Effect of environmental humidity on the ionic transport of poly(ethylene oxide) thin films by local dielectric spectroscopy
Soft Matter 16(13) : 3203-3208 (2020)
Abstract
The effect of humidity on the ionic transport in the amorphous phase of poly(ethylene
oxide) thin films has been studied by via local dielectric spectroscopy. We explored a
controlled humidity range between 15 %RH and 50 %RH. AFM-based local dielectric
imaging allowed to obtain simultaneously the thin films topography and the
corresponding dielectric contrast maps. No humidity effect on the film topography was
observed whereas large variation of the dielectric signal could be detected. In addition,
we observed a clear dielectric contrast in different locations on the thin film surface. At
selected regions with high contrast in the dielectric maps, we performed nanoDielectric
Spectroscopy (nDS) measurements covering the frequency range from 5 Hz to 100 kHz.
By modeling these spectroscopy results, we quantified the conductivity of the
amorphous phase of the semicrystalline poly(ethylene oxide) films. The crystalline
fraction of the PEO thin films was extracted and found to be about 36%, independently
of humidity. However, the average conductivity increased by a factor of 25 from 2×10-
10 to 5×10-9 S/cm, by changing environmental humidity in the explored %RH range.