SYNTHESIS AND CHARACTERIZATION OF POLY(EPSILON-CAPROLACTONE) - POLY(ETHYLENE GLYCOL) BLOCK-COPOLYMER

Poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolac tone) triblock copolymers (PECL) covering a wide range of poly( ethyle ne glycol) (PEG) lengths were synthesized with alkali metal alkoxide d erivatives of poly(ethylene glycol). The effects of various factors, s uch as amount of the initiator, reaction time and temperature, polarit y of solvent, length of PEG segment, and counterion on the polymerizat ion were investigated. The copolymers were characterized by H-1-NEVIR, IR, GPC, and DSC. It was found that THF system is superior to toluene system. The conversion of the monomer increased with increase of the initiator concentration. High molecular weight of the copolymer and hi gh conversion of the monomer was obtained at below 30 degrees C within 5 min. The polymerization process was studied by GPC and the coexiste nce of propagation and transesterification reaction was found, which l eaded to relatively broad molecular weight distribution of the copolym ers. (C) 1997 John Wiley & Sons, Inc.