聚丙交酯立体寡聚物的合成及微结构分析

Synthesis and Microstructure Analysis of Stereoregular Polylactide Oligomers

聚合物物理性质与其主链的立体结构密切相关,精确表征和定量分析聚合物微结构是该领域的重要研究内容之一。以具有确定分子量的立构规整性寡聚物为模型,对其核磁碳谱进行分析,是精确归属聚合物微观结构的关键。以L-丙交酯为起始原料,通过迭代发散/收敛方法,选择苄基和叔丁基二甲基硅基作为一对正交保护基,设计并合成了全同立构的八聚体、十聚体和十二聚体丙交酯寡聚物。通过分析这一系列模型化合物的碳谱,完成了全同聚丙交酯的微结构归属。结果表明:全同立构丙交酯寡聚物的羰基、次甲基和甲基的特征峰分别对应δ169.74、69.15和16.78,并且随着重复单元数的增加,端位基团对寡聚物结构的影响逐渐变小,特征峰向丙交酯聚合物靠近。

The physical properties of polymers are closely related to the stereoscopic structure of their main-chains.Therefore,how to accurately characterize and quantitatively determine polymer microstructure is one of the important research issues in the field.The ^(13)C NMR spectrum analysis of various stereo-oligomers with definite molecular weight is the key to accurately assign the polymer microstructure.In the present contribution,using L-lactide as starting material,the lactide oligomers with 8,10 and 12 degree of polymerization were designed and synthesized by selective divergence/convergence iterative approach,and benzyl and tert-butyldimethylsilyl were selected as a pair of orthogonal protective groups.By analyzing the13C NMR spectra of these model compounds,the microstructure of isotactic polylactide was assigned.It was found that the characteristic peak atδ169.74,69.15 and 16.78 are assigned to carbonyl,methine and methyl of isotactic polylactide,respectively.In addition,with the increase of the number of repeating units,the influence of end groups on the oligomer structure gradually decreases,and the characteristic peak is closer to polylactide.