Copolymerization of 2-Hydroxyethyl Acrylate and 2-Methoxyethyl Acrylate via RAFT: Kinetics and Thermoresponsive Properties

Kinetic studies of the (co)polymerization of 2-hydroxyethyl acrylate (H EA) and/or 2-methoxyethyl acrylate (M EA) via reversible addition fragmentation chain transfer polymerization (RAFT), using dibenzyltrithiocarbonate (DBTTC) as chain-transfer agent, resulting in well-defined copolymers, are presented. Both monomers were found to have equal reactivity revealing the formation of ideal random (azeotropic) copolymers. The thermoresponsive properties of aqueous solutions of the copolymers at 5 mg/ mL, depending on the polymer composition, the chain length, and the end-groups, were investigated. The cloud point (CP) of the synthesized copolymers increases with the content of HEA and decreases with the decreasing chain length. Exchanging one of the hydrophobic benzylic end-groups of the copolymers by isobutyronitrile resulted in more hydrophilic copolymers with significantly higher CP-temperatures. Thus, new potential biomaterials with an adjustable cloud point between 0 and 60 degrees C, showing a small hysteresis between heating and cooling, were successfully prepared.