Promoted Stereocomplex Crystallization in Supramolecular Stereoblock Copolymers of Enantiomeric Poly(Lactic Acid)s

Abstract

Telechelic and 3-arm star-shaped poly(l-lactic acid)s (PLLAs) and poly(d-lactic acid)s (PDLAs) end-functionalized by 2-ureido-4[1H]-pyrimidione (UPy) self-complementary quadruple hydrogen-bonding motifs were synthesized by terminally modifying the corresponding hydroxyl-terminated polymers. The PLLA/PDLA stereoblock supramolecular polymers (sb-SMPs) with linear and branched architectures were further prepared by mixing the UPy end-functionalized telechelic, 3-arm star-shaped PLLA and PDLA through the dimerization of UPy groups, as verified by viscometry. Crystallization kinetics, polymorphic crystalline structure, and lamellae morphology of the PLLA/PDLA sb-SMPs were investigated and compared with the corresponding blends without UPy end functionalities. Compared to the PLLA/PDLA blends, the sb-SMPs exhibit higher crystallization rate and prefer to crystallizing into the high-melting-point stereocomplex (sc), rather than the low-melting-point homocrystallite in both the nonisothermal and isothermal crysta...