The effect of solvent and proton donor type on the conductivity and physico-chemical properties of poly(vinylidene fluoride)-based proton-conducting gel electrolytes

In the present work proton-conducting gels based on commercially available poly(vinylidene fluoride) (PVdF) system are studied. The polymer, H3PO4 and phosphoric acid organic esters (used as proton donors) are dissolved in di methylformamide (DMF) or dimethyl acetate (DMA) at ambient temperatures and than cast on the Aat glass substrate. Highly conducting (similar to 10(-3) S cm(-1) at 20 degreesC) colorless polymeric membranes are obtained in a r elatively narrow PVdF and proton donor concentration ranges. The highest co nductivities have been obtained when phosphoric acid esters are used as pro ton donors. Conductivities measured fur systems containing DMF are slightly higher than for DMA-based derivatives. The gel electrolytes studied are th ermally stable up 100 degreesC as shown by the DSC experiments. The interac tions between H3PO4 and solvents used are studied by means of FT-IR spectro scopy which shows the possibility of the protonation of solvent molecules b y H3PO4. Therefore, the possibility of proton transportation via the Grotth us-type mechanism cannot be excluded. (C) 2000 Elsevier Science B.V. All ri ghts reserved.