Surfactant-Free Visible-Light-Controlled Emulsion Polymerization toward ABA-Type Amphiphilic Triblock Copolymers

Abstract

Surfactant-free visible-light-controlled emulsion polymerizations are demonstrated here to synthesize ABA-type amphiphilic triblock copolymers, where A represents the hydrophilic block of poly(acrylic acid) (PAA) and B represents the hydrophobic block, such as poly(butyl acrylate) (PBA), poly(ethyl acrylate) (PEA), poly(trifluoroethyl acrylate) (PTFEA), and poly(hexafluorobutyl acrylate) (PHFBA). The photoiniferter solution polymerization of acrylic acid (AA) in 1,4-dioxane was first performed under air atmosphere and successfully controlled by visible light with the existence of iniferter agent and ascorbic acid. Using the as-synthesized PAA with trithioester end-groups as macro-iniferter agent, ABA-type triblock copolymers were synthesized in an aqueous emulsion system. Chain growth of various hydrophobic B blocks induced self-assembly and micellization. The micelles were in turn swelled by monomers and acted as main reaction loci for the further photoiniferter emulsion polymerizations. All the polymeri...