RESEARCH ARTICLE
Identification of relaxation processes in pure polyethylene
oxide (PEO) films by the dielectric permittivity and electric
modulus formalisms
Ahmad Telfah
1
|
Mousa M. Abdul‐Gader Jafar
2
|
Inshad Jum'h
3
|
Mais Jamil A. Ahmad
1
|
Jörg Lambert
1
|
Roland Hergenröder
1
1
Leibniz Institut für Analytische
Wissenschaften‐ISAS‐e.V., Bunsen‐Kirchhoff‐
Straße 11, 44139 Dortmund, Germany
2
Department of Physics, Faculty of Science,
The University of Jordan, Amman 11942,
Jordan
3
School of Basic Sciences and Humanities
(SBSH), German‐Jordanian University (GJU),
Amman 11180, Jordan
Correspondence
Ahmad Telfah, Leibniz Institut für Analytische
Wissenschaften‐ISAS‐e.V., Bunsen‐Kirchhoff‐
Straße 11, 44139 Dortmund, Germany.
Email: telfah.ahmad@isas.de
Funding information
Ministerium für Innovation, Wissenschaft und
Forschung des Landes Nordrhein‐Westfalen;
Regierende Bürgermeister von Berlin
Senatskanzlei Wissenschaft und Forschung;
Bundesministerium für Bildung und Forschung
The ac‐impedance of bulk‐like films of pure polyethylene oxide (PEO) polymer was
measured as a function of frequency f in the range 0.1 to 10
7
Hz at various constant
temperatures T (155 − 330 K). The as‐measured data were analyzed by electric permit-
tivity and modulus formalisms to unveil which dielectric and conductive relaxation
processes were responsible for their relaxation behavior below/above glass transition
temperature T
g
of pure PEO polymer. At T > T
g
, none of the α‐, β‐,orγ‐relaxations
could be inferred for studied pure PEO films from frequency variation of measured
imaginary part ε′′(f, T) of complex dielectric permittivity
e
ε f; TðÞ, as low‐frequency
losses masked real dielectric contribution to the measured ε′′(f, T) at low frequencies
and high temperatures. However, at T < T
g
, a broad, relaxation process has been
observed in the high‐frequency part of their isothermal ε′′(f, T) − f spectra, which can
be related to the β‐ or γ‐dielectric relaxation process. Nonlinear regressions of the
measured ε′′(f, T) − f data for T < T
g
yielded moral fits to a simple addition of a
Havriliak‐Negami function, and a Bergman‐loss Kohlrausch‐Williams‐Watts‐type
function, with the relaxation time τ
max
(T) obtained from Havriliak‐Negami‐fitting
parameters, was found to follow a thermally activated Arrhenius‐like relaxation
behavior. Conversely, representation of the imaginary part M′′(f, T > T
g
) − f spectra
of complex electric modulus
e
MfðÞ¼1=
e
ε fðÞwas found to depict 2 overlapped relaxa-
tion processes, which were detached well by a nonlinear regression of a simple super-
position of 2 different M′′(f) expressions having the form of the universal Bergman loss
function, where it was found that the relaxation time is also thermally activated.
KEYWORDS
dielectric functions, electric modulus, impedance spectroscopy, polyethylene oxide (PEO)
1
|
INTRODUCTION
Polyethylene oxide (PEO) polymer fulfills many of the requirements
for solid polymer‐based electrolytes by virtue of its various advanta-
geous physical and chemical properties; thus, it is considered to be a
promising potential candidate as a host medium for inorganic lith-
ium‐ion salts often used in Li‐based and Li‐ion–based electrolyte
batteries.
1-10
Polyethylene oxide is a nontoxic semiconducting polymer of com-
plex molecular structure {H − [O − CH
2
− CH
2
]
n
− OH} with molecular
weight M
w
=18.02 + 44.05n >10
5
g/mol, where n is the number of
repeated molecular chain‐like units of identical monomers. The pure
PEO has melting point T
m
<72
°
C (345 K), crystallization temperature
T
c
≲60
°
C (333 K), and low glass transition temperature T
g
(≳ − 58
°
C ≅ 215 K), depending on its molecular weight, and possesses
strong solvating ability for many metal ions, including Li.
7-16
Besides its
Received: 5 December 2017 Revised: 27 February 2018 Accepted: 28 February 2018
DOI: 10.1002/pat.4306
1974 Copyright © 2018 John Wiley & Sons, Ltd. Polym Adv Technol. 2018;29:1974–1987.wileyonlinelibrary.com/journal/pat
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