直接熔融缩聚法合成聚L-乳酸

以L-乳酸为原料,通过直接缩聚法合成了聚L-乳酸(PLLA)。探讨了反应历程中包括聚合温度及时间、催化剂种类及用量对PLLA黏均分子量和光学纯度的影响。采用红外光谱确定聚合物结构,用乌氏黏度计测定黏均分子量,通过旋光仪测定比旋光度,并通过其值计算PLLA的光学纯度。研究表明:合适的聚合温度为150℃,聚合时间为20 h,真空度0.1 MPa,催化剂氯化亚锡和对甲苯磺酸(TSA)组成的复合催化剂效果好于辛酸亚锡、氧化锌;得到的PLLA最高黏均分子量达到41 320,最高光学纯度达到86.4%,可以作为增塑剂使用。

Study on the Synthesis of Poly(L-lactic acid) via Direct Polycondensation

Starting from L-lactic acid,poly（L-lactic acid）（PLLA） was synthesized via direct polycondensation.The factors including polymerization temperature,time,catalysts type and catalyst concentration were discussed.Infrared spectrum was applied to analysis the chemical structure of PLLA,ubbelohde viscosity meter was used to measure the molecular weight of PLLA,and the specific rotation was tested by polarimeter,which can be used to calculate the optical purity of PLLA.Results showed that the optimum reaction conditions were 150 ℃,20 h under 0.1 MPa,SnCl2-TSA with equal mol ratio was the best catalyst of the three catalyst.The PLLA was obtained with a maximum of Mη and optical purity,which was 41 320 and 86.4 %,respectively.The obtained polymer can be applied as the plasticizer.