High molecular weight biodegradable poly（ether ester）

poly（p-dioxanone）（PPDO）

has been prepared by chain-extending from its prepolymer using hexamethylene diisocyanate（HDI） as a chain extender.The ring-opening polymerization of p-dioxanone（PDO） using stannous octoate（SnOct

2

） as a catalyst was conducted at 125℃ for 3 h

and then a certain amount of HDI was added into the reactive system to react with the resulting PPDO prepolymer for an additional 30 min.The effect of the weight ratio of HDI to PPDO on the molecular weight of the chain-extended PPDO has been studied

and the results show that when the ratio is 0.78 wt%

higher molecular weight PPDO can be obtained

demonstrating that HDI is an effective extender for PPDO.The thermal degradation behaviors of PPDO and chain-extended polymer（PPDO-HDI） in air have been investigated by TG.The results show that the thermal stability of PPDO-HDI is higher than that of PPDO.Differntial scanning calorimetry（DSC） and wide angle X-ray diffractometry（WXRD） have been utilized to investigate the crystallization behavior of PPDO-HDI and PPDO.There exists no obvious difference between the crystal structures of PPDO-HDI and PPDO

however

the crystallinity of PPDO-HDI decreases to 33% from 60% of PPDO;the melting point of PPDO-HDI decreases a little and its glass transition temperature increases compared with those of PPDO.Moreover

the tensile strength and the elongation at break of PPDO-HDI are 36 MPa and 464%

respectively

almost the same as those of PPDO.