Modulating the Solution Phase Behavior of a Block Polymer with Light

Polymer solutions that are able to respond to external stimuli such as temperature or light have found applications ranging from sensors to optical devices. To enable the rational design of responsive materials, our work explores the solution phase behavior of a block polymer that is both thermo- and photoresponsive. The addition of a solvent that selectively swells one block provides a route to tuning the effective volume fraction of the blocks, and this selectivity can be controlled by both temperature and light exposure. The block polymer poly(methyl methacrylate)-block-poly(benzyl methacrylate-stat-(4-phenylazophenyl methacrylate)) (PMMA-b-P(BzMA-stat-AzoMA)) in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide displays these photoresponsive properties. The PMMA block is soluble in the ionic liquid, while the solubility of the P(BzMA-stat-AzoMA) block can be tuned by both temperature and light.