扩链法制备高分子量聚对二氧环己酮的研究

以辛酸亚锡为催化剂对对二氧环己酮单体(PDO)开环聚合合成聚对二氧环己酮(PPDO),在聚合的后期,用1,6-六亚甲基二异氰酸酯(HDI)为扩链剂进行扩链反应.研究了扩链剂用量对扩链反应的影响,加入相对于PPDO用量的0.78 wt%的HDI就能得到粘均分子量为2.35×105的PPDO.在分子量相近的情况下,扩链后产物的热稳定性和玻璃化转变温度均比未扩链的高,扩链前后的晶型没有发生变化,但结晶度大幅度降低,拉伸性能变化不大.

PREPARATION OF HIGH MOLECULAR WEIGHT POLY(p-DIOXANONE) BY CHAIN-EXTENSION

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.