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Article

A Simple Class of Photorheological Fluids: Surfactant Solutions with Viscosity Tunable by Light

Aimee M. Ketner, Rakesh Kumar, Tanner S. Davies, Patrick W. Elder, and Srinivasa R. Raghavan*

Contribution from the Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742-2111

J. Am. Chem. Soc., 2007, 129 (6), pp 1553–1559

DOI: 10.1021/ja065053g

Publication Date (Web): January 23, 2007

Section:

Surface Chemistry and Colloids

Abstract

Photorheological (PR) fluids, i.e., those with light-tunable rheological properties, may be useful in a variety of applications, such as in sensors and microfluidic devices. Currently, the need to synthesize complex photosensitive molecules hampers the applicability of these fluids. Here, we report a simple class of PR fluids that require no special synthesis and can be easily replicated in any lab from inexpensive chemicals. The fluids consist of the cationic surfactant, cetyl trimethylammonium bromide (CTAB), and the photoresponsive organic derivative, trans-ortho-methoxycinnamic acid (OMCA). Aqueous mixtures of CTAB and OMCA in basic solution self-assemble into long, wormlike micelles. Upon irradiation by UV light (<400 nm), OMCA undergoes a photoisomerization from its trans to its cis form, which alters the molecular packing at the micellar interface. The result is to transform the long micelles into much shorter entities and, in turn, the solution viscosity decreases by more than 4 orders of magnitude. Small-angle neutron scattering (SANS) is used to confirm the dramatic reduction in micellar length. The extent of viscosity reduction in these PR fluids can be tuned based on the composition of the mixture as well as the duration of the irradiation.

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This article has been cited by 13 ACS Journal articles (5 most recent appear below).

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Reversible Photorheological Fluids Based on Spiropyran-Doped Reverse Micelles
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Journal of the American Chemical Society2011 Article ASAP
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Coarse-Grained Molecular Dynamics Simulations of the Sphere to Rod Transition in Surfactant Micelles
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- Coarse-Grained Molecular Dynamics Simulations of the Sphere to Rod Transition in Surfactant Micelles
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  Surfactant molecules self-assemble in aqueous solutions to form various micellar structures such as spheres, rods, or lamellae. Although phase transitions in surfactant solutions have been studied experimentally, their molecular mechanisms are still not ...
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Light-Responsive Threadlike Micelles as Drag Reducing Fluids with Enhanced Heat-Transfer Capabilities
Haifeng Shi, Yi Wang, Bo Fang, Yeshayahu Talmon, Wu Ge, Srinivasa R. Raghavan, and Jacques L. Zakin
Langmuir2011 Article ASAP
- Light-Responsive Threadlike Micelles as Drag Reducing Fluids with Enhanced Heat-Transfer Capabilities
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Reversible Photorheology in Solutions of Cetyltrimethylammonium Bromide, Salicylic Acid, and trans-2,4,4′-Trihydroxychalcone
M. Pereira, C. R. Leal, A. J. Parola and U. M. Scheven
Langmuir2010 26 (22), 16715-16721
- Reversible Photorheology in Solutions of Cetyltrimethylammonium Bromide, Salicylic Acid, and trans-2,4,4′-Trihydroxychalcone
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  Langmuir2010 26 (22), 16715-16721
  We show photorheology in aqueous solutions of weakly entangled wormlike micelles prepared with cetyltrimethylammonium bromide (CTAB), salicylic acid (HSal), and dilute amounts of the photochromic multistate compound trans-2,4,4′-trihydroxychalcone (Ct). ...
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