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@ARTICLE{Campanella:808950,
author = {Campanella, Antonella and Brás, A. and Raftopoulos, K. N.
and Papadakis, C. M. and Vassiliadou, O. and Kyritsis, A.
and Appavou, M. S. and Müller-Buschbaum, P. and
Frielinghaus, H.},
title = {{D}ielectric relaxations of nanocomposites composed of
{HEUR} polymers and magnetite nanoparticles},
journal = {Polymer},
volume = {96},
issn = {0032-3861},
address = {Oxford},
publisher = {Elsevier Science},
reportid = {FZJ-2016-02462},
pages = {70-80},
year = {2016},
abstract = {We investigate the dynamics of nanocomposites composed of
hydrophobically modified ethoxylated urethanes (HEUR) and
magnetite nanoparticles (MNPs) as dry films. Weemployed
dielectric relaxation spectroscopy (DRS) in combination with
differential scanning calorimetry (DSC) and thermally
stimulated depolarization currents (TSDC).The three
techniques reveal a strong heterogeneity of the matrix of
the nanocomposites, consisting of (i) a crystalline
poly(ethyleneoxide) PEO bulk phase, (ii) an amorphous PEO
portion, and (iii) small PEO crystallites which experience
different constraints than the PEO bulk phase. TSDC and DRS
reveal a very high direct current (DC)-conductivity of the
pure matrix, which increases with MNPs concentration. The
increase of the DCconductivity is not related to an increase
of the segmental mobility, but most likely to the change of
the morphology of the hydrophobic domains of the polymer
matrix, due to the formation of large MNPs clusters. Indeed,
the MNPs neither influence the segmental dynamics of the
polymer nor the phase behavior of the polymer matrix. The
addition of MNPs slightly increases the activation energy
related to the γ-relaxation of the polymer. This effect
might be related to the changes in nano-morphology as
demonstrated by the slight increase of the degree of
crystallinity. The analysis of the DRS data with the
electrical modulus M’’(ω) and the derivative
ε’’der formalism allow us to identify a low-frequency
process in addition to the conductivity relaxation. This
low-frequency dispersion is also revealed by TSDC. It is
most likely related to the Maxwell-Wagner- Sillars
relaxation, which typically occurs in systems which feature
phase separation. The detailed investigation of the
dielectric properties of these novel nanocomposites with
increasing MNPs concentration will be useful for their
practical application, for example as absorbers of
electromagnetic waves.},
cin = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
(München) ; JCNS-FRM-II / Neutronenstreuung ; JCNS-1},
ddc = {540},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-1-20110106},
pnm = {6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
Neutron Research (JCNS) (POF3-623) / 6215 - Soft Matter,
Health and Life Sciences (POF3-621)},
pid = {G:(DE-HGF)POF3-6G15 / G:(DE-HGF)POF3-6G4 /
G:(DE-HGF)POF3-6215},
experiment = {EXP:(DE-MLZ)TEM-MLZ-20151210},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000376728300010},
doi = {10.1016/j.polymer.2016.04.045},
url = {https://juser.fz-juelich.de/record/808950},
}