Synthesis of pH-responsive block copolymer micelles via RAFT polymerization induced self-assembly and its application in emulsifier-free emulsion polymerization

Abstract

The pH-responsive amphiphilic block copolymer micelles based on poly (2-(dimethylamino) ethyl methacrylate) (PDMAEMA) as a flexible corona and poly(hexafluorobutyl acrylate) (PHFBA) as a core have been synthesized by reversible addition-fragmentation chain transfer polymerization induced self-assembly (RAFT-PISA). This core-shell type amphiphilic copolymer micelles possessed the characteristics of pH-response from pendent tertiary amine groups in PDMAEMA chain. The morphology and size of amphiphilic block copolymer micelles were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. The results indicated that the diameter of micelles narrowed down from 160 nm to 20 nm along with the increased pH value from 1.32 to 2.90. However, the diameter of the amphiphilic block copolymer micelles ranged broadly from 20 nm to more than 100 nm at pH ≥ 5.89. The amphiphilic block copolymer micelles were later used as reactors to synthesize cationic fluorinated polyacrylate emulsifier-free emulsion at pH 2.90, using fluorinated monomers and acrylate monomers as mixed monomers. The latex particles were presented as core-shell morphology with diameter of about 220 nm and narrow distribution, as characterized by TEM and DLS. The obtained emulsion with high zeta potential (+57.8 mV) had excellent stability.