Abstract
AbstractCrystalline dicarboxylated poly(L‐lactic acid)s (dcPLLAs) with number‐average molecular weights (Mn's) of 103 to 104 g/mol were synthesized via the melt polycondensation of L‐lactic acid (LLA) in the presence of succinic anhydride (SAD), with tin(II) chloride and toluene‐4‐sulfonic acid as binary catalysts. They were characterized by end‐group titration, 1H‐NMR, differential scanning calorimetry, and wide‐angle X‐ray diffraction. The terminal COOH percentage reached over 98%, and the molecular weight could be controlled by the molar ratio of LLA to SAD. The thermal behaviors depended on the molecular weight. The poly(L‐lactic acid)s (PLLAs) crystallized slowly for Mn ≤ 2000 but quickly for Mn ≥ 4000. The crystallinity increased from 27 to 40% when Mn grew from 4000 to 10,000. With comparison to ordinary PLLA, the dcPLLA had the same crystallization structure but a slightly lower crystallizability. The glass‐transition temperature was clearly higher than that of amorphous dcPLLAs. With a controllable molecular weight, high COOH percentage, and crystallinity, the dcPLLA with Mn ≥ 4000 appeared to be a suitable prepolymer for the preparation of high‐molecular‐weight crystalline PLLA via chain extension. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
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