Light-Triggered Programming of Hydrogel Properties Using Sleeping Photoactive Polymer Nanoparticles

A key characteristic of programmable hydrogels is that their physical and chemical properties can be changed postsynthetically. In order to achieve this, we used sub-50 nm photoacid/base generator nanoparticles, which could alter the charge density/polarity a host macroscopic hydrogel (e.g., polyacrylamide). The photoacid (PAG) were composed poly(methyl methacrylate-co-4,5-dimethoxy-2-nitrobenzyl methacrylate-co-1,6-hexanediol diacrylate) exhibited pH-dependent swelling behavior when they irradiated with UV light. Thus, using PAG nanoparticles enabled space-selective light-triggered by increasing density at alkaline pH. Using photobase (PBG) consisting methacrylate-co-2-nitrobenzyl methyl 4-methacryloyloxy piperidine-1-carboxylate-co-1,6-hexanediol diacrylate), it was possible space-selectively produce positive charge, acidic pH, within network. PBG added several functionalities hydrogel, including reversible writing/erasing patterns as well postpolymerization in desired sites. Including mixtures caused deswelling upon UV-irradiation. By mass fraction PAG/PBG effect limited only top surface area, resulting monolayer actuator large bending angle. This study has successfully demonstrated excellent potential confer photoresponsive behaviors transform nonresponsive into responsive on demand. system spatially tailored provide wide range useful such initiation sites for synthesis, writing/erasing, actuation.