ELECTROCHEMICAL PROPERTIES AND HYDRATION OF CATION-EXCHANGE MEMBRANES BASED ON SULFONATE-CONTAINING POLYETHYLENEPHTHALAMIDES

Electrochemical characteristics and hydration behavior of cation-exchange membranes based on sulfonate-containing aromatic polyamides were studied. These polyamides were synthesized via condensation of sodium 4,4'-diaminophenylamino-2-sulfonate and m-phenylenediamine, taken in different ratios, with isophthaloyl chloride. Electroconductivity, transport numbers, and water regain of the cation-exchange membranes were studied as a function of the molar content of the chain fragment containing a sulfo-group (a = = 30 - 100 mol %). On increasing the molar fraction of this fragment from 30 to 50 - 60 mol %, a sharp growth in electroconductivity from 10(-5) to 10(-3) OMEGA-1 cm-1 was observed. When the molar content was < 70 mol %, electroconductivity was shown to depend on the nature of the cation and tended to decrease in the following order: Na+ > K+ > Cs+ > Li+. The polymer composition of a polyamide-based cation-exchange membrane, which corresponds to high transport numbers (0.95 - 0.99) and high transport selectivity of various cations, was determined.