Suganuma, Koto Teijin
Asakura, Tetsuo Tokyo University of Agriculture and Technology
押村, 美幸 Tokushima University 徳島大学 教育研究者総覧 KAKEN研究者をさがす
平野, 朋広 Tokushima University 徳島大学 教育研究者総覧 KAKEN研究者をさがす
右手, 浩一 Tokushima University 徳島大学 教育研究者総覧 KAKEN研究者をさがす
Cheng, H. N. USDA Agricultural Research Service
The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, and its polymer stereochemistry can be effectively studied by NMR spectroscopy. In previously published NMR studies of PLA tacticity, the NMR data were fitted to pair-addition Bernoullian models. In this work, we prepared several PLA samples with a tin catalyst at different L,L-lactide and D,D-lactide ratios. Upon analysis of the tetrad intensities with the pair-addition Bernoullian model, we found substantial deviations between observed and calculated intensities due to the presence of transesterification and racemization during the polymerization processes. We formulated a two-state (pair-addition Bernoullian and single-addition Bernoullian) model, and it gave a better fit to the observed data. The use of the two-state model provides a quantitative measure of the extent of transesterification and racemization, and potentially yields useful information on the polymerization mechanism.
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