Eur. Phys. J. E 4, 173-182
Dielectric relaxation of poly(ethylenglycol)- b-poly(propylenglycol)-b-poly(ethylenglycol) copolymers above the glass transition temperature
S. Moreno1, R.G. Rubio1, G. Luengo2, F. Ortega1 and M.G. Prolongo31 Departamento de Química Física I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
2 L'Oréal, Centre Charles Zviak, Clichy Cedex, France
3 Departamento de Materiales y Producción Aeroespacial, E.T.S.I. Aeronáuticos, Universidad Politécnica, 28040 Madrid, Spain
RGRUBIO@eucmax.sim.ucm.es
(Received: 31 May 2000)
Abstract
The complex dielectric permittivity has been measured
for three
poly(ethylenglycol)-b-poly(propylenglycol)-b-poly(ethylenglycol)
copolymers with different content of poly(ethylenglycol) (15% ,
33% and 80% ), and increasing degree of crystallinity (0% , 10%
and 20% , respectively). Only the non-crystalline sample shows the
normal mode relaxation together with the segmental
(
-relaxation) and the Johari-Goldstein (
-relaxation)
modes. The crystalline samples show also polarization contributions
due to the existence of interfaces between the crystallites and the
amorphous phase. The relaxation times of the ( and normal
modes can be described by a VFT equation with the same value of
T0. There is a slowing-down of the segmental mode due to the
presence of crystallites. The temperature dependence of the
and relaxations in the copolymers is very similar
to that found in pure PPG, while there are significant differences
in the case of the normal mode of the non-crystalline sample. The
size of the cooperatively rearranging regions CRR, and the width of
the glass transition region increase slightly with the degree of
crystallinity. The temperature dependence of the size of CRRs is
compatible with the prediction of fluctuation theory. No systematic
effect of the degree of crystallinity on the -relaxation has
been found. Near 
the -relaxation time is close to
the primitive time of the coupling model.
64.70.Pf - Glass transitions.
77.22.Gm - Dielectric loss and relaxation.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
