Temperature and pH-Dual Responsive AIE-Active Core Crosslinked Polyethylene–Poly(methacrylic acid) Multimiktoarm Star Copolymers

A series of aggregation-induced emission (AIE) active core crosslinked miktoarm star copolymers, having multi polyethylene (PE) and poly(methacrylic acid) (PMAA) arms, were synthesized and their thermal/pH responsive properties were studied. The procedure involves (a) the synthesis of PE-Br by polyhomologation of dimethylsulfoxonium methylide with triethylborane as initiator, followed by oxidation-hydrolysis/esterification reactions and of poly(tert-butyl methacrylate) (PtBMA-Br) by atom transfer radical polymerization (ATRP) of tert-butyl methacrylate, (b) the synthesis of (PE)_n-(PtBMA)_m-P(TPE-2St) by ATRP of a double styrene-functionalized tetraphenylethene (TPE-2St) with PE-Br and PtBMA-Br macroinitiators, and (c) the hydrolysis of (PE)_n-(PtBMA)_m-P(TPE-2St) to afford the amphiphilic miktoarm star copolymers (PE)_n-(PMMA)_m-P(TPE-2St). Due to their spherical core-shell structure (temperature-responsive) and the presence of hydrophilic PMAA (pH-responsive) and TPE-2St (AIE), these miktoarm star copolymers are AIE materials with temperature/pH-dual responsivity. In addition, thanks to the coexistence of hydrophilic and hydrophobic arms, these materials promote stable water-in-oil emulsions.