摘要
在超临界二氧化碳流体中用辛酸亚锡作催化剂，用左旋丙交酯开环聚合成功地合成了相对分子质量大于80000，分散指数为2．5的聚左旋乳酸。深入研究了聚合温度、时间、压力、单体浓度、催化剂用量及超临界二氧化碳纯度等各种因素对聚左旋乳酸相对分子质量及其分布的影响，对聚合物的相对分子质量和分布采用凝胶渗析色谱、^1H NMR谱、^13C NMR谱、红外光谱和差式扫描量热器等进行表征。结果表明：聚合温度、单体对催化剂的浓度比和超临界二氧化碳纯度是关键因素，最佳聚合条件为温度85—90℃，c（LA）／c（SnOct2）为500—1000，聚合时间48h；辛酸亚锡是高效催化剂，但催化效率随影响因素而变；超临界二氧化碳流体中的聚合机理为配位插入聚合。
Poly（L-lactides） with relatively high relative molecular mass, mass-average relative molecular mass more than 80 000 with polydispersity index （PDI） 2.5 measured by gel permeation chromatography, is successfully synthesized by ring-opening polymerization of L-lactides in supercritical carbon dioxide using stannous octoate as initiator. Various effects such as polymerization temperature, time,pressure, concentrations of monomer and catalyst, and purity of SC-CO2 on relative molecular mass of PLLA and relative molecular mass distribution as well as monomer conversion monitored with ^1H NMR spectroscopy are systematically investigated. It is found that polymerization temperature, monomer to catalyst molar ratio, and purity of carbon dioxide are the key factors. The catalysis efficiency indicates that one SnOct2 molecule is able to initiate a number of polymer chhins, which is varied with all effects. The experimental results are consistent with the coordination-insertion polymerization mechanism in which stannous alkoxide initiator is formed in situ via reaction between stannous octoate and traces of water present in carbon dioxide and catalyst. The resulting polymer is also characterized with ^13C NMR,FT-IR and DSC.
出处
《后勤工程学院学报》
2011年第6期41-51,共11页
Journal of Logistical Engineering University
基金
the Academic Innovative Project of Logistical Engineering University for the financial support to this project(YZ07-43501)
关键词
超临界二氧化碳
开环聚合
聚L-丙交酯
催化效率
辛酸亚锡
聚合机理
凝胶渗析色谱
supercritical CO2
ring-opening polymerization
poly （L-lactide）
catalysis efficiency
stannous octoate
polymerization mechanism
gel permeation chromatography
