Study of novel biodegradable thermo-sensitive hydrogels of methoxy-poly(ethylene glycol)-block-polyester diblock copolymers

A series of biodegradable thermo-sensitive hydrogels were synthesized by ring-opening polymerization of methoxy-poly(ethylene glycol) (mPEG) and various ester monomers, i.e. D,L-lactide, glycolide, β-propiolactone, δ-valerolactone and e-caprolactone. The copolymers were characterized using 1H NMR spectroscopy and gel permeation chromatography. The micelle properties were also measured. The results indicated that the diblock copolymers formed nano-micelles at low concentrations in aqueous phase. The lower critical solution temperatures of the diblock copolymers were above 35 °C at 1 wt%. As the temperature increased above room temperature, the diblock copolymer solutions underwent a sol-to-gel phase transition, which was manifested in viscosity increases, indicative of the formation of a gel. The mPEG–polyester diblock copolymer solutions exhibited sol-gel transition behavior as a function of temperature and polymer concentration. Copyright © 2010 Society of Chemical Industry