Stereocomplex Crystallization of Star-Shaped Four-Armed Stereo Diblock Poly(lactide) from the Melt: Effects of Incorporated Linear One-Armed Poly(l‑lactide) or Poly(d‑lactide)

• Published in: The journal of physical chemistry. B Vol. 121; no. 42; pp. 9936 - 9946
• Main Authors: Tsuji, Hideto, Ozawa, Ryota, Arakawa, Yuki
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 26.10.2017
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/acs.jpcb.7b07420

Star-shaped four-armed stereo diblock poly­(lactide) (4-LD) and linear one-armed PLLA or PDLA (1-L or 1-D) having a molecular weight similar to that of 4-LD [higher molecular weight 1-L­(H) or 1-D­(H)] and that of one block of 4-LD [lower molecular weight 1-L­(L) or 1-D­(L)] were synthesized, and the effects of incorporated 1-L or 1-D on the isothermal and nonisothermal crystallization of 4-LD blends from the melt were investigated. Solely stereocomplex crystallites were formed in unblended 4-LD and 4-LD blends incorporated with 1-L or 1-D during isothermal and nonisothermal crystallization. Incorporated 1-L or 1-D increased normalized stereocomplex crystallinity and accelerated cold nonisothermal crystallization and isothermal crystallization. The accelerating effect became higher with decreasing the molecular weight of 1-L or 1-D. The crystalline growth mechanism was not altered by the incorporation of 1-L and 1-D, whereas the crystalline growth geometry changed from line to sphere or circle, depending on the type of sample and T c. The difference in crystallization half time and cold crystallization temperature between 4-LD/1-L­(H) and 4-LD/1-D­(H) blends or 4-LD/1-L­(L) and 4-LD/1-D­(L) blends was explained by the difference in radial growth rate and spherulite density, which was further discussed considering the non-interpenetrating and interpenetrating models.