Two kinds of PCL/PEO/PLA tri-component copolymers(PCEL) with different composition were synthesized by direct copolymerization of ε caprolactone

L-lactide and PEG(6000) in the presence of stannous octoacte at 130℃ for 56h.The biodegradation behavior of these copolymers was investigated in a pH7 4 phosphate buffer solution at 37±1℃ in vitro.The changes of water sorption

loss weight

molecular weight

molecular weight distribution

thermal properties and composition of the copolymer were monitored by GPC

DSC

XRD and 1H-HMR techniques.The results showed that the hydrophilicity of the copolymer was enhanced with increasing PEO content

which lead to decrease of the PEO component and increase of the loss weight of the copolymer with degradation time. It was considered that the obtained bi-modal chromatogram of the GPC profile was attributed to the degradation of the partial crystalline polymer.Since degradation has taken in priorty in amorphous zones and at the edges of crystalline of the polymer

bi-modal molecular weight distribution of GPC spectrum was formed.This interpretation was supported by DSC and X-ray diffraction data.