链转移剂对D,L-乳酸聚合的影响

The effect of chain transfer agent to synthesis of poly(D, L-)lactides

采用两步法合成了聚D,L-乳酸,即以D,L-乳酸为原料,先制得高纯度聚合单体丙交酯,再以辛酸亚锡为引发剂,月桂醇为链转移剂(即相对分子质量调节剂),高真空条件下开环聚合制得了一系列不同相对分子质量的乳酸均聚物。分别以引发剂用量、链转移剂用量、聚合温度和聚合时间为因素进行正交实验设计,确定了制备较高相对分子质量聚乳酸的反应条件:辛酸亚锡质量分数为0.1%,月桂醇质量分数为0.04%,聚合温度为130℃.聚合时间为10h。在170℃下,考察了链转移剂用量对聚乳酸相对分子质量的影响,得到了聚乳酸相对分子质量与链转移剂用量的定量关系式。用凝胶渗透色谱、红外光谱、核磁共振氢谱等对聚乳酸的结构和性质进行了表征。

Polylactides (PLA) was synthesized by two-step process; firstly, high purity lactide monomer had been prepared from D,L-lactic acid and then, a series of lactide hpmopolymers having different molecular mass had been synthesized with stannous octoate as initiator and lauryl alcohol as chain transfer agent (i.e. regulator for relative molecular mass) via ring-opening polymerization under high vacuum condition. An orthogonal table of experiment was designed, in which dosage of initiator, amount of chain transfer agent, polymerization temperature and reaction time were taken as elements. The reaction conditions for PLA with relatively high molecular mass were determined as follows: mass fraction of stannous octoate 0.1%, mass fraction of lauryl alcohol 0.04%, polymerization temperature 130 ℃ and polymerization time 10 hours. The effect of concentration of chain transfer agent on the relative molecular mass of PLA was studied; a quantitative relation between relative molecular mass of PLA and amount of chain transfer agent was established. The structure and proper ties of PLA were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy and hydrogen spectrum of nuclear magnetic resonance.