Fractionated Crystallization Kinetics and Polymorphic Homocrystalline Structure of Poly(_(L)-lactic acid)/Poly(_(D)-lactic acid)Blends:Effect of Blend Ratio  

作　　者：Wang-Kai Xiang Qing Xie Shan-Shan Xu Chen-Xuan Sun Cheng-Tao Yu Ying Zheng Peng-Ju Pan 

机构地区：[1]State Key Laboratory of Chemical Engineering,College of Chemical and Biological Engineering,Zhejiang University,Hangzhou 310027,China [2]Institute of Zhejiang University-Quzhou,Quzhou 324000,China

出　　处：《Chinese Journal of Polymer Science》2022年第6期567-575,共9页高分子科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(No.21873083).

摘　　要：Stereocomplex(SC)crystallization has been an effective way to improve the physical performances of stereoregular polymers.However,the competition between homo and SC crystallizations can lead to more complicated crystallization kinetics and polymorphic crystalline structure in stereocomplexable polymers,which influences the physical properties of obtained materials.Herein,we select the medium-molecular-weight(MMW)poly(L-lactic acid)/poly(D-lactic acid)(PLLA/PDLA)asymmetric blends with different PDLA fractions(f_(D)=0.01-0.5)as the model system and investigate the effects of f_(D) and crystallization temperature(T_(c))on the crystallization kinetics and polymorphic crystalline structure.We observe the fractionated(i.e.,multistep)crystallization kinetics and the formation of peculiar β-form homocrystals(HCs)in the asymmetric blends under quiescent conditions,which are strongly influenced by both f_(D) and T_(c).Precisely,crystallization of β-form HCs is favorable in the MMW PLLA/PDLA blends with high f_(D)(≥0.2)at a low T_(c)(80-100℃).It is proposed that the formation of metastable β-form HCs is attributed to the conformational matching between β-form HCs and SCs,and the stronger constrain effects of precedingly-formed SCs in the early stage of crystallization.Such effects can also cause the multistep crystallization kinetics of MMW PLLA/PDLA asymmetric blends in the heating process.

关 键 词：Poly(lactic acid) Stereocomplex crystallization Polymorphic structure Crystallization kinetics 

分 类 号：TQ317[化学工程—高聚物工业]