title: Polymorphic Crystallization and Crystalline Reorganization of Poly(l-lactic acid)/Poly(d-lactic acid) Racemic Mixture Influenced by Blending with Poly(vinylidene fluoride).
abstract: The effects of poly(vinylidene fluoride) (PVDF) on the crystallization kinetics, competing formations of homocrystallites (HCs) and stereocomplexes (SCs), polymorphic crystalline structure, and HC-to-SC crystalline reorganization of the poly(l-lactic acid)/poly(d-lactic acid) (PLLA/PDLA) racemic mixture were investigated. Even though the PLLA/PDLA/PVDF blends are immiscible, blending with PVDF enhances the crystallization rate and SC formation of PLLA/PDLA components at different temperatures that are higher or lower than the melting temperature of the PVDF component; it also facilitates the HC-to-SC melt reorganization upon heating. The crystallization rate and degree of SC crystallinity (Xc,SC) of PLLA/PDLA components in nonisothermal crystallization increase after immiscible blending with PVDF. At different isothermal crystallization temperatures, the crystallization half-time of PLLA/PDLA components decreases; its spherulitic growth rate and Xc,SC increase as the mass fraction of PVDF increases from 0 to 0.5 in the presence of either a solidified or a molten PVDF phase. The HCs formed in primary crystallization of PLLA/PDLA components melt and recrystallize into SCs upon heating; the HC-to-SC melt reorganization is promoted after blending with PVDF. We proposed that the PVDF-promoted crystallization, SC formation, and HC-to-SC melt reorganization of PLLA/PDLA components in PLLA/PDLA/PVDF blends stem from the enhanced diffusion ability of PLLA and PDLA chains.
authors.affiliation: State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
authors.forename: Chengtao
authors.initials: C
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Han
authors.affiliation: State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
authors.forename: Jianna
authors.initials: J
authors.lastname: Bao
authors.affiliation: State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
authors.forename: Guorong
authors.initials: G
authors.lastname: Shan
authors.affiliation: State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Bao
authors.affiliation: State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University , 38 Zheda Road, Hangzhou 310027, China.
authors.forename: Pengju
authors.initials: P
authors.lastname: Pan