Eur. Phys. J. E 8, 167-173 (2002)
DOI: 10.1140/epje/i2001-10090-x
Confinement-induced differences between dielectric normal modes and segmental modes of an ion-conducting polymer
K. Kojio, S. Jeon and S. GranickDepartment of Materials Science & Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA sgranick@uiuc.edu
(Received 31 August 2001 and Received in final form 30 October 2001)
Abstract
Dielectric measurement in the range 0.1 Hz to 1 MHz were used to study the
motions of polymers and ions in an ion-conducting polymer, polypropylene
oxide containing small quantities (on the order of 1%) of lithium ions
(LiClO
4), confined as a sandwich of uniform thickness between
parallel insulating mica surfaces. In the dielectric loss spectrum, we
observed three peaks; they originated from the normal mode of the polymer,
segmental mode of the polymer, and ion motions. With decreasing film
thickness, the peak frequencies corresponding to the normal mode and ion
motion shifted to lower frequencies, indicating retardation due to
confinement above 30 nm. This was accompanied by diminished intensity of the
dielectric normal-mode relaxation, suggesting that confinement diminished
the fluctuations of the end-to-end vector of the chain dipole in the
direction between the confining surfaces. On the contrary, the segmental
mode was not affected at that thickness. Finally, significant retardation of the
segmental mode was observed only for the thinnest film (14 nm). The different
dynamical modes of the polymer (segmental and slowest normal modes) respond
with different thickness and temperature dependence to confinement.
82.35.Gh - Polymers on surfaces; adhesion.
61.25.Hq - Macromolecular and polymer solutions; polymer melts; swelling.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002