Influence of temperature on high molecular weight poly(lactic acid) stereocomplex formation

eXPRESS Polymer Letters

M. Hortos¹ 

关键词: biodegradable polymers;    polylactide;    polymeric racemic mixture;    crystal growing;    capillary rheometry;   

DOI  :  10.3144/expresspolymlett.2019.12

学科分类：生物科学（综合）

来源: eXPRESS Polymer Letters

【 摘 要 】

The influence of temperature on the formation of high molecular weight poly(lactic acid) (PLA) stereocomplexwas studied by evaluation of the precipitates from dioxane solutions of PLA enantiomers (PLLA and PDLA). The racemicmixtures were characterized by Gel Permeation Chromatography, Infrared Spectroscopy, Differential Scanning Calorimetry,Scanning Electronic Microscopy, Wide-Angle X-ray Scattering and Vicat Softening Temperature. Precipitation was carriedout under different solution temperatures, keeping constant the mixing ratio (XD), the molecular weight, the optical purityof both PLA enantiomers and the stirring rate. It was found that the precipitates contained only pure stereocomplex crystallites(racemic crystallites), without observing crystal phase separation between both homocrystals. The kinetics of the insolublephase formation could be adjusted with the Avrami model, classically used for polymer crystallization in molten state. Itwas observed that the maximum PLA stereocomplex production rate was at about 40 °C. However, more thermally stableracemic crystallites were formed at high solution temperatures. It was found that all the precipitates were sphere-like at10 g·dl–1 at the solution temperature of 25, 40, 60 and 80 °C.

【 授权许可】

CC BY