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Reversible photorheological lyotropic liquid crystals

journal contribution
posted on 2014-01-01, 00:00 authored by Shuhua Peng, Qipeng Guo, T C Hughes, P G Hartley
We describe novel lyotropic liquid-crystalline (LLC) materials based on photoresponsive amphiphiles that exhibit rapid photoswitchable rheological properties of unprecedented magnitude between solidlike and liquidlike states. This was achieved through the synthesis of a novel azobenzene-containing surfactant (azo-surfactant) that actuates the transition between different LLC forms depending on illumination conditions. Initially, the azo-surfactant/water mixtures formed highly ordered and viscous LLC phases at 20-55 wt % water content. Spectroscopic, microscopic, and rheological analysis confirmed that UV irradiation induced the trans to cis isomerization of the azo-surfactant, leading to the disruption of the ordered LLC phases and a dramatic, rapid decrease in the viscosity and modulus resulting in a 3 orders of magnitude change from a solid (20,000 Pa) to a liquid (50 Pa) at rate of 13,500 Pa/s. Subsequent exposure to visible light reverses the transition, returning the viscosity essentially to its initial state. Such large, rapid, and reversible changes in rheological properties within this LLC system may open a door to new applications for photorheological fluids.

History

Journal

Langmuir

Volume

30

Issue

3

Pagination

866 - 872

Publisher

American Chemical Society

Location

Washington, D.C.

ISSN

0743-7463

eISSN

1520-5827

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2014, American Chemical Society