不同溶劑處理效應對左旋聚乳酸結晶行為的影響

Abstract

本研究探討在不同溶劑處理效應下，左旋聚乳酸(PLLA)分子鏈的構型(conformation)對結晶動力學的影響。 利用PLLA溶液狀態下時，不同的溶劑對PLLA有著不同的作用力，使得PLLA在溶液中的分子鏈型態不同，有了不同的熱力學平衡狀態。因此由氯仿與四氫夫喃溶解後的PLLA兩者相比，使得經由不良溶劑(四氫夫喃)溶解過的PLLA其分子鏈構型gtt存在比例增加。因為分子鏈比例的不同使得PLLA的結晶速率、結晶誘導時間以及晶核密度等等而有所不同。我們預測不同溶劑處理過PLLA後，會造成高分子鏈構型的不同而對PLLA結晶行為有所影響。因此利用POM、DSC、XRD等儀器觀察其因溶劑效應帶來的結晶行為之改變，找出結晶動力學模式與熱力學參數間的關係後，發現分子鏈構型gtt的存在比例變多，提升了分子鏈的成核能力，進而影響PLLA的α與α結構存在共存區的結晶動力學。

Influence of chain conformation on crystallization kinectics of Poly L-lactide been dissolved in different solvent was studied in the research. The increase of population of gtt chain conformers which changes the equilibrium state on thermodynamic; Furthermore, the crystallization rate, the induction time and the nucleus density are also changing. Using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction to observe the crystallization behavior of oriented amorphous PLLA, we connected the relation between crystallization kinetics model and thermodynamic parameters. We found that increasing the population of gtt comformer before crystallization improves the nucleation ability of PLLA and finally changes the crystallization kinetics at the temperature α and α' coexist.