PROTON-CONDUCTING MEMBRANES BASED ON MODIFIED POLYVINYLIDENE CHLORIDE

Polyvinylidene chloride was obtained by radical polymerization of vinylidene chloride and its sulfonation was carried out. When concentrated sulfuric acid is used as a sulfonating agent, the sulfonation process proceeds in the direction of dehydrochlorination of the vinylidene chloride units, and as a result, an insoluble black reaction product is formed. Therefore, sodium sulfite was chosen as the sulphurizing agent. The optimal conditions for the reaction of polyvinylidene chloride with sodium sulfite were found, while the maximum sulfur content in the modified polyvinylidene chloride, according to elemental analysis, was 3.2%. In the IR spectrum of the modified polyvinyl-idene chloride, the stretching vibrations of the C-Cl bond in the region of 660 cm-1 are preserved, but absorption bands appear characteristic of the sulfogroup (1250 and 1130 cm-1) and dehydro-chlorinated units of polyvinylidene chloride (1630-1670 cm-1). This means that the reaction of pol-yvinylidene chloride with sodium sulfite is accompanied by dehydrochlorination of vinylidene chlo-ride units. The temperature of the start of decomposition of polyvinylidene chloride containing sulfonic acid groups, according to thermogravimetric analysis, is 250 degrees C, which is 30 degrees C higher than for the original polymer. The theoretical total ion-exchange capacity of the modified polyvi-nylidene chloride, calculated from the sulfur content, is consistent with the experimental values and is 1.0 meq/g and is close to the similar value for the Nafion membrane. Based on polyvinylidene chloride containing sulfonic acid groups and polyvinyl alcohol, a membrane was obtained and the dependence of proton conductivity on temperature was studied. As the temperature rises from 30 degrees C to 80 degrees C, a monotonic increase in proton conductivity is observed from 6.7 center dot 10-3 S/cm to 1.8 center dot 10-2 S/cm with an activation energy of 17 +/- 1 KJ/mol. The mechanical properties of the mem-brane have been studied.