苯基-低聚倍半硅氧烷和氨基-低聚倍半硅氧烷对左旋聚乳酸结晶行为及热稳定性的影响

以二氯甲烷为溶剂，将不同相对分子质量的左旋聚乳酸（PLLA）与笼型多面体低聚倍半硅氧烷（POSS）进行溶液共混制备POSS/PLLA复合材料。并通过热台偏光显微镜（POM）、DSC、XRD和TGA对POSS/PLLA复合材料和PLLA的结晶形貌、结晶性能和热稳定性进行了表征。结果表明：POSS/PLLA复合材料的结晶温度升高到110℃左右，结晶能力提高；初始热分解温度和终止热分解温度均增大，最大热分解速率对应的温度在373~379℃之间，热稳定性提高。另外，当POSS含量较低时，成核作用占主导地位；而POSS含量较高时，POSS对PLLA分子链运动的阻碍作用逐渐增强。且POSS的阻碍作用对相对分子质量高的PLLA更明显。观察POSS/PLLA复合材料和PLLA的等温结晶形貌，可以看出明显的十字消光现象和环带球晶形貌，另外，球晶在降温过程中会产生裂纹，这与PLLA的脆性有关。

Effect of phenyl-polyhedral oligomeric silsesquioxane and amino-polyhedral oligomeric silsesquioxane on crystallization behavior and thermal stability of ploy(L-Lactic acid)

Polyhedral oligomeric silsesquioxane/ploy (L-Lactic acid) (POSS/PLLA) composites were prepared by blending POSS and PLLA with different molecular mass in dichloromethane solvent. The crystallization morphology, crystallization behavior and thermal properties of POSS/PLLA composites were studied by polarizing microscope (POM), DSC, XRD and TGA. The results show that the crystallization temperatures of POSS/PLLA composites increase to about 110℃ and their crystallization ability increases. The initial thermal decomposition temperature and the terminate thermal decomposition temperature of the POSS/PLLA composites increase and the temperature corresponding to the maximum decomposition rate is between 373℃ and 379℃, which indicates that their thermal stability is improved. When the content of POSS is lower, the nucleation plays a dominant role. When the content of POSS is higher, it hinders the movement of PLLA chains. And the blocking effect of POSS is stronger for high molecular weight PLLA. The cross extinction phenomenon and the ring band crystal morphology appear in POSS/PLLA composites and PLLA are seen obviously during isothermal crystalization. The spherulite in the cooling process produces cracks, which is related to the brittleness of PLLA.