Synthesis and characterization of rigid functional anionic polyelectrolytes: Block copolymers and star homopolymers

Abstract

Seven cyclolinear polymers bearing the tertiary-butyl α- (hydroxymethyl)acrylate (TBHMA) ether dimer were prepared using reversible addition-fragmentation chain transfer (RAFT) polymerization. Of the seven polymers, five were cyclolinear homopolymers of the TBHMA ether dimer with different degrees of polymerization, one was an "arm-first" star homopolymer, and the other was an amphiphilic linear copolymer based on the positively ionizable hydrophilic 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the TBHMA ether dimer. For comparison, two more polymers were prepared using RAFT polymerization where the TBHMA ether dimer was replaced by tertiary-butyl methacrylate (tBuMA). In particular, an amphiphilic linear DMAEMA-tBuMA diblock copolymer and a tBuMA arm-first star homopolymer were also synthesized. All polymers were characterized in terms of their molecular weights and composition using gel permeation chromatography and 1H NMR spectroscopy, respectively. Subsequently, the tertiary-butyl groups of the TBHMA ether dimer units and those of the tBuMA units were cleaved by hydrolysis to yield carboxylic acid groups. The successful removal of the tertiary-butyl groups was confirmed using 1H and 13C NMR and attenuated total reflectance-Fourier transform infrared spectroscopies. The hydrolyzed (co)polymers exhibited pK values of the carboxylic acid groups of around 4.5, and glass transition temperatures, T g, of around 200 °C, which were 50 °C higher than those of their nonhydrolyzed precursors. © 2011 Wiley Periodicals, Inc.