Journal Article

FZJ-2016-02462

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Dielectric relaxations of nanocomposites composed of HEUR polymers and magnetite nanoparticles

Campanella, A. (Corresponding author) ; Brás, A. ; Raftopoulos, K. N. ; Papadakis, C. M. ; Vassiliadou, O. ; Kyritsis, A. ; Appavou, M. S.FZJ* ; Müller-Buschbaum, P. ; Frielinghaus, H.FZJ*

2016
Elsevier Science Oxford

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Please use a persistent id in citations: http://hdl.handle.net/2128/12285  doi:10.1016/j.polymer.2016.04.045

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.

Keyword(s): Polymers, Soft Nano Particles and Proteins (1st) ; Soft Condensed Matter (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)
2. Neutronenstreuung (Neutronenstreuung ; JCNS-1)

Research Program(s):

1. 6G15 - FRM II / MLZ (POF3-6G15) (POF3-6G15)
2. 6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623) (POF3-623)
3. 6215 - Soft Matter, Health and Life Sciences (POF3-621) (POF3-621)

Experiment(s):

1. TEM-MLZ: Transmission electron microscope at MLZ

Appears in the scientific report 2016

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Database coverage:
; ; Current Contents - Physical, Chemical and Earth Sciences ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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