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Study of (PEO)8ZnCl2 polymer electrolytes via SAXS and DSC techniques

Nanocomposite polymer electrolytes are coming to the focus of interests of scientists as it is expected them to be applied in construction of nanostructured solar cells and in the second generation of galvanic cells. Their electrical properties can be considerably improved by crosslinking. Thus the amorphous phase, which is more conductive than crystalline phase of polymer, can be enhanced. Primary poly(ethylene-oxide), PEO was crosslinked by g-irradiation of 60Co till doses of 309 KGy and used in preparation of (PEO)8ZnCl2 polymer electrolyte films with and without addition of nano-particles of TiO2. Electrical, thermical and optical properties of the polymer electrolytes were determined and as well as IR spectra were measured. With the irradiation dose conductivity abruptly increase and the temperature of phase transition to the super ionic phase is approaching the room temperature, which is optimal for the work of above-mentioned opto-electronic devices. Influence of added TiO2 nano-particles, and applied γ -irradiation on the morphology and nano-dimensions in electrolytes, was studied by small-angle X-ray scattering (SAXS) with simultaneous measurement of differential scanning calorimetry (DSC). Measurements were performed at SAXS beam-line of synchrotron ELETTRA in Trieste. Higher conductivity is achieved by the decrease of crystallinity as a result of the decrease of the size of spherulites. The growth of spherulites is suppressed with the crosslinking and addition of nano-particles of TiO2, which was confirmed by different methods. Addition of nano-particles increased conductivity more than can be ascribed to crystallinity possibly because of interactions of anion with nano-particles. The significant role that the nano-dimensions of the electrolyte material play in Zn2+ -ion mobility, oxygen reduction in TiO2 nano-grains and cross-linking are discussed. Assumption is that change of properties for different treatments is caused by change in size of nano-grains, which are different combinations of crystalline part of PEO and/or crystallites of ZnCl2 as well as nano-particles of TiO2. SAXS information on average grain sizes change during the phase transition gave insight to the microscopic mechanism of ionic transport in nanocomposite polymer electrolyte.

Polymer electrolyte; SAXS/DSC

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