(DE19535086-A1)      A polymeric solid electrolyte, has a backbone (partly) functionalised by ionic gps., the backbone is a copoly(m-phenylene). It contains 20 mole-% m-phenylene units and is of formula (I); where R1-8 = H, aryl, oxyaryl, thioaryl, sulphonylaryl, carbonylaryl, oxyaryloxyarl, OH or an ionogenic gp.    USE -   The electrolyte is used as polymer electrolyte membrane in fuel or electrolytic cells (all claimed).    ADVANTAGE -   In contrast to rigid rod polyphenylenes, substitution with side chains is not essential for processability (solubility). The mfg. process is quicker and hence cheaper than usual. The polymers also have improved thermal and chemical stability.    (EP852071-A2)      A polymeric solid electrolyte, has a backbone (partly) functionalised by ionic gps., the backbone is a copoly(m-phenylene). It contains 20 mole-% m-phenylene units and is of formula (I); where R1-8 = H, aryl, oxyaryl, thioaryl, sulphonylaryl, carbonylaryl, oxyaryloxyarl, OH or an ionogenic gp.    USE -   The electrolyte is used as polymer electrolyte membrane in fuel or electrolytic cells (all claimed).    ADVANTAGE -   In contrast to rigid rod polyphenylenes, substitution with side chains is not essential for processability (solubility). The mfg. process is quicker and hence cheaper than usual. The polymers also have improved thermal and chemical stability.    (JP11515040-W)      A polymeric solid electrolyte, has a backbone (partly) functionalised by ionic gps., the backbone is a copoly(m-phenylene). It contains 20 mole-% m-phenylene units and is of formula (I); where R1-8 = H, aryl, oxyaryl, thioaryl, sulphonylaryl, carbonylaryl, oxyaryloxyarl, OH or an ionogenic gp.    USE -   The electrolyte is used as polymer electrolyte membrane in fuel or electrolytic cells (all claimed).    ADVANTAGE -   In contrast to rigid rod polyphenylenes, substitution with side chains is not essential for processability (solubility). The mfg. process is quicker and hence cheaper than usual. The polymers also have improved thermal and chemical stability.