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Synthesis of high molecular weight poly( L ‐lactic acid) via melt/solid polycondensation: Intensification of dehydration and oligomerization during melt polycondensation
Author(s) -
Song Fangchao,
Wu Linbo
Publication year - 2011
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.33182
Subject(s) - condensation polymer , dehydration , oligomer , polymerization , polymer chemistry , lactic acid , racemization , lactide , catalysis , chemistry , materials science , organic chemistry , polymer , biochemistry , biology , bacteria , genetics
Melt/solid state polycondensation (MP/SSP) is a cost‐effective route for synthesis of high molecular weight poly( L ‐lactic acid) (PLLA). However, the reaction rates in its four stages need to be enhanced greatly and the reaction times to be shortened largely before the MP/SSP technology can be industrialized. In this study, a new catalyst addition policy, i.e., adding TSA at the dehydration stage and SnCl 2 ·2H 2 O at the MP stage, and more appropriate temperature and pressure programs were presented and applied in the MP process of LLA. The presence of TSA from dehydration appeared very effective for speeding up the dehydration and oligomerization stages as well as depressing racemization in the whole MP process. The polymerization degree ( X n ) of oligomer was clearly increased, and the reaction time was shortened to a great extent. Direct using reduced pressure was also very helpful for intensifying the dehydration stage, only leading to LLA loss as little as 2%. A PLLA with M w of 44,000 and optical purity of 96.8% suitable for subsequent SSP was produced after dehydration for 2 h, oligomerization for 2 h and MP for 4 h under appropriate conditions. And an interesting strong dependence of the M w of final PLLA product on the X n of the oligomer was observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011