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Experimental (IR/Raman and 1H/13C NMR) and Theoretical (DFT) Studies of the Preferential Conformations Adopted by l-Lactic Acid Oligomers and Poly(l-lactic acid) Homopolymer

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journal contribution
posted on 12.01.2012, 00:00 by S. Jarmelo, D. A. S. Marques, P. N. Simões, R. A. Carvalho, C. M. S. G. Batista, C. Araujo-Andrade, M. H. Gil, R. Fausto
l-Lactic acid (l-LA) oligomers (up to the pentamer) were studied by three complementary approaches: vibrational (IR and Raman) and NMR (1H and 13C) spectroscopies and DFT calculations. Vibrational and NMR spectra of l-LA oligomers and poly(l-lactic acid) (PLLA) homopolymer were recorded at room temperature and interpreted. Further insight into the structures (conformations) of the title systems was provided by theoretical B3LYP/6-311++G(d,p) studies. Calculated energies and computed vibrational and NMR spectra of the most stable conformers of l-LA oligomers, together with the experimental vibrational and NMR spectra, enabled the characterization of the preferred conformations adopted by PLLA chains.