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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