An Investigation on Phase Behavior of ABA-type Block Copolymers Comprising of 2-Hydroxypropyl Acrylate and Poly (Ethylene Glycol)

ABA-type block copolymers consisting of 2-hydroxypropyl acrylate (HPA) and ethylene glycol (EG) segments were prepared by the RAFT polymerization method using two different lengths of macro-RAFT agents based on commercial poly(ethylene glycol)s with average molar masses of 400 and 1450 gmol-1 (PEG400 and PEG1450). By extending the difunctional ends of PEG400 and PEG1450 vertebrate macro-RAFT agents with HPA units, it was aimed to synthesize three ABA type block copolymers of different lengths from each agent. Structural characterization of the copolymers was performed using FTIR and 1H-NMR spectroscopy. In addition to confirming the chemical structures, signal integrations in the 1H-NMR spectrum provided information about the relative proportions of individual repeating units in each copolymer. Six block copolymers were examined for critical dissolution temperatures based on the relative lengths of the blocks and their PEG content. It was determined that all block copolymer systems examined exhibited lower critical solution temperature (LCST) in the range of 17.2-23.9 oC, and as the ratio of EG units in the copolymers increased, the CST of the copolymers increased.