Stereocomplex Crystallization of Linear Two-Armed Stereo Diblock Copolymers: Effects of Chain Directional Change, Coinitiator Moiety, and Terminal Groups
Stereocomplex Crystallization of Linear Two-Armed Stereo Diblock Copolymers: Effects of Chain Directional Change, Coinitiator Moiety, and Terminal Groups
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线性双臂立体二嵌段共聚物的立体络合物结晶：链方向变化、共引发剂部分和端基的影响
DOI：
10.1021/acs.jpcb.7b00460
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Arakawa Yuki
中科院分区：
文献类型：
--
作者：
Tsuji Hideto;Ogawa Michiaki;Arakawa Yuki
双臂聚乙烯（L-丙交酯）（PLLA）-b-聚合成了具有宽分子量范围的聚（d-丙交酯）（PDLA）（2-LD）共聚物，并研究了共引发剂作为杂质在分子中间引起链方向变化的作用（效果A）和/或端基类型的附加效果（影响B）对2-LD共聚物结晶行为的影响，并与文献报道的单臂PLLA-b B-PDLA（1-LD）共聚物进行了比较。在2-LD和1-LD共聚物中仅形成立体复合物（SC）微晶表明相邻的PLLA和PDLA嵌段促进SC结晶，并且效果A和B都不影响结晶物质。与1-LD共聚物相比，效应A和/或B（均为羟基端基）干扰2-LD共聚物的冷SC结晶。2-LD和1-LD共聚物在冷SC结晶过程中的结晶生长形态分别为球形和固体束，表明结晶生长形态受到效应A和/或B的影响。SC微晶的熔融温度或结晶厚度由每一个嵌段的数均分子量确定，并且不受效果A或B的影响。与1-LD共聚物的球晶的最大径向生长速率相比，2-LD共聚物的球晶的最大径向生长速率被效果A和/或B（均为羟基端基）大大降低。
Two-armed poly(l-lactide) (PLLA)-b-poly(d-lactide) (PDLA) (2-LD) copolymers with a wide-range of molecular weight were synthesized and the effect of coinitiator moiety, which functions as impurity and causes chain directional change in the middle of molecules (Effect A), and/or the additional effect of types of terminal groups (Effect B) on crystallization behavior of 2-LD copolymers were studied, in comparison with that reported for one-armed PLLA-b-PDLA (1-LD) copolymers. Formation of only stereocomplex (SC) crystallites in 2-LD and 1-LD copolymers indicates that neighboring PLLA and PDLA blocks facilitated SC crystallization and neither Effect A nor B affected the crystalline species. Effect A and/or B (both hydroxyl terminal groups) disturbed cold SC crystallization of 2-LD copolymers compared to that of 1-LD copolymers. Crystalline growth morphologies of 2-LD and 1-LD copolymers during cold SC crystallization were spherical and solid sheaf, respectively, exhibiting that crystalline growth morphology was influenced by Effects A and/or B. The melting temperature or crystalline thickness of SC crystallites were determined by number-average molecular weight per one block and not affected by Effect A or B. Maximum radial growth rates of spherulites of 2-LD copolymers compared to those of 1-LD copolymers were largely decreased by Effect A and/or B (both hydroxyl terminal groups).