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TitleConfinement effects on the dynamic behavior of poly(d,l‑lactic acid) upon incorporation in α‑cyclodextrin
Author(s)Viciosa, M. T.
Alves, N. M.
Oliveira, T.
Dionísio, M.
Mano, J. F.
KeywordsInclusion complexes
Issue dateSep-2014
PublisherACS Publications
JournalThe Journal of Physical Chemistry
CitationViciosa M. T., Alves N. M., Oliveira T., Dionisio M., Mano J. F. Confinement Effects on the Dynamic Behavior of Poly(D,L‑lactic Acid) upon Incorporation in α‑Cyclodextrin, J Phys Chem B, Vol. 118, pp. 6972-6981, 2014
Abstract(s)Inclusion complexes (ICs) composed of α-cyclodextrin (α-CD) and poly(D,L-lactic acid) (PDLLA), with 10/24 (IC1) and 15/46 (IC2) (% w/ w) of PDLLA incorporated/initial PDLLA weight percentage, were prepared and characterized mainly by dielectric relaxation spectroscopy (DRS). Bulk PDLLA was also analyzed for comparison. DRS was revealed to be a suitable tool to distinguish the dynamical response of the PDLLA regions constrained in between α-CD channels from the fraction incorporated inside channels. While the cooperative α-process undergoes a dramatic depletion shifting to higher temperatures (∼4.5 °C) for the PDLLA interchannels portion, it is suppressed for PDLLA chains inside pores. It was demonstrated that the broad secondary relaxation of bulk PDLLA is the Johari−Goldstein process (βJGprocess). The detection of its analogue in the ICs at higher frequencies, to a greater extent in IC1, is interpreted as a true confinement effect where the dimensions of the α-CD channels interfere with the length scale of the βJG-process. The limit predicted in the framework of the coupling model, where the α-relaxation transforms in the βJG-process, seems to be reached in the ICs. Furthermore, it was found that the length scale of the additional γ process only detected in the ICs is inferior to inter- or intrachannel dimensions.
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Appears in Collections:3B’s - Artigos em revistas/Papers in scientific journals

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