5 produced rigorously alternating copolymers. However, at the same concentrations and monomer/catalyst ratios, monomers 3 and 5 both generated shorter polymers than did monomer 4 (Table 1). Monomer 4 provided polymers with up to 35–36 AB repeats. Reaction conditions for poly(4-alt-6)n were examined, and the best yield was obtained in CH2Cl2, at temperatures between 35 and 60 °C. The GPC elution profile of poly(4-alt-6)n displayed a monomodal molecular weight distribution (Supporting Information). This distribution is consistent with the absence of cyclic polymer. Likewise, the dispersity (DM = 2.0 ± 0.1) of poly(4-alt-6)n was significantly smaller than that of the previously reported poly(1-alt-6)n (DM = ∼5), which displayed a bimodal molecular weight distribution. (27) The molecular weight profile is consistent with the absence of intramolecular chain transfer for the AROMP of monomer 4 and cyclohexene.

Intrinsic Rates of Chain Propagation

Monomer 3 was selected for comparison with monomer 4 in order to study how their structures affect the initiation and propagation rates and the extents of polymerization. To preclude the possibility that impurities in monomer 3 inherited from synthesis (see Experimental Methods) deactivated the catalyst, monomer 3 was also treated with m-CPBA and reisolated. This sample was utilized in AROMP and compared with monomer 3 synthesized otherwise. No difference in activity or polymer length was observed.
Then we undertook kinetic monitoring of AROM-1 (formation of BA dimer) with monomers 3 or 4 and cyclohexene 6 by 13C NMR spectroscopy. In both reactions, we observed formation of [Ru]-A upon addition of the A monomer to Grubbs III catalyst (Figure 4, [Ru] + 3 and [Ru] + 4) and disappearance of Ru catalyst. In the case of [Ru]-4, the formation of a single Ru carbene (314.5 ppm) was observed. Addition of cyclohexene cleanly yielded [Ru]-6-4 (338.0 ppm, Figure 4, 6 + [Ru]-4) in 1.5 h, and there was no further change in the NMR spectrum over 30 h.

Figure 4

Figure 4. Alternating ring-opening metathesis (AROM-1) of monomers 3 and 6 and monomers 4 and 6. The carbene regions of 13C NMR spectra of (3-alt-6)1 (left) and (4-alt-6)1 (right) are shown. In the top spectra, [Ru] catalyst was mixed with 3 or 4 in CD2Cl2 for 10–12 h. Cyclohexene was added after >90% of Ru catalyst was consumed. The 6 + [Ru]-3 reaction was monitored for 300 min, and 6 + [Ru]-4 reaction was monitored for 30 h. The 13C NMR spectrum of 6 + [Ru]-3 was acquired 30–50 min after addition of cyclohexene, and the 13C NMR spectrum of 6 + [Ru]-4 was acquired 50–70 min after addition of cyclohexene. Each experiment was performed at least twice, and data from representative experiments are shown.

High Resolution Image
Download MS PowerPoint Slide
In the case of [Ru]-3, two Ru carbene species were produced (311.5 and 311.8 ppm). After the addition of cyclohexene, we observed regeneration of the Grubbs III catalyst (316.1 ppm) in addition to the [Ru]-6-3 carbene (337.8 ppm, Figure 4, 6 + [Ru]-3) during the first 2 h of reaction. Within 5 h of cyclohexene addition, both the [Ru]-6-3 and Ru catalyst carbene resonances disappeared, and no new carbene resonances appeared.
We analyzed products of the AROM-1 reaction and obtained Ph-(3-alt-6)1-Ph, E-stilbene, and cyc-(3-alt-6)1 (Scheme 1a). Hence, backbiting or cross-metathesis can occur very early in the reaction. An independent experiment in which Ru catalyst was mixed with monomer 3 for 18 h showed that [Ru]-3 remains intact. Thus, the Ru enoic carbene is not reactive with itself, and side reactions must occur after cyclohexene addition. Formation of stilbene suggests that if the desired propagation pathway is kinetically less favorable, the Ru alkylidene ([Ru]-6-3) species undergoes cross-metathesis in an intra- or intermolecular reaction with the styrene end group. In contrast, no regeneration of Grubbs III catalyst was observed in the (4-alt-6)1 experiment (Figure 4, 6 + [Ru]-4). The [Ru]-6-4 carbene remained stable for 2 days under the reaction conditions. This result is consistent with our observations that monomer 4 provides a longer and backbiting-free linear alternating copolymer via AROMP.

Scheme 1

Scheme 1. (a) Alternating Ring-Opening Metathesis (AROM-1) of 3 or 4 with Cyclohexene To Form BA Dimer and Proposed Intra- and Intermolecular Cross-Metathesis for (3-alt-6)1;a (b) Double Alternating Ring-Opening Metathesis (AROM-2) To Form BA′BA Tetramerb
High Resolution Image
Download MS PowerPoint Slide

Scheme aCarbenes (circled) were monitored by 13C NMR spectroscopy (Figure 4).

Scheme bThe proton resonances monitored are colored red (Figure 5).

We also carried out double AROM (AROM-2) experiments with monomers 3 and 4 to compare their behavior in systems with longer chains (Scheme 1 and Figure 5). In these experiments, we mixed monomer A and catalyst in a 1:1 ratio in an NMR tube to form [Ru]-A, and we monitored the reactions by 1H NMR spectroscopy. The mixtures were allowed to react for 10–12 h to ensure nearly complete conversion to [Ru]-A (the benzylidene proton signal at 19.1 ppm was reduced to less than 10% of its original intensity). At this time, 10 equiv of cyclohexene (monomer B) was added to generate [Ru]-B-A (Figure 5). The formation of [Ru]-B-A was monitored by the appearance of a new multiplet resonance at 19.0 ppm corresponding to the alkylidene proton (Supporting Information). We found that cyclohexene 6 reacts with ring-opened monomer 3 enoic carbene 1.5 times faster (t1/2 = 28 ± 1 min) than with the corresponding enoic carbene from monomer 4 (t1/2 = 43 ± 5 min) (Figure 5 and Supporting Information). When the formation of Ru alkylidene ([Ru]-B-A) was complete as judged by integration of the resonance at 19.0 ppm, 1 equiv of monomer A′ was added to investigate the rate of ring-opening catalyzed by [Ru]-B-A. We examined all four cases of double ROM: ROM of 3 with [Ru]-6-3 and with [Ru]-6-4 and ROM of 4 with [Ru]-6-4 and with [Ru]-6-3. The disappearance of the monomer A′ alkene signal at 6.7 ppm and that of the [Ru]-B-A alkylidene signal at 19.0 ppm were monitored as a function of time. Both signals disappeared at the same rate as measured by comparison of the integrals with that of the signal for ester peaks. We found that reaction of monomer 3 with [Ru]-6-4 (t1/2 = 26 ± 1 min) was 27% faster than its reaction with [Ru]-6-3 (t1/2 = 33 ± 1 min). In the case of the reaction of monomer 4 with [Ru]-6-A, the rate with [Ru]-6-4 (t1/2 = 41 ± 4 min) is 17% faster than the rate with [Ru]-6-3 (t1/2 = 48 ± 2 min). Moreover, oligomers derived from monomer 3 as either A or A′ failed to completely convert to [Ru]-6-A′-6-A; this result is consistent with the premise that competing cross-metathesis reactions dominate the reaction (Figure 5).

Figure 5

Figure 5. Kinetic monitoring of double ring-opening metathesis (AROM-2) reactions of monomer A (3 or 4) with [Ru]-6-A (Scheme 1b). Time zero corresponds to the addition of 1 equiv of monomer A′ (3 or 4) to 1 equiv of [Ru]-6-A in the presence of excess cyclohexene 6. Mole fraction of Ru alkylidene at 19.0 ppm was determined by integration of the Ru alkylidene resonance relative to the methyl ester resonances between 3.5 and 3.8 ppm. The mole percent of [Ru]-6-A at time zero was only 30–42% due to the low concentrations, and thus, the extended reaction times used in the initial AROM to generate [Ru]-6-A. Each experiment was performed at least twice, and data from representative experiments are shown.

High Resolution Image
Download MS PowerPoint Slide
Although the rates of the second ROM did not vary widely, the ROM reaction appears to be very sensitive to long-range polymer structure, i.e., the presence of a five-membered ring in the backbone one position removed from the living [Ru] species reduces the reaction rate of either bicyclic monomer with the unhindered [Ru]-alkylidene. The rates of reaction indicate that the backbone containing a six-membered ring (derived from [4.2.0] monomer) is superior to the backbone containing a five-membered ring (derived from [3.2.0] monomer) for propagation.
We ascribe the differences in reactivity between oligomers derived from monomer 3 versus monomer 4 to the differences in dihedral angles between the cis-1,2 substituents of cyclopentane versus those of cyclohexane (20°–40°, depending on the conformation, and 60°, respectively). (41-48) These dihedral angles determine the relative orientation of the two polymer chain ends as the backbone extends from the cyclic moiety. The orientation of the chain ends determines access to the [Ru]-alkylidene. If the chain ends are aligned, intramolecular cross-metathesis will ensue, as is the case for AROMP of monomers 3 and 6. If access of the incoming monomer to [Ru]-alkylidene is hindered, the rate of propagation will be suppressed and the polymerization reaction is unable to compete with cross-metathesis. Thus, despite the higher strain and inherent reactivity of monomer 3, the resulting polymer backbone appears to hinder propagation and to favor cross-metathesis; both effects lead to the premature termination of polymerization.

Conclusions

ARTICLE SECTIONS
Jump To
We have demonstrated that alternating copolymers are synthetically accessible via AROMP with bicyclic carbomethoxy olefin monomers 3–5 and cyclohexene. These AROMP-active monomers do not self-metathesize regardless of monomer feed ratios or concentrations. Thus, formation of homopolymeric blocks, as is observed in some other systems, (20, 21, 26, 49, 50) does not occur in the 3–5/6 AROMP systems. Ruthenium-catalyzed ring-opening metathesis of cyclohexene and methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate, 4, provides rigorously linear and alternating copolymers free of backbiting and chain transfer. The resulting polymer backbone constrained by a cis-1,2-substituted cyclohexane provides an exciting alternative to traditional norbornyl-derived polymers for the preparation of functional alternating copolymers.

Supporting Information

ARTICLE SECTIONS
Jump To

Figures showing characterization of monomers and polymer, GPC, 1D- and 2D-NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org.

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

ARTICLE SECTIONS
Jump To
  • Corresponding Authors
    • Kathlyn A. Parker - Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States;  Email: [email protected]
    • Nicole S. Sampson - Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States;  Email: [email protected]
  • Author
    • Li Tan - Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
  • Notes
    The authors declare the following competing financial interest(s): We have no competing interests except for National Institutes of Health Funding: R01GM097971 & R01GM74776.

Acknowledgment

ARTICLE SECTIONS
Jump To

We thank the National Institutes of Health (NIH) for grants R01GM097971/R01HD38519 (N.S.S.) and R01GM74776 (K.A.P). We also thank Dr. Francis Picart and James Marecek for their assistance with NMR spectroscopy.

References

ARTICLE SECTIONS
Jump To

This article references 50 other publications.

  1. 1
    Siegwart, D. J.; Oh, J. K.; Matyjaszewski, K. Prog. Polym. Sci. 2012, 37, 18
    [Crossref], [PubMed], [CAS], Google Scholar
    1
    ATRP in the design of functional materials for biomedical applications
    Siegwart, Daniel J.; Oh, Jung Kwon; Matyjaszewski, Krzysztof
    Progress in Polymer Science (2012), 37 (1), 18-37CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Ltd.)
    A review. Atom Transfer Radical Polymn. (ATRP) is an effective technique for the design and prepn. of multifunctional, nanostructured materials for a variety of applications in biol. and medicine. ATRP enables precise control over macromol. structure, order, and functionality, which are important considerations for emerging biomedical designs. This article reviews recent advances in the prepn. of polymer-based nanomaterials using ATRP, including polymer bioconjugates, block copolymer-based drug delivery systems, cross-linked microgels/nanogels, diagnostic and imaging platforms, tissue engineering hydrogels, and degradable polymers. It is envisioned that precise engineering at the mol. level will translate to tailored macroscopic phys. properties, thus enabling control of the key elements for realized biomedical applications.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVaqt7%252FM&md5=b82732d7335993e45d7642a0855cb7af
  2. 2
    Jeong, B.; Bae, Y. H.; Lee, D. S.; Kim, S. W. Nature 1997, 388, 860
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  3. 3
    Cölfen, H. Macromol. Rapid Commun. 2001, 22, 219
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  4. 4
    Schacher, F. H.; Rupar, P. A.; Manners, I. Angew. Chem., Int. Ed. 2012, 51, 7898
    [Crossref], [CAS], Google Scholar
    4
    Functional Block Copolymers: Nanostructured Materials with Emerging Applications
    Schacher, Felix H.; Rupar, Paul A.; Manners, Ian
    Angewandte Chemie, International Edition (2012), 51 (32), 7898-7921CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Recent advances in polymer synthesis have significantly enhanced the ability to rationally design block copolymers with tailored functionality. The self-assembly of these macromols. in the solid state or in soln. allows the formation of nanostructured materials with a variety of properties and potential functions. This Review illustrates recent progress in the field of block copolymer materials by highlighting selected emerging applications.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVGgtrbF&md5=f8f2f0c24ac928d2f89f091a18db442e
  5. 5
    Furuta, P. T.; Deng, L.; Garon, S.; Thompson, M. E.; Frechet, J. M. J. Am. Chem. Soc. 2004, 126, 15388
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  6. 6
    Furuta, P.; Brooks, J.; Thompson, M. E.; Fréchet, J. M. J. J. Am. Chem. Soc. 2003, 125, 13165
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  7. 7
    Kim, H. K.; Baek, N. S.; Paik, K. L.; Lee, Y.; Lee, J. H. In Chromogenic Phenomena in Polymers; American Chemical Society: Washington, DC, 2004; Vol. 888, p 247.
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  8. 8
    ten Brummelhuis, N.; Weck, M. ACS Macro Lett. 2012, 1, 1216
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    8
    Orthogonal Multifunctionalization of Random and Alternating Copolymers
    ten Brummelhuis, Niels; Weck, Marcus
    ACS Macro Letters (2012), 1 (10), 1216-1218CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
    A series of copolymers with varying degrees of alternation are synthesized by free-radical polymn. from 2,3,4,5,6-pentafluorostyrene (PFS) and propargyl-contg. styrene derivs. The degree of alternation varied with the electronic nature of the styrene deriv.: random copolymers were obtained using monomers with electron withdrawing moieties, whereas increasingly alternating copolymers were obtained by increasing the electron donating nature of the substituent. The copolymers could be functionalized in an orthogonal fashion using a nucleophilic substitution (with thiols) to functionalize PFS and the copper-catalyzed 3 + 2 cycloaddn. between azides and the alkyne of the propargyl groups. This methodol. allows for the facile synthesis of functional alternating copolymers.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVGisLjP&md5=9e297fd69a0fcd80e78fdb227a6caad7
  9. 9
    Romulus, J.; Tan, L.; Weck, M.; Sampson, N. S. ACS Macro Lett. 2013, 2, 749
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    9
    Alternating Ring-Opening Metathesis Polymerization Copolymers Containing Charge-Transfer Units
    Romulus, Joy; Tan, Li; Weck, Marcus; Sampson, Nicole S.
    ACS Macro Letters (2013), 2 (8), 749-752CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
    Alternating copolymers derived from the ring-opening metathesis polymn. (ROMP) of functionalized cyclobutene esters (CBEs) and cyclohexenes were described. The copolymer poly(CBE-alt-CH)n contains alternating side chains based on dialkoxynaphthalene and pyromellitic dianhydride. Characterization by UV-vis spectroscopy showed that the copolymers exhibit an increase in charge-transfer intensity in comparison to previously reported alternating copolymers. The bulky side chains inhibit backbiting during the polymn. and allow for enhanced control over the polymn. in comparison to copolymers functionalized with linear alkyl groups.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXht1WisrvL&md5=5ef262306acc65e1de63e9950428b4d9
  10. 10
    Lutz, J.-F.; Kirci, B.; Matyjaszewski, K. Macromolecules 2003, 36, 3136
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    10
    Synthesis of well-defined alternating copolymers by controlled/living radical polymerization in the presence of Lewis acids
    Lutz, Jean-Francois; Kirci, Betul; Matyjaszewski, Krzysztof
    Macromolecules (2003), 36 (9), 3136-3145CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Several controlled/living radical polymn. (CRP) techniques (atom transfer radical polymn. (ATRP), nitroxide-mediated polymn. (NMP), iodide degenerative transfer polymn. (IDTP), and reversible addn.-fragmentation transfer polymn. (RAFT)) were studied for the alternating copolymn. of a donor monomer (styrene) and an acceptor monomer (Me methacrylate or Me acrylate) complexed with Lewis acid. RAFT polymn. was found to be the most versatile system. The combination of RAFT and Lewis acids complexation techniques allows synthesis of well-defined alternating copolymers poly(styrene-alt-Me methacrylate) with controlled mol. wt. (up to Mn = 70 000 g mol-1), low polydispersities (Mw/Mn < 1.3), and controlled comonomer sequences (∼90% of alternating triads). These results were obtained in the presence of diethylaluminum chloride and ethylaluminum sesquichloride. Moreover, the alternating copolymers obtained in such copolymns. retain chain end functionality and were used as macroinitiators for the synthesis of well-defined diblock copolymers poly(Me methacrylate-alt-styrene)-b-polystyrene.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXis1Ohur8%253D&md5=271ae41fbae52783d72b8c4d362e43e8
  11. 11
    Chen, G.-Q.; Wu, Z.-Q.; Wu, J.-R.; Li, Z.-C.; Li, F.-M. Macromolecules 1999, 33, 232
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  12. 12
    Shirota, Y.; Yoshimura, M.; Matsumoto, A.; Mikawa, H. Macromolecules 1974, 7, 4
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  13. 13
    Kamigaito, M.; Ando, T.; Sawamoto, M. Chem. Rev. 2001, 101, 3689
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    13
    Metal-Catalyzed Living Radical Polymerization
    Kamigaito, Masami; Ando, Tsuyoshi; Sawamoto, Mitsuo
    Chemical Reviews (Washington, D. C.) (2001), 101 (12), 3689-3745CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review on the discovery and the subsequent fast development of living radical polymns. catalyzed by transition metal complexes in the period from 1994 to early 2001.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXovFagtrg%253D&md5=f3637af46a7c4fb5734f4211c8671dd7
  14. 14
    Moad, G.; Rizzardo, E.; Thang, S. H. Aust. J. Chem. 2012, 65, 985
    [Crossref], [CAS], Google Scholar
    14
    Living Radical Polymerization by the RAFT Process - A Third Update
    Moad, Graeme; Rizzardo, Ezio; Thang, San H.
    Australian Journal of Chemistry (2012), 65 (8), 985-1076CODEN: AJCHAS; ISSN:0004-9425. (CSIRO Publishing)
    A review. This paper provides a third update to the review of reversible deactivation radical polymn. (RDRP) achieved with thiocarbonylthio compds. (ZC(=S)SR) by a mechanism of reversible addn.-fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379). The first update was published in Nov. 2006 (Aust. J. Chem. 2006, 59, 669) and the second in Dec. 2009 (Aust. J. Chem. 2009, 62, 1402). This review cites over 700 publications that appeared during the period mid 2009 to early 2012 covering various aspects of RAFT polymn. which include reagent synthesis and properties, kinetics and mechanism of polymn., novel polymer syntheses, and a diverse range of applications. This period has witnessed further significant developments, particularly in the areas of novel RAFT agents, techniques for end-group transformation, the prodn. of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlWmu7%252FE&md5=ffb85869b82366af7db21722417128a8
  15. 15
    Ouchi, M.; Terashima, T.; Sawamoto, M. Chem. Rev. 2009, 109, 4963
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    15
    Transition Metal-Catalyzed Living Radical Polymerization: Toward Perfection in Catalysis and Precision Polymer Synthesis
    Ouchi, Makoto; Terashima, Takaya; Sawamoto, Mitsuo
    Chemical Reviews (Washington, DC, United States) (2009), 109 (11), 4963-5050CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. The review covers two chronol. periods: 1. 1994-2000 (460 refs.), 2 2001-2008 (970 refs.). The two periods were compared and major discoveries were summarized.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtF2ltbfK&md5=bbca8bbf872f6870f5a48d1d99cdde14
  16. 16
    Al Samak, B.; Carbill, A. G.; Hamilton, J. G.; Rooney, J. J.; Thompson, J. M. Chem. Commun. 1997, 2057
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  17. 17
    Amir-Ebrahimi, V.; Corry, D. A.; Hamilton, J. G.; Thompson, J. M.; Rooney, J. J. Macromolecules 2000, 33, 717
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  18. 18
    Amir-Ebrahimi, V.; Rooney, J. J. J. Mol. Catal. A: Chem. 2004, 208, 115
    [Crossref], [CAS], Google Scholar
    18
    Remarkable alternating effect in metathesis copolymerization of norbornene and cyclopentene using modified Grubbs ruthenium initiators
    Amir-Ebrahimi, Valia; Rooney, John J.
    Journal of Molecular Catalysis A: Chemical (2004), 208 (1-2), 115-121CODEN: JMCCF2; ISSN:1381-1169. (Elsevier Science B.V.)
    High trans and mainly cis directing Grubbs Ru initiators, I, II, III, and IV, resp. were investigated as catalysts for metathesis copolymn. of norbornene and cyclopentene. When the Lewis acid, MoCl5 or WCl6, is added to these Lewis bases initiators, I-III, a cage effect develops such that the polymers become alternating caused by the severe or almost total denial of access of norbornene to the propagating metallacarbenes. Addn. of ethers destroys the cages and removes the effect. In marked contrast the N-heterocyclic ligand Grubbs initiator, IV, does not show the effect, as addn. of MoCl5 only seems to retard the overall reaction, but does not change the copolymer compn.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXpvVWrur8%253D&md5=81a72598fa7a65661f0fae88759d4cb2
  19. 19
    Torker, S.; Müller, A.; Chen, P. Angew. Chem. 2010, 122, 3850
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  20. 20
    Bornand, M.; Torker, S.; Chen, P. Organometallics 2007, 26, 3585
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    20
    Mechanistically Designed Dual-Site Catalysts for the Alternating ROMP of Norbornene and Cyclooctene
    Bornand, Marc; Torker, Sebastian; Chen, Peter
    Organometallics (2007), 26 (14), 3585-3596CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    Mechanistic work on the olefin metathesis reaction by well-characterized ruthenium carbene complexes led to the rational design and synthesis of a modified, unsym. "first-generation" catalyst, which, in contrast to either first- or second-generation systems with sym. ligands, converts a mixt. of two cycloolefin monomers to a largely alternating copolymer. The mechanistic concept of a homogeneous catalyst that switches between more than one state at each turnover is general. The structures of the complexes, detd. by mass spectrometry, NMR, and x-ray crystallog., reveal some unexpected features, which explain sequence errors in the copolymer.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXmt1arsL4%253D&md5=15ad1e22ce39e9af70f3f48d3661792f
  21. 21
    Bornand, M.; Chen, P. Angew. Chem., Int. Ed. 2005, 44, 7909
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  22. 22
    Torker, S.; Müller, A.; Sigrist, R.; Chen, P. Organometallics 2010, 29, 2735
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  23. 23
    Vehlow, K.; Lichtenheldt, M.; Wang, D.; Blechert, S.; Buchmeiser, M. R. Macromol. Symp. 2010, 296, 44
    [Crossref], [CAS], Google Scholar
    23
    Alternating Ring-Opening Metathesis Copolymerization of Norborn-2-ene with cis-Cyclooctene and Cyclopentene
    Vehlow, Kati; Lichtenheldt, Martin; Wang, Dong-Ren; Blechert, Siegfried; Buchmeiser, Michael R.
    Macromolecular Symposia (2010), 296 (Modern Trends in Polymer Science--EPF'09), 44-48CODEN: MSYMEC; ISSN:1022-1360. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Ru-alkylidenes based on unsym. imidazolin-2-ylidenes, were used for the alternating copolymn. of norborn-2-ene (NBE) with cis-cyclooctene (COE) and cyclopentene (CPE), resp. Alternating copolymers, i.e., poly(NBE-alt-COE)n and poly(NBE-alt-CPE)n contg. up to 97 and 91% alternating diads, resp., were obtained. The copolymn. parameters of the alternating copolymn. of NBE with CPE under the action of different initiators were detd. using a first order Markov model. Hydrogenation of poly(NBE-alt-COE)n yielded a fully satd., hydrocarbon-based polymer.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsFSgtrnJ&md5=42a00dff9a615500d5a36845d47f0550
  24. 24
    Vehlow, K.; Wang, D.; Buchmeiser, M. R.; Blechert, S. Angew. Chem., Int. Ed. 2008, 47, 2615
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  25. 25
    Buchmeiser, M. R.; Ahmad, I.; Gurram, V.; Kumar, P. S. Macromolecules 2011, 44, 4098
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  26. 26
    Ilker, M. F.; Coughlin, E. B. Macromolecules 2001, 35, 54
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  27. 27
    Song, A.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2009, 131, 3444
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  28. 28
    Sutthasupa, S.; Shiotsuki, M.; Masuda, T.; Sanda, F. J. Am. Chem. Soc. 2009, 131, 10546
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  29. 29
    Choi, T.-L.; Lee, C. W.; Chatterjee, A. K.; Grubbs, R. H. J. Am. Chem. Soc. 2001, 123, 10417
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  30. 30
    Song, A.; Parker, K. A.; Sampson, N. S. Org. Lett. 2010, 12, 3729
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  31. 31
    Love, J. A.; Morgan, J. P.; Trnka, T. M.; Grubbs, R. H. Angew. Chem., Int. Ed. 2002, 41, 4035
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  32. 32
    Elsheimer, S.; Slattery, D. K.; Michael, M.; Weeks, J.; Topoleski, K. J. Org. Chem. 1989, 54, 3992
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  33. 33
    Mathias, L. J. Synthesis (Stuttgart) 1979, 561
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  34. 34
    Snider, B. B.; Rodini, D. J.; Cionn, R. S. E.; Sealfon, S. J. Am. Chem. Soc. 1979, 101, 5283
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  35. 35
    Choi, T.-L.; Grubbs, R. H. Angew. Chem., Int. Ed. 2003, 42, 1743
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  36. 36
    Baird, N. C. Tetrahedron 1970, 26, 2185
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Schleyer, P. R.; Williams, J. E.; Blanchard, K. R. J. Am. Chem. Soc. 1970, 92, 2377
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    37
    Evaluation of strain in hydrocarbons. The strain in adamantane and its origin
    Schleyer, Paul von R.; Williams, James Earl, Jr.; Blanchard, K. R.
    Journal of the American Chemical Society (1970), 92 (8), 2377-86CODEN: JACSAT; ISSN:0002-7863.
    Many group-increment and bond-energy additivity schemes, e.g., the frequently employed one by Franklin, devised for calcn. of heats of formation of acyclic alkanes, are inadequate for cyclic systems. Even those schemes which treat cyclic mols. well are not applicable to defining hydrocarbon strain energies. Group increments, derived from the heats of formation of the acyclic alkanes in completely skew-free conformations, are: Me, -10.05; CH2, -5.13; CH, -2.16; C, -0.30 kcal. These "single-conformation" increments are recommended for the evaluation of strain in hydrocarbons and tables of such strain estimates are provided. A modest strain in cyclochexane (1.35 kcal/mole) and trans-Decalin (1.79 kcal/mole) is indicated. More surprising is the finding of 6.48 kcal/mole of strain in adamantane, thought previously to be a "strain-free" mol. This strain can be accounted for quant. in terms of angle strain and C...C nonbonded repulsions from which the rigidity of adamantane skeleton allows no escape, provided rather hard C...C nonbonded potential functions are employed in computer conformational anal. calcns. Softer C...C nonbonded functions are less satisfactory, as they do not reproduce well the energies and geomteries of bridged hydrocarbons. Special cage effects need not be invoked in interpreting the strain in adamantane, nor, presumably, in other bridged polycyclic mols.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3cXhtlWrtLs%253D&md5=a7b06cfb246e1c3820dda844428b16c4
  38. 38
    Wiberg, K. B. Angew. Chem., Int. Ed. 2003, 25, 312
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  39. 39
    Lee, J. C.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2006, 128, 4578
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  40. 40
    Beak, P.; Kempf, D. J.; Wilson, K. D. J. Am. Chem. Soc. 1985, 107, 4745
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  41. 41
    Allinger, N. L.; Tribble, M. T.; Miller, M. A.; Wertz, D. H. J. Am. Chem. Soc. 1971, 93, 1637
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  42. 42
    Hoyland, J. R. J. Chem. Phys. 1969, 50, 2775
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  43. 43
    Allinger, N. L.; Hirsch, J. A.; Miller, M. A.; Tyminski, I. J.; Van Catledge, F. A. J. Am. Chem. Soc. 1968, 90, 1199
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  44. 44
    Fuchs, B. In Topics in Stereochemistry; Eliel, E. L.; Wilen, S. H.; Allinger, N. L., Eds.; Interscience: 1978; Vol. 10, p 1.
    Google Scholar
    There is no corresponding record for this reference.
  45. 45
    Wilson, N. K.; Stochters, J. B.; Bucourt, R.; Kellie, G. M.; Friddell, F. G.; Moriarty, R. M. In Topics in Stereochemsitry; Eliel, E. L.; Wilen, S. H.; Allinger, N. L., Eds.; Interscience: New York, 1974; Vol. 8, p 1.
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  46. 46
    Testa, B.; Vistoli, G.; Pedretti, A. Helv. Chim. Acta 2013, 96, 564
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  47. 47
    Abraham, R. J.; Koniotou, R.; Sancassan, F. J. Chem. Soc., Perkin Trans. 2 2002, 2025
    [Crossref], [CAS], Google Scholar
    47
    Conformational analysis.Part 39. A theoretical and lanthanide induced shift (LIS) investigation of the conformations of cyclopentanol and cis- and trans-cyclopentane-1,2-diol
    Abraham, Raymond J.; Koniotou, Rodothea; Sancassan, Fernando
    Journal of the Chemical Society, Perkin Transactions 2 (2002), (12), 2025-2030CODEN: JCSPGI; ISSN:1472-779X. (Royal Society of Chemistry)
    The conformations of cyclopentanol and cis- and trans-cyclopentane-1,2-diol have been studied by ab initio and mol. mechanics (MM) calcns. and by the LIS technique, using Yb(fod)3 to obtain the induced shifts of all 1H and 13C nuclei in the mol., together with complexation shifts obtained by the use of La(fod)3. The MM calcns. gave two optimized geometries for cyclopentanol. These were envelope conformations with the hydroxyl group equatorial (1A) and axial (1B) at the flap of the envelope. In contrast Gaussian 98 at the B3LYP level with the 6-31G** basis set gave an optimized geometry (1C) which was an envelope conformation with the hydroxyl group in an axial position at the fold of the envelope. ΔE(1A - 1B) = 0.47 kcal mol-1 (MM) and 0.93 kcal mol-1 (ab initio) and ΔE (1B - 1C) = 0.15 kcal mol-1 (ab initio). The MM and ab initio calcns. for cis-1,2-cyclopentanediol gave different envelope conformations (2A) and (2B), both with one equatorial and one axial hydroxyl group. For trans-1,2-cyclopentanediol both calcns. gave the same geometries, an envelope conformation with two axial hydroxyls (3A) and a half chair conformer with diequatorial hydroxyls (3B). ΔE (3A - 3B) = 2.9 kcal mol-1 ( MM) and 0.70 kcal mol-1 (ab initio). The LIRAS4 model involving an sp3 hybridized oxygen atom with two sym. lone pairs was used for these compds. The calcd. LIS for cyclopentanol gave poor agreement with the obsd. data for 1A, moderate agreement for 1B but good agreement for 1C. A LIS anal. combining 1B and 1C suggests that the population of 1C was >80% in CHCl3 soln. The ab initio calcns. and the LIS anal. agree that the unsym. conformer 1C is the major form in soln. The similarity between this conformer of cyclopentanol and that of the furanose sugars suggests that the anomeric effect may be more fundamental than hitherto realized. In cis-cyclopentane-1,2-diol the obsd. data were in good agreement with the calcd. LIS for both 2A and 2B. In trans-cyclopentane-1,2-diol the obsd. data were in good agreement with the calcd. LIS for 3B but in poor agreement for 3A. The LIS allowed the assignment of the proton chem. shifts of the individual methylene protons in these mols. which had not been given previously.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38Xpt1ylsro%253D&md5=7985561855b8eb966e103633b41ee323
  48. 48
    Abraham, R. J.; Koniotou, R. Magn. Reson. Chem. 2003, 41, 1000
    [Crossref], [CAS], Google Scholar
    48
    Conformational analysis. Part 40:+ A theoretical and NMR investigation of the conformations of cis- and trans-cyclopentane-1,3-diol
    Abraham, Raymond J.; Koniotou, Rodothea
    Magnetic Resonance in Chemistry (2003), 41 (12), 1000-1008CODEN: MRCHEG; ISSN:0749-1581. (John Wiley & Sons Ltd.)
    The conformations of cis- (1) and trans-cyclopentane-1,3-diol (2) have been studied by ab initio (Gaussian 98) and mol. mechanics (PCMODEL) calcns. and by NMR spectroscopy. The calcns. gave two low-energy conformations for (1), 1A and 1B, both with axial hydroxyl groups. Two conformations with equatorial hydroxyl groups (1C and 1D) were found but with much higher energy (ca 4.0 kcal mol-1). Five low-energy conformers were found for 2. Four were envelope conformations and one a half-chair. The complete anal. of the 400 MHz 1H NMR spectra of 1 in a variety of solvents and 2 in chloroform was performed by extensive decoupling expts., iterative computer anal. and spectral simulation. This gave all the H,H couplings in the mol., including in 1 a long-range 4J(H,H) coupling between H-2cis and H-4,5cis. The 3J(H,H) couplings were used to det. the conformer populations in these mols. This was initially achieved using the Haasnoot, de Leeuw and Altona equation, to obtain the conformer couplings. It was found that this equation was not accurate for the C·CH2·CH2·C fragment in these mols. and the following equation was derived for this fragment from five- and six- membered cyclic compds. in fixed conformations:. 3J(H,H) = 11.16 cos2.vphi. - 1.28 cos.vphi. + 0.77. The conformer populations were obtained by calcg. the conformer couplings which were then compared with the obsd. couplings. Compd. 1 in benzene soln. is an approx. equal mixt. of conformers 1A and 1B with small (<4%) amts. of 1C and 1D. In the polar solvents acetone and acetonitrile the populations of 1A and 1B are again equal, with 20% of 1C and <2% of 1D. In 2 the major conformers are 2B and 2D with small amts. of 2C, 2E and 2A. These novel findings are considered with previous data on cyclopentanol and cis- and trans-cyclopentane-1,2-diol and it is shown that the axial hydroxyl substituent at the fold of the envelope appears to be a major factor in detg. the conformational energies of these compds.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXpsV2ms7Y%253D&md5=bc8b82b591187411eefb8b834497823f
  49. 49
    Choi, T.-L.; Rutenberg, I. M.; Grubbs, R. H. Angew. Chem., Int. Ed. 2002, 41, 3839
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  50. 50
    Romulus, J.; Patel, S.; Weck, M. Macromolecules 2011, 45, 70
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.

Cited By

This article is cited by 32 publications.

  1. Francis O. Boadi, Nicole S. Sampson. Long-Range Kinetic Effects on the Alternating Ring Opening Metathesis of Bicyclo[4.2.0]oct-6-ene-7-carboxamides and Cyclohexene. ACS Organic & Inorganic Au 2023, Article ASAP.
  2. Kaoru Tashiro, Midori Akiyama, Kimiaki Kashiwagi, Takashi Okazoe. The Fluorocarbene Exploit: Enforcing Alternation in Ring-Opening Metathesis Polymerization. Journal of the American Chemical Society 2023, 145 (5) , 2941-2950. https://doi.org/10.1021/jacs.2c11373
  3. Xuelin Sui, Will R. Gutekunst. Cascade Alternating Metathesis Cyclopolymerization of Diynes and Dihydrofuran. ACS Macro Letters 2022, 11 (5) , 630-635. https://doi.org/10.1021/acsmacrolett.2c00140
  4. Changxia Shi, Ryan W. Clarke, Michael L. McGraw, Eugene Y.-X. Chen. Closing the “One Monomer–Two Polymers–One Monomer” Loop via Orthogonal (De)polymerization of a Lactone/Olefin Hybrid. Journal of the American Chemical Society 2022, 144 (5) , 2264-2275. https://doi.org/10.1021/jacs.1c12278
  5. Gyusaang Youn, Nicole S. Sampson. Substituent Effects Provide Access to Tetrasubstituted Ring-Opening Olefin Metathesis of Bicyclo[4.2.0]oct-6-enes. ACS Organic & Inorganic Au 2021, 1 (1) , 29-36. https://doi.org/10.1021/acsorginorgau.1c00016
  6. Mohammad Yasir, Andreas F. M. Kilbinger. Cascade Ring-Opening/Ring-Closing Metathesis Polymerization of a Monomer Containing a Norbornene and a Cyclohexene Ring. ACS Macro Letters 2021, 10 (2) , 210-214. https://doi.org/10.1021/acsmacrolett.0c00882
  7. Xuelin Sui, Tianqi Zhang, Alec B. Pabarue, Liangbing Fu, Will R. Gutekunst. Alternating Cascade Metathesis Polymerization of Enynes and Cyclic Enol Ethers with Active Ruthenium Fischer Carbenes. Journal of the American Chemical Society 2020, 142 (30) , 12942-12947. https://doi.org/10.1021/jacs.0c06045
  8. Benjamin R. Elling, Jessica K. Su, Yan Xia. Degradable Polyacetals/Ketals from Alternating Ring-Opening Metathesis Polymerization. ACS Macro Letters 2020, 9 (2) , 180-184. https://doi.org/10.1021/acsmacrolett.9b00936
  9. Dylan J. Walsh, Michael G. Hyatt, Susannah A. Miller, Damien Guironnet. Recent Trends in Catalytic Polymerizations. ACS Catalysis 2019, 9 (12) , 11153-11188. https://doi.org/10.1021/acscatal.9b03226
  10. Guofang Li, Nicole S. Sampson. Alternating Ring-Opening Metathesis Polymerization (AROMP) of Hydrophobic and Hydrophilic Monomers Provides Oligomers with Side-Chain Sequence Control. Macromolecules 2018, 51 (11) , 3932-3940. https://doi.org/10.1021/acs.macromol.8b00562
  11. Lei Chen, Liqiang Li, and Nicole S. Sampson . Access to Bicyclo[4.2.0]octene Monomers To Explore the Scope of Alternating Ring-Opening Metathesis Polymerization. The Journal of Organic Chemistry 2018, 83 (5) , 2892-2897. https://doi.org/10.1021/acs.joc.8b00054
  12. Eun Sil Jang, Jeremy M. John, and Richard R. Schrock . Synthesis of cis,syndiotactic-A-alt-B Copolymers from Enantiomerically Pure Endo-2-Substituted-5,6-Norbornenes. Journal of the American Chemical Society 2017, 139 (14) , 5043-5046. https://doi.org/10.1021/jacs.7b01747
  13. Eun Sil Jang, Jeremy M. John, and Richard R. Schrock . Synthesis of Cis,syndiotactic A-alt-B Copolymers from Two Enantiomerically Pure Trans-2,3-Disubstituted-5,6-Norbornenes. ACS Central Science 2016, 2 (9) , 631-636. https://doi.org/10.1021/acscentsci.6b00200
  14. Kathlyn A. Parker and Nicole S. Sampson . Precision Synthesis of Alternating Copolymers via Ring-Opening Polymerization of 1-Substituted Cyclobutenes. Accounts of Chemical Research 2016, 49 (3) , 408-417. https://doi.org/10.1021/acs.accounts.5b00490
  15. Hyangsoo Jeong, Jeremy M. John, and Richard R. Schrock . Formation of Alternating trans-A-alt-B Copolymers through Ring-Opening Metathesis Polymerization Initiated by Molybdenum Imido Alkylidene Complexes. Organometallics 2015, 34 (20) , 5136-5145. https://doi.org/10.1021/acs.organomet.5b00709
  16. Benjamin R. Elling and Yan Xia . Living Alternating Ring-Opening Metathesis Polymerization Based on Single Monomer Additions. Journal of the American Chemical Society 2015, 137 (31) , 9922-9926. https://doi.org/10.1021/jacs.5b05497
  17. Li Tan, Guofang Li, Kathlyn A. Parker, and Nicole S. Sampson . Ru-Catalyzed Isomerization Provides Access to Alternating Copolymers via Ring-Opening Metathesis Polymerization. Macromolecules 2015, 48 (14) , 4793-4800. https://doi.org/10.1021/acs.macromol.5b01058
  18. Hyangsoo Jeong, Jeremy M. John, Richard R. Schrock, and Amir H. Hoveyda . Synthesis of Alternating trans-AB Copolymers through Ring-Opening Metathesis Polymerization Initiated by Molybdenum Alkylidenes. Journal of the American Chemical Society 2015, 137 (6) , 2239-2242. https://doi.org/10.1021/jacs.5b00221
  19. Subhajit Pal, Mahshid Alizadeh, Phally Kong, Andreas F. M. Kilbinger. Oxanorbornenes: promising new single addition monomers for the metathesis polymerization. Chemical Science 2021, 12 (19) , 6705-6711. https://doi.org/10.1039/D1SC00036E
  20. Jingling Zhang, Xiaoxi Yu, Bingqian Zheng, Jiachun Shen, Surita R. Bhatia, Nicole S. Sampson. Cationic amphiphilic alternating copolymers with tunable morphology. Polymer Chemistry 2020, 11 (34) , 5424-5430. https://doi.org/10.1039/D0PY00782J
  21. Jessica K. Su, Zexin Jin, Rui Zhang, Gang Lu, Peng Liu, Yan Xia. Tuning the Reactivity of Cyclopropenes from Living Ring‐Opening Metathesis Polymerization (ROMP) to Single‐Addition and Alternating ROMP. Angewandte Chemie 2019, 131 (49) , 17935-17940. https://doi.org/10.1002/ange.201909688
  22. Jessica K. Su, Zexin Jin, Rui Zhang, Gang Lu, Peng Liu, Yan Xia. Tuning the Reactivity of Cyclopropenes from Living Ring‐Opening Metathesis Polymerization (ROMP) to Single‐Addition and Alternating ROMP. Angewandte Chemie International Edition 2019, 58 (49) , 17771-17776. https://doi.org/10.1002/anie.201909688
  23. Benjamin R. Elling, Jessica K. Su, John D. Feist, Yan Xia. Precise Placement of Single Monomer Units in Living Ring-Opening Metathesis Polymerization. Chem 2019, 5 (10) , 2691-2701. https://doi.org/10.1016/j.chempr.2019.07.017
  24. Veronica Paradiso, Fabia Grisi. Ruthenium‐Catalyzed Alternating Ring‐Opening Metathesis Copolymerization of Norborn‐2‐ene with Cyclic Olefins. Advanced Synthesis & Catalysis 2019, 361 (17) , 4133-4139. https://doi.org/10.1002/adsc.201900565
  25. Yaqi Wang, Yu Chen, Zhiqiang Jiang, Fang Liu, Fang Liu, Yuanyuan Zhu, Yong Liang, Zongquan Wu. Halogen effects on phenylethynyl palladium(II) complexes for living polymerization of isocyanides: a combined experimental and computational investigation. Science China Chemistry 2019, 62 (4) , 491-499. https://doi.org/10.1007/s11426-018-9415-8
  26. Xiaoxia Zhao, Jinshan Bai, Fanyun Zeng, Yufeng Xing, Ranran Zhu, Jianhui Huang. Direct Double Arylation of Bridged Alkenes and Efficient Bis-C-H Alkylation of Benzamides. ChemistrySelect 2018, 3 (28) , 8040-8044. https://doi.org/10.1002/slct.201801801
  27. Daijiro Hayashi, Yuta Igura, Yoichi Masui, Makoto Onaka. Stabilization and activation of unstable propynal in the zeolite nanospace and its application to addition reactions. Catalysis Science & Technology 2017, 7 (19) , 4422-4430. https://doi.org/10.1039/C7CY01161J
  28. Shaofei Song, Zhisheng Fu, Junting Xu, Zhiqiang Fan. Synthesis of functional polyolefins via ring-opening metathesis polymerization of ester-functionalized cyclopentene and its copolymerization with cyclic comonomers. Polymer Chemistry 2017, 8 (38) , 5924-5933. https://doi.org/10.1039/C7PY01330B
  29. James W. Herndon. The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014. Coordination Chemistry Reviews 2016, 317 , 1-121. https://doi.org/10.1016/j.ccr.2015.09.012
  30. Dafni Moatsou, Amit Nagarkar, Andreas F. M. Kilbinger, Rachel K. O'Reilly. Degradable precision polynorbornenes via ring-opening metathesis polymerization. Journal of Polymer Science Part A: Polymer Chemistry 2016, 54 (9) , 1236-1242. https://doi.org/10.1002/pola.27964
  31. Kun Liu, Lei Ren, Qing He, Wei Jian Xu. Synthesis of Copolymers by Living Carbanionic Alternating Copolymerization. Macromolecular Rapid Communications 2016, 37 (9) , 752-758. https://doi.org/10.1002/marc.201600009
  32. Amit A. Nagarkar, Andreas F. M. Kilbinger. Catalytic living ring-opening metathesis polymerization. Nature Chemistry 2015, 7 (9) , 718-723. https://doi.org/10.1038/nchem.2320

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. Monomers employed in alternating ring-opening metathesis polymerization.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. Kinetic monitoring of ring-opening metathesis of monomers 1 and 3–5. Monomer and Grubbs III catalyst were mixed in a 1:1 ratio, [A] = [Grubbs III] = 0.03 M. Percent conversion was determined by 1H NMR spectroscopy and integration of the Ru alkylidene α proton resonance relative to the methyl ester resonances (Supporting Information). t1/2 were obtained from the plot, monomer 1: t1/2 = 40 min, monomer 3: t1/2 = 25 min, monomer 4: t1/2 = 100 min; monomer 5: t1/2 = 300 min. Each experiment was performed at least twice, and data from representative experiments are shown.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. Alternating ring-opening metathesis polymerization (AROMP) of monomers 4 and 6. The region of 1H NMR spectra in which backbone olefinic hydrogen resonances of poly(4-alt-6)n appear is shown. (a) Polymer product prepared from cyclohexene and dissolved in CDCl3. The ratio of H1:H3:H4 is 1:1:1. (b) Polymer product prepared from cyclohexene-d10 and dissolved in CD2Cl2. The ratio of H1:H3:H4 is 0:1:0. poly(4-alt-6-d10)n was dissolved in CD2Cl2 instead of CDCl3 to allow accurate integration of the phenyl resonances.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. Alternating ring-opening metathesis (AROM-1) of monomers 3 and 6 and monomers 4 and 6. The carbene regions of 13C NMR spectra of (3-alt-6)1 (left) and (4-alt-6)1 (right) are shown. In the top spectra, [Ru] catalyst was mixed with 3 or 4 in CD2Cl2 for 10–12 h. Cyclohexene was added after >90% of Ru catalyst was consumed. The 6 + [Ru]-3 reaction was monitored for 300 min, and 6 + [Ru]-4 reaction was monitored for 30 h. The 13C NMR spectrum of 6 + [Ru]-3 was acquired 30–50 min after addition of cyclohexene, and the 13C NMR spectrum of 6 + [Ru]-4 was acquired 50–70 min after addition of cyclohexene. Each experiment was performed at least twice, and data from representative experiments are shown.

    High Resolution Image
    Download MS PowerPoint Slide

    Scheme 1

    Scheme 1. (a) Alternating Ring-Opening Metathesis (AROM-1) of 3 or 4 with Cyclohexene To Form BA Dimer and Proposed Intra- and Intermolecular Cross-Metathesis for (3-alt-6)1;a (b) Double Alternating Ring-Opening Metathesis (AROM-2) To Form BA′BA Tetramerb
    High Resolution Image
    Download MS PowerPoint Slide

    Scheme aCarbenes (circled) were monitored by 13C NMR spectroscopy (Figure 4).

    Scheme bThe proton resonances monitored are colored red (Figure 5).

    Figure 5

    Figure 5. Kinetic monitoring of double ring-opening metathesis (AROM-2) reactions of monomer A (3 or 4) with [Ru]-6-A (Scheme 1b). Time zero corresponds to the addition of 1 equiv of monomer A′ (3 or 4) to 1 equiv of [Ru]-6-A in the presence of excess cyclohexene 6. Mole fraction of Ru alkylidene at 19.0 ppm was determined by integration of the Ru alkylidene resonance relative to the methyl ester resonances between 3.5 and 3.8 ppm. The mole percent of [Ru]-6-A at time zero was only 30–42% due to the low concentrations, and thus, the extended reaction times used in the initial AROM to generate [Ru]-6-A. Each experiment was performed at least twice, and data from representative experiments are shown.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    ARTICLE SECTIONS
    Jump To

    This article references 50 other publications.

    1. 1
      Siegwart, D. J.; Oh, J. K.; Matyjaszewski, K. Prog. Polym. Sci. 2012, 37, 18
      [Crossref], [PubMed], [CAS], Google Scholar
      1
      ATRP in the design of functional materials for biomedical applications
      Siegwart, Daniel J.; Oh, Jung Kwon; Matyjaszewski, Krzysztof
      Progress in Polymer Science (2012), 37 (1), 18-37CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Ltd.)
      A review. Atom Transfer Radical Polymn. (ATRP) is an effective technique for the design and prepn. of multifunctional, nanostructured materials for a variety of applications in biol. and medicine. ATRP enables precise control over macromol. structure, order, and functionality, which are important considerations for emerging biomedical designs. This article reviews recent advances in the prepn. of polymer-based nanomaterials using ATRP, including polymer bioconjugates, block copolymer-based drug delivery systems, cross-linked microgels/nanogels, diagnostic and imaging platforms, tissue engineering hydrogels, and degradable polymers. It is envisioned that precise engineering at the mol. level will translate to tailored macroscopic phys. properties, thus enabling control of the key elements for realized biomedical applications.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVaqt7%252FM&md5=b82732d7335993e45d7642a0855cb7af
    2. 2
      Jeong, B.; Bae, Y. H.; Lee, D. S.; Kim, S. W. Nature 1997, 388, 860
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    3. 3
      Cölfen, H. Macromol. Rapid Commun. 2001, 22, 219
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    4. 4
      Schacher, F. H.; Rupar, P. A.; Manners, I. Angew. Chem., Int. Ed. 2012, 51, 7898
      [Crossref], [CAS], Google Scholar
      4
      Functional Block Copolymers: Nanostructured Materials with Emerging Applications
      Schacher, Felix H.; Rupar, Paul A.; Manners, Ian
      Angewandte Chemie, International Edition (2012), 51 (32), 7898-7921CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Recent advances in polymer synthesis have significantly enhanced the ability to rationally design block copolymers with tailored functionality. The self-assembly of these macromols. in the solid state or in soln. allows the formation of nanostructured materials with a variety of properties and potential functions. This Review illustrates recent progress in the field of block copolymer materials by highlighting selected emerging applications.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVGgtrbF&md5=f8f2f0c24ac928d2f89f091a18db442e
    5. 5
      Furuta, P. T.; Deng, L.; Garon, S.; Thompson, M. E.; Frechet, J. M. J. Am. Chem. Soc. 2004, 126, 15388
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    6. 6
      Furuta, P.; Brooks, J.; Thompson, M. E.; Fréchet, J. M. J. J. Am. Chem. Soc. 2003, 125, 13165
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    7. 7
      Kim, H. K.; Baek, N. S.; Paik, K. L.; Lee, Y.; Lee, J. H. In Chromogenic Phenomena in Polymers; American Chemical Society: Washington, DC, 2004; Vol. 888, p 247.
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    8. 8
      ten Brummelhuis, N.; Weck, M. ACS Macro Lett. 2012, 1, 1216
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      8
      Orthogonal Multifunctionalization of Random and Alternating Copolymers
      ten Brummelhuis, Niels; Weck, Marcus
      ACS Macro Letters (2012), 1 (10), 1216-1218CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      A series of copolymers with varying degrees of alternation are synthesized by free-radical polymn. from 2,3,4,5,6-pentafluorostyrene (PFS) and propargyl-contg. styrene derivs. The degree of alternation varied with the electronic nature of the styrene deriv.: random copolymers were obtained using monomers with electron withdrawing moieties, whereas increasingly alternating copolymers were obtained by increasing the electron donating nature of the substituent. The copolymers could be functionalized in an orthogonal fashion using a nucleophilic substitution (with thiols) to functionalize PFS and the copper-catalyzed 3 + 2 cycloaddn. between azides and the alkyne of the propargyl groups. This methodol. allows for the facile synthesis of functional alternating copolymers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVGisLjP&md5=9e297fd69a0fcd80e78fdb227a6caad7
    9. 9
      Romulus, J.; Tan, L.; Weck, M.; Sampson, N. S. ACS Macro Lett. 2013, 2, 749
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      9
      Alternating Ring-Opening Metathesis Polymerization Copolymers Containing Charge-Transfer Units
      Romulus, Joy; Tan, Li; Weck, Marcus; Sampson, Nicole S.
      ACS Macro Letters (2013), 2 (8), 749-752CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      Alternating copolymers derived from the ring-opening metathesis polymn. (ROMP) of functionalized cyclobutene esters (CBEs) and cyclohexenes were described. The copolymer poly(CBE-alt-CH)n contains alternating side chains based on dialkoxynaphthalene and pyromellitic dianhydride. Characterization by UV-vis spectroscopy showed that the copolymers exhibit an increase in charge-transfer intensity in comparison to previously reported alternating copolymers. The bulky side chains inhibit backbiting during the polymn. and allow for enhanced control over the polymn. in comparison to copolymers functionalized with linear alkyl groups.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXht1WisrvL&md5=5ef262306acc65e1de63e9950428b4d9
    10. 10
      Lutz, J.-F.; Kirci, B.; Matyjaszewski, K. Macromolecules 2003, 36, 3136
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      10
      Synthesis of well-defined alternating copolymers by controlled/living radical polymerization in the presence of Lewis acids
      Lutz, Jean-Francois; Kirci, Betul; Matyjaszewski, Krzysztof
      Macromolecules (2003), 36 (9), 3136-3145CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Several controlled/living radical polymn. (CRP) techniques (atom transfer radical polymn. (ATRP), nitroxide-mediated polymn. (NMP), iodide degenerative transfer polymn. (IDTP), and reversible addn.-fragmentation transfer polymn. (RAFT)) were studied for the alternating copolymn. of a donor monomer (styrene) and an acceptor monomer (Me methacrylate or Me acrylate) complexed with Lewis acid. RAFT polymn. was found to be the most versatile system. The combination of RAFT and Lewis acids complexation techniques allows synthesis of well-defined alternating copolymers poly(styrene-alt-Me methacrylate) with controlled mol. wt. (up to Mn = 70 000 g mol-1), low polydispersities (Mw/Mn < 1.3), and controlled comonomer sequences (∼90% of alternating triads). These results were obtained in the presence of diethylaluminum chloride and ethylaluminum sesquichloride. Moreover, the alternating copolymers obtained in such copolymns. retain chain end functionality and were used as macroinitiators for the synthesis of well-defined diblock copolymers poly(Me methacrylate-alt-styrene)-b-polystyrene.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXis1Ohur8%253D&md5=271ae41fbae52783d72b8c4d362e43e8
    11. 11
      Chen, G.-Q.; Wu, Z.-Q.; Wu, J.-R.; Li, Z.-C.; Li, F.-M. Macromolecules 1999, 33, 232
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    12. 12
      Shirota, Y.; Yoshimura, M.; Matsumoto, A.; Mikawa, H. Macromolecules 1974, 7, 4
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    13. 13
      Kamigaito, M.; Ando, T.; Sawamoto, M. Chem. Rev. 2001, 101, 3689
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      13
      Metal-Catalyzed Living Radical Polymerization
      Kamigaito, Masami; Ando, Tsuyoshi; Sawamoto, Mitsuo
      Chemical Reviews (Washington, D. C.) (2001), 101 (12), 3689-3745CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review on the discovery and the subsequent fast development of living radical polymns. catalyzed by transition metal complexes in the period from 1994 to early 2001.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXovFagtrg%253D&md5=f3637af46a7c4fb5734f4211c8671dd7
    14. 14
      Moad, G.; Rizzardo, E.; Thang, S. H. Aust. J. Chem. 2012, 65, 985
      [Crossref], [CAS], Google Scholar
      14
      Living Radical Polymerization by the RAFT Process - A Third Update
      Moad, Graeme; Rizzardo, Ezio; Thang, San H.
      Australian Journal of Chemistry (2012), 65 (8), 985-1076CODEN: AJCHAS; ISSN:0004-9425. (CSIRO Publishing)
      A review. This paper provides a third update to the review of reversible deactivation radical polymn. (RDRP) achieved with thiocarbonylthio compds. (ZC(=S)SR) by a mechanism of reversible addn.-fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379). The first update was published in Nov. 2006 (Aust. J. Chem. 2006, 59, 669) and the second in Dec. 2009 (Aust. J. Chem. 2009, 62, 1402). This review cites over 700 publications that appeared during the period mid 2009 to early 2012 covering various aspects of RAFT polymn. which include reagent synthesis and properties, kinetics and mechanism of polymn., novel polymer syntheses, and a diverse range of applications. This period has witnessed further significant developments, particularly in the areas of novel RAFT agents, techniques for end-group transformation, the prodn. of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlWmu7%252FE&md5=ffb85869b82366af7db21722417128a8
    15. 15
      Ouchi, M.; Terashima, T.; Sawamoto, M. Chem. Rev. 2009, 109, 4963
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      15
      Transition Metal-Catalyzed Living Radical Polymerization: Toward Perfection in Catalysis and Precision Polymer Synthesis
      Ouchi, Makoto; Terashima, Takaya; Sawamoto, Mitsuo
      Chemical Reviews (Washington, DC, United States) (2009), 109 (11), 4963-5050CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. The review covers two chronol. periods: 1. 1994-2000 (460 refs.), 2 2001-2008 (970 refs.). The two periods were compared and major discoveries were summarized.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtF2ltbfK&md5=bbca8bbf872f6870f5a48d1d99cdde14
    16. 16
      Al Samak, B.; Carbill, A. G.; Hamilton, J. G.; Rooney, J. J.; Thompson, J. M. Chem. Commun. 1997, 2057
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    17. 17
      Amir-Ebrahimi, V.; Corry, D. A.; Hamilton, J. G.; Thompson, J. M.; Rooney, J. J. Macromolecules 2000, 33, 717
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    18. 18
      Amir-Ebrahimi, V.; Rooney, J. J. J. Mol. Catal. A: Chem. 2004, 208, 115
      [Crossref], [CAS], Google Scholar
      18
      Remarkable alternating effect in metathesis copolymerization of norbornene and cyclopentene using modified Grubbs ruthenium initiators
      Amir-Ebrahimi, Valia; Rooney, John J.
      Journal of Molecular Catalysis A: Chemical (2004), 208 (1-2), 115-121CODEN: JMCCF2; ISSN:1381-1169. (Elsevier Science B.V.)
      High trans and mainly cis directing Grubbs Ru initiators, I, II, III, and IV, resp. were investigated as catalysts for metathesis copolymn. of norbornene and cyclopentene. When the Lewis acid, MoCl5 or WCl6, is added to these Lewis bases initiators, I-III, a cage effect develops such that the polymers become alternating caused by the severe or almost total denial of access of norbornene to the propagating metallacarbenes. Addn. of ethers destroys the cages and removes the effect. In marked contrast the N-heterocyclic ligand Grubbs initiator, IV, does not show the effect, as addn. of MoCl5 only seems to retard the overall reaction, but does not change the copolymer compn.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXpvVWrur8%253D&md5=81a72598fa7a65661f0fae88759d4cb2
    19. 19
      Torker, S.; Müller, A.; Chen, P. Angew. Chem. 2010, 122, 3850
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    20. 20
      Bornand, M.; Torker, S.; Chen, P. Organometallics 2007, 26, 3585
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      20
      Mechanistically Designed Dual-Site Catalysts for the Alternating ROMP of Norbornene and Cyclooctene
      Bornand, Marc; Torker, Sebastian; Chen, Peter
      Organometallics (2007), 26 (14), 3585-3596CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      Mechanistic work on the olefin metathesis reaction by well-characterized ruthenium carbene complexes led to the rational design and synthesis of a modified, unsym. "first-generation" catalyst, which, in contrast to either first- or second-generation systems with sym. ligands, converts a mixt. of two cycloolefin monomers to a largely alternating copolymer. The mechanistic concept of a homogeneous catalyst that switches between more than one state at each turnover is general. The structures of the complexes, detd. by mass spectrometry, NMR, and x-ray crystallog., reveal some unexpected features, which explain sequence errors in the copolymer.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXmt1arsL4%253D&md5=15ad1e22ce39e9af70f3f48d3661792f
    21. 21
      Bornand, M.; Chen, P. Angew. Chem., Int. Ed. 2005, 44, 7909
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    22. 22
      Torker, S.; Müller, A.; Sigrist, R.; Chen, P. Organometallics 2010, 29, 2735
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    23. 23
      Vehlow, K.; Lichtenheldt, M.; Wang, D.; Blechert, S.; Buchmeiser, M. R. Macromol. Symp. 2010, 296, 44
      [Crossref], [CAS], Google Scholar
      23
      Alternating Ring-Opening Metathesis Copolymerization of Norborn-2-ene with cis-Cyclooctene and Cyclopentene
      Vehlow, Kati; Lichtenheldt, Martin; Wang, Dong-Ren; Blechert, Siegfried; Buchmeiser, Michael R.
      Macromolecular Symposia (2010), 296 (Modern Trends in Polymer Science--EPF'09), 44-48CODEN: MSYMEC; ISSN:1022-1360. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Ru-alkylidenes based on unsym. imidazolin-2-ylidenes, were used for the alternating copolymn. of norborn-2-ene (NBE) with cis-cyclooctene (COE) and cyclopentene (CPE), resp. Alternating copolymers, i.e., poly(NBE-alt-COE)n and poly(NBE-alt-CPE)n contg. up to 97 and 91% alternating diads, resp., were obtained. The copolymn. parameters of the alternating copolymn. of NBE with CPE under the action of different initiators were detd. using a first order Markov model. Hydrogenation of poly(NBE-alt-COE)n yielded a fully satd., hydrocarbon-based polymer.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsFSgtrnJ&md5=42a00dff9a615500d5a36845d47f0550
    24. 24
      Vehlow, K.; Wang, D.; Buchmeiser, M. R.; Blechert, S. Angew. Chem., Int. Ed. 2008, 47, 2615
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    25. 25
      Buchmeiser, M. R.; Ahmad, I.; Gurram, V.; Kumar, P. S. Macromolecules 2011, 44, 4098
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    26. 26
      Ilker, M. F.; Coughlin, E. B. Macromolecules 2001, 35, 54
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    27. 27
      Song, A.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2009, 131, 3444
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    28. 28
      Sutthasupa, S.; Shiotsuki, M.; Masuda, T.; Sanda, F. J. Am. Chem. Soc. 2009, 131, 10546
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    29. 29
      Choi, T.-L.; Lee, C. W.; Chatterjee, A. K.; Grubbs, R. H. J. Am. Chem. Soc. 2001, 123, 10417
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    30. 30
      Song, A.; Parker, K. A.; Sampson, N. S. Org. Lett. 2010, 12, 3729
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    31. 31
      Love, J. A.; Morgan, J. P.; Trnka, T. M.; Grubbs, R. H. Angew. Chem., Int. Ed. 2002, 41, 4035
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    32. 32
      Elsheimer, S.; Slattery, D. K.; Michael, M.; Weeks, J.; Topoleski, K. J. Org. Chem. 1989, 54, 3992
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    33. 33
      Mathias, L. J. Synthesis (Stuttgart) 1979, 561
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    34. 34
      Snider, B. B.; Rodini, D. J.; Cionn, R. S. E.; Sealfon, S. J. Am. Chem. Soc. 1979, 101, 5283
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    35. 35
      Choi, T.-L.; Grubbs, R. H. Angew. Chem., Int. Ed. 2003, 42, 1743
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    36. 36
      Baird, N. C. Tetrahedron 1970, 26, 2185
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    37. 37
      Schleyer, P. R.; Williams, J. E.; Blanchard, K. R. J. Am. Chem. Soc. 1970, 92, 2377
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      37
      Evaluation of strain in hydrocarbons. The strain in adamantane and its origin
      Schleyer, Paul von R.; Williams, James Earl, Jr.; Blanchard, K. R.
      Journal of the American Chemical Society (1970), 92 (8), 2377-86CODEN: JACSAT; ISSN:0002-7863.
      Many group-increment and bond-energy additivity schemes, e.g., the frequently employed one by Franklin, devised for calcn. of heats of formation of acyclic alkanes, are inadequate for cyclic systems. Even those schemes which treat cyclic mols. well are not applicable to defining hydrocarbon strain energies. Group increments, derived from the heats of formation of the acyclic alkanes in completely skew-free conformations, are: Me, -10.05; CH2, -5.13; CH, -2.16; C, -0.30 kcal. These "single-conformation" increments are recommended for the evaluation of strain in hydrocarbons and tables of such strain estimates are provided. A modest strain in cyclochexane (1.35 kcal/mole) and trans-Decalin (1.79 kcal/mole) is indicated. More surprising is the finding of 6.48 kcal/mole of strain in adamantane, thought previously to be a "strain-free" mol. This strain can be accounted for quant. in terms of angle strain and C...C nonbonded repulsions from which the rigidity of adamantane skeleton allows no escape, provided rather hard C...C nonbonded potential functions are employed in computer conformational anal. calcns. Softer C...C nonbonded functions are less satisfactory, as they do not reproduce well the energies and geomteries of bridged hydrocarbons. Special cage effects need not be invoked in interpreting the strain in adamantane, nor, presumably, in other bridged polycyclic mols.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3cXhtlWrtLs%253D&md5=a7b06cfb246e1c3820dda844428b16c4
    38. 38
      Wiberg, K. B. Angew. Chem., Int. Ed. 2003, 25, 312
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    39. 39
      Lee, J. C.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2006, 128, 4578
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    40. 40
      Beak, P.; Kempf, D. J.; Wilson, K. D. J. Am. Chem. Soc. 1985, 107, 4745
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    41. 41
      Allinger, N. L.; Tribble, M. T.; Miller, M. A.; Wertz, D. H. J. Am. Chem. Soc. 1971, 93, 1637
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    42. 42
      Hoyland, J. R. J. Chem. Phys. 1969, 50, 2775
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    43. 43
      Allinger, N. L.; Hirsch, J. A.; Miller, M. A.; Tyminski, I. J.; Van Catledge, F. A. J. Am. Chem. Soc. 1968, 90, 1199
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    44. 44
      Fuchs, B. In Topics in Stereochemistry; Eliel, E. L.; Wilen, S. H.; Allinger, N. L., Eds.; Interscience: 1978; Vol. 10, p 1.
      Google Scholar
      There is no corresponding record for this reference.
    45. 45
      Wilson, N. K.; Stochters, J. B.; Bucourt, R.; Kellie, G. M.; Friddell, F. G.; Moriarty, R. M. In Topics in Stereochemsitry; Eliel, E. L.; Wilen, S. H.; Allinger, N. L., Eds.; Interscience: New York, 1974; Vol. 8, p 1.
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    46. 46
      Testa, B.; Vistoli, G.; Pedretti, A. Helv. Chim. Acta 2013, 96, 564
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    47. 47
      Abraham, R. J.; Koniotou, R.; Sancassan, F. J. Chem. Soc., Perkin Trans. 2 2002, 2025
      [Crossref], [CAS], Google Scholar
      47
      Conformational analysis.Part 39. A theoretical and lanthanide induced shift (LIS) investigation of the conformations of cyclopentanol and cis- and trans-cyclopentane-1,2-diol
      Abraham, Raymond J.; Koniotou, Rodothea; Sancassan, Fernando
      Journal of the Chemical Society, Perkin Transactions 2 (2002), (12), 2025-2030CODEN: JCSPGI; ISSN:1472-779X. (Royal Society of Chemistry)
      The conformations of cyclopentanol and cis- and trans-cyclopentane-1,2-diol have been studied by ab initio and mol. mechanics (MM) calcns. and by the LIS technique, using Yb(fod)3 to obtain the induced shifts of all 1H and 13C nuclei in the mol., together with complexation shifts obtained by the use of La(fod)3. The MM calcns. gave two optimized geometries for cyclopentanol. These were envelope conformations with the hydroxyl group equatorial (1A) and axial (1B) at the flap of the envelope. In contrast Gaussian 98 at the B3LYP level with the 6-31G** basis set gave an optimized geometry (1C) which was an envelope conformation with the hydroxyl group in an axial position at the fold of the envelope. ΔE(1A - 1B) = 0.47 kcal mol-1 (MM) and 0.93 kcal mol-1 (ab initio) and ΔE (1B - 1C) = 0.15 kcal mol-1 (ab initio). The MM and ab initio calcns. for cis-1,2-cyclopentanediol gave different envelope conformations (2A) and (2B), both with one equatorial and one axial hydroxyl group. For trans-1,2-cyclopentanediol both calcns. gave the same geometries, an envelope conformation with two axial hydroxyls (3A) and a half chair conformer with diequatorial hydroxyls (3B). ΔE (3A - 3B) = 2.9 kcal mol-1 ( MM) and 0.70 kcal mol-1 (ab initio). The LIRAS4 model involving an sp3 hybridized oxygen atom with two sym. lone pairs was used for these compds. The calcd. LIS for cyclopentanol gave poor agreement with the obsd. data for 1A, moderate agreement for 1B but good agreement for 1C. A LIS anal. combining 1B and 1C suggests that the population of 1C was >80% in CHCl3 soln. The ab initio calcns. and the LIS anal. agree that the unsym. conformer 1C is the major form in soln. The similarity between this conformer of cyclopentanol and that of the furanose sugars suggests that the anomeric effect may be more fundamental than hitherto realized. In cis-cyclopentane-1,2-diol the obsd. data were in good agreement with the calcd. LIS for both 2A and 2B. In trans-cyclopentane-1,2-diol the obsd. data were in good agreement with the calcd. LIS for 3B but in poor agreement for 3A. The LIS allowed the assignment of the proton chem. shifts of the individual methylene protons in these mols. which had not been given previously.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38Xpt1ylsro%253D&md5=7985561855b8eb966e103633b41ee323
    48. 48
      Abraham, R. J.; Koniotou, R. Magn. Reson. Chem. 2003, 41, 1000
      [Crossref], [CAS], Google Scholar
      48
      Conformational analysis. Part 40:+ A theoretical and NMR investigation of the conformations of cis- and trans-cyclopentane-1,3-diol
      Abraham, Raymond J.; Koniotou, Rodothea
      Magnetic Resonance in Chemistry (2003), 41 (12), 1000-1008CODEN: MRCHEG; ISSN:0749-1581. (John Wiley & Sons Ltd.)
      The conformations of cis- (1) and trans-cyclopentane-1,3-diol (2) have been studied by ab initio (Gaussian 98) and mol. mechanics (PCMODEL) calcns. and by NMR spectroscopy. The calcns. gave two low-energy conformations for (1), 1A and 1B, both with axial hydroxyl groups. Two conformations with equatorial hydroxyl groups (1C and 1D) were found but with much higher energy (ca 4.0 kcal mol-1). Five low-energy conformers were found for 2. Four were envelope conformations and one a half-chair. The complete anal. of the 400 MHz 1H NMR spectra of 1 in a variety of solvents and 2 in chloroform was performed by extensive decoupling expts., iterative computer anal. and spectral simulation. This gave all the H,H couplings in the mol., including in 1 a long-range 4J(H,H) coupling between H-2cis and H-4,5cis. The 3J(H,H) couplings were used to det. the conformer populations in these mols. This was initially achieved using the Haasnoot, de Leeuw and Altona equation, to obtain the conformer couplings. It was found that this equation was not accurate for the C·CH2·CH2·C fragment in these mols. and the following equation was derived for this fragment from five- and six- membered cyclic compds. in fixed conformations:. 3J(H,H) = 11.16 cos2.vphi. - 1.28 cos.vphi. + 0.77. The conformer populations were obtained by calcg. the conformer couplings which were then compared with the obsd. couplings. Compd. 1 in benzene soln. is an approx. equal mixt. of conformers 1A and 1B with small (<4%) amts. of 1C and 1D. In the polar solvents acetone and acetonitrile the populations of 1A and 1B are again equal, with 20% of 1C and <2% of 1D. In 2 the major conformers are 2B and 2D with small amts. of 2C, 2E and 2A. These novel findings are considered with previous data on cyclopentanol and cis- and trans-cyclopentane-1,2-diol and it is shown that the axial hydroxyl substituent at the fold of the envelope appears to be a major factor in detg. the conformational energies of these compds.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXpsV2ms7Y%253D&md5=bc8b82b591187411eefb8b834497823f
    49. 49
      Choi, T.-L.; Rutenberg, I. M.; Grubbs, R. H. Angew. Chem., Int. Ed. 2002, 41, 3839
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    50. 50
      Romulus, J.; Patel, S.; Weck, M. Macromolecules 2011, 45, 70
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.

  • Supporting Information

    Supporting Information

    ARTICLE SECTIONS
    Jump To

    Figures showing characterization of monomers and polymer, GPC, 1D- and 2D-NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org.


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

PDF [ 1MB]

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

You’ve supercharged your research process with ACS and Mendeley!

STEP 1:
Click to create an ACS ID

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

MENDELEY PAIRING EXPIRED
Your Mendeley pairing has expired. Please reconnect