Synthesis and characterization of ABA type tri-block copolymers derived from p-dioxanone, L-lactide and poly(ethylene glycol)

A series of triblock co-polymers, consisting of a poly(ethylene glycol) (PEG) central block joined to two blocks of random p-dioxanone-co-L-lactide copolymers were synthesized by ring-opening polymerization of p-dioxanone (PDO) and L-lactide (LLA) initiated by PEG in the presence of stannous 2-ethylhexanoate catalyst. The resulting copolymers were characterized by various techniques including 1H and 13C NMR and FTIR spectroscopies, gel permeation chromatography, inherent viscosity, wide-angle X-ray diffractometry (WAXD) and differential scanning calorimetry (DSC). The conversion of PDO and L-lactide into the polymer was studied various mole ratios and at different polymerization temperature from 1H NMR spectra. Results of WAXD and DSC showed that the crystallinity of PEG macroinitiator was greatly influenced by the composition of PDO and L-lactide in the copolymer. The triblock copolymers with low molecular weight were soluble in water at below room temperature. © 2003 Society of Chemical Industry.