Synthesis and surface activity of novel amphiphilic block copolymers based on methacrylate by group-transfer polymerization

Abstract

Living polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) which contains tertiary amino functional group was achieved by group-transfer polymerization(GTP). The resulting polymer had the controlled molecular weight and narrow molecular weight distribustion. Di-, and triblock copolymers were prepared easily by sequential addition of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) or butyl methacrylate (BMA) using mono- and difunctional initiator at room temperature. The resulting polymers, as a class of non-ionic polymeric surfactant, exhibited excellent surface activity and lowered the surface tension of their aqueous solutions. Their molecular weight and composition could be controlled by regulating the ratio of monomer to initiator and the feed ratio of two monomers, respectively. The extent of the surface tension lowering was affected by molecular weight and composition of block copolymers. The optimum composition for the highest surface activity was varied with molecular weight. The lowest $\gamma$ value reached to 23.1 dyn/cm in the ABA type triblock copolymer of 1,000 (g/mol) of molecular weight. Polymer reactions of poly(DMAEMA) with iodomethane and with 1,4-butane sultone were studied. The degree of conversion of the amine pendant group determined by $^1$H NMR was quantitative in both cases. Different amphiphilic triblock copolymers of hydrophobic n-butyl methacrylate (BMA) and hydrophilic 2-methacryloyloxyethyltrimethyl ammonium iodide were prepared by the reaction of precursor polymer and iodomethane. The precursor polymers were obtained by Group-Transfer Polymerization (GTP) of BMA with 2-(dimethylamino)ethyl methacrylate (DMAEMA) using a difunctional initiator at room temperature. Their molecular weight and composition could be controlled by regulating the monomer to initiator ratio and the feed ratio of two monomers. From quantitative quaternarization of poly(DMAEMA) segments of precusor polymers by iodomethan...