Controllable synthesis of P(NIPAM-co-MPTMS)/PAA–Au composite materials with tunable LSPR performance

Loading of Au nanoparticles (AuNPs) onto environmentally sensitive polymer microgels is increasingly used to regulate their optical properties and catalytic activities. Herein, we synthesized composite polymer microgels composed of poly(N-isopropylacrylamide-co-3-methacryloxypropyltrimethoxysilane)/poly(acrylic acid) with a core–shell structure, and AuNPs were controllably loaded onto/into the network chains of the polymer microgels using seed-mediated growth. The prepared AuNPs composite materials possessed good pH sensitivity; the electromagnetic coupling between the AuNPs could thus be tuned via the swelling/deswelling of the polymer microgels under various acidic/alkaline conditions. More importantly, the coordination interaction between the carboxyl groups in the PAA chains and Cu²⁺ ions changed by varying the copper ion content under various pH conditions, thus enabling regulation of the localized surface plasmon resonance of the AuNPs. These structural features of the prepared composite microgels enabled to tailor the optical performance of the AuNPs by varying the pH of the surrounding medium.