Gold nanoparticles for smart and recoverable catalyst using thermo-responsive core-crosslinked star polymer as the nanoreactor

In this work, a novel kind of temperature-responsive core cross-linked star (CCS) polymer, composing of poly(methoxypolyethylene glycol-co-di(ethylene glycol) ethyl ether acrylate) (P(PEGA-DEGA)) as thermo-responsive arm and poly(2-(dimethylamino)ethyl methacrylate) as functional core, was developed as nanoreactor for immobilizing gold nanoparticles for smart catalyst with facile recovery. The protonated imino groups in CCS polymer core could capture AuCl 4 - and simultaneously reduce it to Au NPs in aqueous solution, leading to the formation of P(PEGA-DEGA) CCS@Au composite. The whole procedure was carried out in aqueous media without using any toxic reducing agent, which is facile, efficient and green. The as-prepared CCS@Au composite exhibit a superior high catalytic activity for the reduction of 4-nitrophenol (4-NP), owing to that the soluble polymeric arms of the CCS polymers provides a homogeneous reaction system with fast mass transfer and thus facilitates interactions between Au NPs in the core and 4-NP. In addition, temperature-responsive catalyzing behavior was observed for the CCS@Au composite: the reaction rate enhanced with the elevation of the reaction temperature at first, but decreased when the temperature increased close to the LCSTs of the CCS@Au catalysts.