(WO9400502-A1)      Membrane comprises a linear copolymer having pendant unsatd. gps. where copolymer comprises (a) ether of formula CF2=CF-CF2-Q-O-CF=CF2 (1) in which Q is -O-C2J4-; and J is F three times and -CF3 once; and (b) a component of formula C2F3-O-C2F4-SO2F (2) in which the -SO2F gp. is converted to an ionic gp. Copolymer pref. comprises 0.3-25 mole% (a) and 75-99.7 mole% (b). The -SO2F gp. of (b) is pref. converted to an ionically charged substit. pref. by hydrolysis with an aq. alkaline soln. Membrane can be cured to crosslink the copolymer, pref. thermally.    USE/ADVANTAGE -   Melt processable polymer, opt. crosslinked to improve the strength, elasticity and tear resistance of the finished prod. can be fabricated into a membrane used in electrolytic fuel and chlor-alkali cells.    (JP7508779-W)      Membrane comprises a linear copolymer having pendant unsatd. gps. where copolymer comprises (a) ether of formula CF2=CF-CF2-Q-O-CF=CF2 (1) in which Q is -O-C2J4-; and J is F three times and -CF3 once; and (b) a component of formula C2F3-O-C2F4-SO2F (2) in which the -SO2F gp. is converted to an ionic gp. Copolymer pref. comprises 0.3-25 mole% (a) and 75-99.7 mole% (b). The -SO2F gp. of (b) is pref. converted to an ionically charged substit. pref. by hydrolysis with an aq. alkaline soln. Membrane can be cured to crosslink the copolymer, pref. thermally.    USE/ADVANTAGE -   Melt processible polymer, opt. crosslinked to improve the strength, elasticity and tear resistance of the finished prod. can be fabricated into a membrane used in electrolytic fuel and chlor-alkali cells. In an example, mixt. of 22g 2-fluorosulphonyl tetrafluoroethyl trifluorovinyl ether and 2.3g 3,6-dioxa-5-trifluoromethyl perfluoronona-1,8-diene was emulsified with a mixt. of 1.03g Na dihydrogenphosphate, 1.25g Na mono-hydrogenphosphate, 0.32g ammonium persulphate and 1.66g surfactant in 300ml deionised water. Mixt. was stirred at 55 deg.C. and tetrafluoroethylene (TFE) was charged at 100psi. Reaction mixt. was kept at 100psi unit 19g was absorbed over 81 min. After releasing the pressure, 50ml dil. HCl was added to coagulate the polymer which was recovered in a yield of m35g and had a sulphonyl fluoride equiv. wt. of 636 g/eq. Obtd. copolymer was pressed at 0.5 ton and 210 deg.C into a disk, cured under N2 at 270 deg.C for 20 hr, vacuum-dried at 100 deg.C for 24 hrs. and immersed in 25 wt.% NaOH with stirring at 60 deg.C for 3 days. Disk was washed with dionised water, kept in boiled deionised water for 2 hr and vacuum dried at 80 deg.C for 24 hr. Change of weight and vol. before and after hydration were +65.5% and +105, cf. +73.4% and +164% for a disk absorbing water in an uncured state.