화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.121, No.12, 2695-2702, 2017
Stereocomplex Crystallization of Linear Two-Armed Stereo Diblock Copolymers: Effects of Chain Directional Change, Coinitiator Moiety, and Terminal Groups
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 Si 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 LID copolymers were largely decreased by Effect A and/or B (both hydroxyl terminal groups).