Fabrication of Oxidative and pH Dual-Responsive Photonic Crystals Based on Sulfide-Containing Block Copolymers

Photonic crystals (PCs) derived from responsive polymers exhibit adjustable photonic band gaps under external stimuli, and they have abundant applications in different fields. Herein, oxidative and pH dual-responsive copolymers were synthesized using reversible addition–fragmentation chain transfer (RAFT) polymerization with a functional monomer of combined phenyl vinyl sulfide (PVS) and N,N′-(dimethylamino) ethyl acrylate (DMAEA). The oxidatively responsive PVS segment generated copolymers with a refractive index (RI) change, and the pH-responsive DMAEA segment generated copolymers with a distance change in the aggregation state. Fabricating PCs with these copolymers resulted in unique dual-responsive behavior, e.g., the reflective peaks of PCs exhibited blue shifts to varying degrees under different oxidative and pH conditions. This report presents a high refractive index polymer derived from S-vinyl sulfide derivatives, in which the refractive index changed through selective oxidation and dual responsiveness was observed when the derivatives were combined with DMAEA units. Owing to changes in the RI and the period distance in PCs, a predictable change in the band gap of PCs for the aim of realizing a dual-responsive PC sensor was successfully obtained.