Effect of Environmental Humidity on the Ionic Transport of Poly(ethylene Oxide) Thin Films by Local Dielectric Spectroscopy
In this work, we study the effect of humidity on the ionic transport in the amorphous phase of poly(ethylene oxide) thin films via local dielectric spectroscopy measurements. We explored a controlled humidity range between 15 %RH and 50 %RH. AFM-based local dielectric imaging allowed us to obtain the thin films topography and dielectric contrast maps, simultaneously. No humidity effect on the film topography was observed whereas large variation of the dielectric signal occurred. In addition, we observed a clear dielectric contrast among different locations on the thin film surface. In two selected regions with high contrast in the dielectric maps, we performed nanoDielectric Spectroscopy (nDS) measurements covering the range from 10 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 were extracted being about 36%, independently of humidity conditions. On the contrary, the average conductivity increased drastically from 2 10-10 to 5 10-9 S/cm, by changing environmental humidity in the explore %RH range.