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Morphology, conformation and configuration of a series of aliphatic polyesters of the polylactide-type were studied by 13 C n.m.r. and vibrational spectroscopies. Investigations were performed on the stereocomplex (PLAcomplex) formed by cocrystallisation of poly(L-lactic acid) and poly(D-lactic acid), on poly(D,L-lactic acid) and on poly( meso -lactide) stereocopolymers. Comparison was made with poly(L-lactic acid) PLA100, taken as a reference. Fundamental vibrations were correlated to bands characterising morphology, conformation and configuration of these different polymers. Factor group analysis based on the 10 3 and 3 1 helical conformations of semi-crystalline PLA100 and PLAcomplex, respectively, led to good agreement with information collected from X-ray diffraction. It was further shown that difference in tacticity between amorphous ‘preferentially isotactic’ poly(D,L-lactic acid) and ‘preferentially syndiotactic’ poly( meso -lactide) can be detected from the vibrational position of δCH and symmetric δCH 3 bending modes. Solid state 13 C n.m.r. confirmed the different conformations of semi-crystalline PLA100 and PLAcomplex, but did not allow us to discriminate the different tacticities of the amorphous stereocopolymers, contrary to Raman spectroscopy. © 1997 Elsevier Science Ltd. |
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