Synthesis and properties of crystalline dicarboxylated poly(L-lactic acid) prepolymers

Authors

  • Xiangying Sun,

    1. Department of Chemical & Biological Engineering, State Key Laboratory of Chemical Engineering, Zhejiang University, Hangzhou 310027, China
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  • Linbo Wu

    Corresponding author
    1. Department of Chemical & Biological Engineering, State Key Laboratory of Chemical Engineering, Zhejiang University, Hangzhou 310027, China
    • Department of Chemical & Biological Engineering, State Key Laboratory of Chemical Engineering, Zhejiang University, Hangzhou 310027, China===

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Abstract

Crystalline 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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