Effects of irradiation on sulfonation of poly(vinyl fluoride)

Preparation and analyses of directly sulfonated poly(vinyl fluoride), PVF, membranes have been performed. Electron beam or proton irradiation was used for the production of reactive sites. Ion-exchange capacity, sulfonation efficiency and ion conductivity were analysed. Increases in the absorbed dose and in the linear energy transfer were found to have a promoting effect on the sulfonation rate and sulfonic acid content. In addition, compared with commercial ion-exchange materials, quite high ion-exchange capacities were achieved. The highest measured ionic conductivity of the materials was 20 mS cm(-1), which was achieved with proton-irradiated samples after long sulfonation times. On the basis of the results the proton irradiation is believed to cause the formation of channels with higher sulfonic acid content than those found in other domains of the matrix. The presence of these channels increases the ionic conductivity.