@article {18141, title = {Confinement Effects on the Dynamic Behavior of Poly(D,L-lactic Acid) upon Incorporation in α-Cyclodextrin}, journal = {J Phys Chem B}, volume = {118}, year = {2014}, month = {2014-09-01 00:00:00}, pages = {6972-6981}, publisher = {ACS}, abstract = {

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 {\textdegree}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.

}, keywords = {Inclusion complexes, PDLLA}, author = {Viciosa, M. T. and Alves, N. M. and Oliveira, T. and Dionisio, M. and Mano, J. F.} }