紫外光阻隔型低分子量聚乳酸的合成及结构性质研究

Synthesis and Structural Properties of UV-blocking Low MolecularWeight Polylactide

以源于可再生资源的芦荟大黄素(AE)为引发剂,引发丙交酯(LA)开环聚合,合成了具有阻隔紫外光功能的低分子量聚乳酸.系统研究了所合成聚乳酸PLA-En的结构,光学和热学性质.AE分子结构中的醇羟基引发LA聚合形成由En基团(AE分子结构中醇羟基反应后的结构)封端的聚乳酸PLA-En,调控LA与AE之间的摩尔比n(20~200),可调控PLA-En数均分子质量M_(n)(0.29×10^(4)~2.93×10^(4)g/mol);En基团的引入可赋予PLA-En与AE相似的光吸收特征和荧光发射特征,且几乎不受分子量的影响,同时,产物聚乳酸的热稳定性得到提高,PLA-En的热分解温度(T_(d))比由十六醇(CA)引发合成的相近分子量聚乳酸PLA-Cn(Cn为CA结构中醇羟基反应后的结构)高15℃以上,但熔点差别不大.T_(d)的提高赋予PLA-En比PLA-Cn更宽的熔融加工温度窗口,前者超过100℃,后者不超过90℃.将质量比3 mass%的PLA-En(n=20,M_(n)=0.29×10^(4)g/mol)引入商品化聚乳酸PLA(M_(n)=6.28×10^(4)g/mol)中,可赋予PLA较稳定的紫外光阻隔性,但不影响PLA的透明性和力学性能.本文研究结果为后续发展紫外光阻隔的透明聚乳酸材料奠定了很好的基础.

Low molecular weight polylactide with UV resistance was synthesized through ring-opening polymerization of lactide(LA)using aloe-emodin(AE)derived from renewable resources as initiator.The molecular structure,optical properties and thermal properties of the synthesized PLA were systematically studied.The research results show that the alcoholic hydroxyl group in the AE molecular structure initiates the ringopening polymerization of LA to form the polylactide PLA-En capped by the En group(the structure after the reaction of the alcoholic hydroxyl group in the AE structure),the relative number average molecular weight(M_(n))of PLA-En can be tuned(0.29×10^(4)-2.93×10^(4)g/mol)by adjusting the molar ratio n(20-200)between AE and LA;the introduction of En groups can endow PLA-En with similar light absorption and fluorescence emission characteristics to AE,and is hardly affected by molecular weight.At the same time,the thermal stability of obtained polylactide is improved.The thermal decomposition temperature of PLA-En is more than 15℃higher than that of PLA-Cn(Cn is the structure after the reaction of the alcohol hydroxyl group in the CA structure)with similar molecular weight initiated by hexadecanol(CA),but the melting point is not much different.The increase in thermal decomposition temperature endows PLA-En with a wider melt processing temperature window than PLA-Cn,the former exceeds 100℃and the latter does not exceed 90℃.3 mass%of PLA-En(n=20,M_(n)=0.29×10^(4)g/mol)was introduced into commercial polylactide PLA(M_(n)=6.28×10^(4)g/mol),which could endow PLA with UV light blocking properties,but does not affect the transparency and mechanical properties of PLA.The results of this study lay a good foundation to introduce PLA-En into the PLA matrix material and develop a transparent PLA material with UV light protective ability.