Synthesis and Study of Thermoresponsive Amphiphilic Copolymers via RAFT Polymerization

Synthesis and study of well-defined thermoresponsive amphiphilic copolymers with various compositions were reported. Kinetics of the reversible addition-fragmentation chain transfer (RAFT) (co)polymerization of styrene (St) and oligo(ethylene glycol) methyl ether methacrylate (PEO(5)MEMA) was studied by size exclusion chromatography (SEC) and H-1 NMR spectroscopy, which allows calculating not only (co)polymerization parameters but also gives valuable information on RAFT (co)polymerization kinetics, process control, and chain propagation. Molecular weight M-n and dispersity D of the copolymers were determined by SEC with triple detection. The detailed investigation of styrene and PEO(5)MEMA (co)polymerization showed that both monomers prefer cross-polymerization due to their low reactivity ratios (r(1) < 1, r(2) < 1); therefore, the distribution of monomeric units across the copolymer chain of p(St-co-PEO(5)MEMA) with various compositions is almost ideally statistical or azeotropic. The thermoresponsive properties of p(St-co-PEO(5)MEMA) copolymers in aqueous solutions as a function of different hydrophilic/hydrophobic substituent ratios were evaluated by measuring the changes in hydrodynamic parameters under applied temperature using the dynamic light scattering method (DLS).