Dual responsive macroemulsion stabilized by Y-shaped amphiphilic AB2 miktoarm star copolymers

Abstract

Dual responsive macroemulsions stabilized by Y-shaped amphiphilic AB₂ miktoarm star polymeric emulsifiers were presented in this study. First, a amphiphilic Y-shaped AB₂ miktoarm star polymer composed of poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) and polystyrene (PS) arms was synthesized by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene monomer and atom transfer radical polymerization (ATRP) of N,N-dimethylaminoethyl methacrylate (DMAEMA) monomer. The structure and the molecular weight as well as the molecular weight distribution were carefully characterized by ¹H NMR and GPC, respectively. The obtained PS–(PDMAEMA)₂ miktoarm star polymers were then applied as polymer emulsifiers for both o/w and w/o macroemulsions formation, and stabilized macroemulsions could be produced at a lower emulsifier content. Meanwhile, the emulsifying performance of PS–(PDMAEMA)₂ miktoarm star polymer and stimulus-response of the macroemulsion were also investigated. The PS–(PDMAEMA)₂ stabilized o/w macroemulsion showed pH-induced demulsification and temperature-induced phase inversion. However, the inversion of the PS–(PDMAEMA)₂ emulsifier at the oil–water interface could not be spontaneously accomplished. Furthermore, successful phase inversion was only smoothly realized for those emulsions with pH 7 water in the presence of a modulate stirring.