Photo-stimuli responsive materials are of interest for a broad range of applications, and take advantage of the inherently non-invasive, spatially resolved, and species-selective optical response. We demonstrate here photo-reversible micellization/de-micellization, gelation, and order-disorder transitions in block copolymer/ionic liquid systems. The general strategy involves one block that is well solvated in the ionic liquid of interest, such as poly(ethylene oxide) and poly(methyl methacrylate), and another that has exhibits either UCST (such as poly(N-isopropylacrylamide)) or LCST (poly(benzyl methacrylate)) behavior. A few mole percent of azomethacrylate is incorporated statistically into the temperature-responsive block. Under UV irradiation, the trans to cis photoisomerization of azobenzene significantly increases the solubility of the thermoresponsive block, leading to a structural transition at appropriate concentrations and temperatures. Under visible light, the cis to trans recovery causes the sample to revert to the original state. The progress of the transition is monitored by in situ photo-rheology and scattering techniques.

Photo-induced structural transitions in block copolymers

2019 Spring National Meeting

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