Synthesis of Amphiphilic Block Copolymers Based on SKA by RAFT Polymerization

Abstract : Temperature-sensitive amphiphilic block copolymers of 2,2-dimethyl-1,3-dioxolan-4-yl-methyl acrylate (solketal acrylate, SKA) and N-isopropyl acrylamide (NIPAAm) have been prepared via reversible addition-fragmentation chain transfer radical polymerization (RAFT). A kinetics study of SKA polymerization is performed in order to find a compatible RAFT chain transfer agents (CTA) and versatile polymerization conditions for the synthesis of well-defined poly(2,2-dimethyl-1,3-dioxolan-4-yl-methyl acrylate) (PSKA). Depending on the RAFT-CTA and the reaction time, PSKA with molar masses up to 5700 g mol−1 and dispersity values as low as 1.1 could be prepared. Additionally, the end group distribution of PSKA is investigated via electrospray ionization-ion mobility separation–mass spectrometry. The chain extensions of the homopolymers for the second block of NIPAAm are analyzed with size-exclusion chromatography. Amphiphilic block copolymers are obtained after hydrolysis of hydrophobic PSKA block to target hydrophilic poly(2,3-dihydroxypropyl acrylate) block.