About the transformation of low into high poly(-lactide)s by annealing under the influence of transesterification catalysts
Cyclic polylactides were prepared in bulk at 170 °C, crystallized at 120 °C and then annealed at temperatures between 130 and 170 °C with variation of catalyst, catalyst concentration and annealing time. The transformation of the initially formed low melting (L T m ) crystallites, having melting tem...
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Published in | RSC advances Vol. 11; no. 5; pp. 2872 - 2883 |
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Main Authors | , , , |
Format | Journal Article |
Published |
12.01.2021
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Online Access | Get full text |
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Summary: | Cyclic polylactides were prepared in bulk at 170 °C, crystallized at 120 °C and then annealed at temperatures between 130 and 170 °C with variation of catalyst, catalyst concentration and annealing time. The transformation of the initially formed low melting (L
T
m
) crystallites, having melting temperatures (
T
m
) < 180 °C into high melting (H
T
m
) crystallites having
T
m
values > 189 °C was monitored by means of DSC measurements and characterized in selected cases by SAXS measurements. It was confirmed that the formation of H
T
m
crystallites involves a significant growth of the thickness of the lamellar crystallites along with smoothing of their surface. Annealing at 170 °C for 1 d or longer causes thermal degradation with lowering of the molecular weights, a gradual transition of cyclic into linear chains and a moderate decrease of lamellar thickness. An unexpected result revealed by MALDI TOF mass spectrometry is a partial reorganization of the molecular weight distribution driven by a gain of crystallization enthalpy.
Cyclic polylactides were prepared in bulk at 170 °C, crystallized at 120 °C and then annealed at temperatures between 130 and 170 °C with variation of catalyst, catalyst concentration and annealing time. |
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Bibliography: | 10.1039/d0ra10012a Electronic supplementary information (ESI) available. See DOI |
ISSN: | 2046-2069 |
DOI: | 10.1039/d0ra10012a |