Poly(hydroxyl propyl methacrylate)-b-Poly(oligo ethylene glycol methacrylate) Thermoresponsive Block Copolymers by RAFT Polymerization

Thermoresponsive amphiphilic poly(hydroxyl propyl methacrylate)-b-poly(oligo ethylene glycol methacrylate) block copolymers (PHPMA-b-POEGMA) are synthesized by RAFT polymerization, with different compositions and molecular weights. The copolymers are molecularly characterized by size-exclusion chromophotography, and H-1 NMR spectroscopy. Dynamic light scattering (DLS) and static light scattering (SLS) experiments in aqueous solutions show that the copolymers respond to temperature variations via formation of self-organized nanoscale aggregates. Aggregate structural characteristics depend on copolymer composition, molecular weight, and ionic strength of the solution. Fluorescence spectroscopy experiments confirm the presence of less hydrophilic domains within the aggregates at higher temperatures. The thermoresponsive behavior of the PHPMA-b-POEGMA block copolymers is attributed to the particular solubility characteristics of the hydrophilic, water insoluble PHPMA block that are modulated by the presence of the water soluble POEGMA block.