聚乳酸的直接缩聚制备及其异氰酸酯扩链探索

Direct Polycondensation Preparation of Poly (L-lactic acid) and Its Diisocyanate Chain-Extention Exploration

通过真空直接缩聚和溶剂回流带水的方法制备了聚L－乳酸，利用真空直接缩聚，在185℃，670Pa的真空下反应18h，产物数均相对分子质量为6700，在常压下以苹甲醇为溶剂在180℃回流36h，产物数均相对分子质量可达19000．上述产物通过1，6-己撑二异氨酸酯（HDI）扩链，数均相对分子质量分别可达31000和63000．经扩链后，产物的相对分子质量分布变宽．辛酸亚锡对扩键反应有明显催化作用．

Poly (L-lactic acid ) having number average Mr 6 700 or 19 000 were obtained by heating at thetemperature of 185 ℃for 18 h under vacuum of 670 Pa, or refluxing with anisole at 180 ℃for 36 h under normal pressure. The number average Mr of these two kinds of poly (lactic acid ) could be increased to 31000 and 63 000 respectively by chain-extending with hexamethylene diisocyanate. The chain-extension broaden the molecular weight distribution of PLA. Stannous octoate may be an effective catalyst for this chain-extending re-action.