Cosolvent incorporation tunes the nanostructure formation and thermal responsivity of aqueous PNIPAM/silyl methacrylate copolymers

Polymers functionalized with inorganic silane groups have been used in a wide range of applications due to the silane reactivity. Stimuli-responsive polymers in these hybrid systems can be used for applications including sensing and optical coatings. Of particular interest is the thermoresponsive poly(N-isopropyl acrylamide) (PNIPAM) functionalized with 3-(trimethoxysilyl)propyl methacrylate (TMA), which has demonstrated unique aqueous thermal and optical responses. We previously showed that localizing the TMA in blocky domains led to the formation of uniform structures above the cloud point temperature, in comparison to disperse aggregates from random copolymers. Blocky localization also led to greater thermal cyclability than in random copolymers. Here, we investigate the role of solvent species and content on the size and dispersity of structures formed above the cloud point temperature in blocky-functionalized and random copolymers. Mixtures of solvents can introduce additional phase transitions and alter the phase boundaries based on temperature and composition. Cosolvent incorporation alters the aggregation of NIPAM/TMA copolymers, changing size and dispersity. Additionally, the optical response and cyclability depends on the copolymer composition and the cosolvent content. Cosolvent incorporation thus increases the versatility of inorganic-functionalized responsive polymers by providing a simple way to tune the structure size and response, leading to distinct applications.