Synthesis and characterization of poly(ethylene glycol) grafted poly(ε-caprolactone)

A new graft copolymer, poly(epsilon-caprolactone) (PCL) grafted with poly(ethylene glycol) (PEG), was prepared by one-pot synthesis of epsilon-caprolactone and modified PEG. Aluminium isopropoxide or potassium tert-butoxide was used as a catalyst for the ring-opening polymerization. Polymerization using potassium tert-butoxide as a catalyst showed very effective graft reaction of PEG onto poly(epsilon-caprolactone). A slight decrease in the melting temperature was observed with the increase of the PEG graft frequency. Interestingly, considerable changes were observed on the surface property by the introducing PEG side chains compared to that of PCL homopolymer. Measurements of water contact angle showed that the hydrophilic surface of the polymer could be obtained even at a low graft frequency of PEG.