(US6090895-A)   NOVELTY - A method of making a crosslinked polymer comprises crosslinking a polymer having either (a) pendent acid halide groups using a crosslinker which bonds to one or more acid halide groups, to form one or more groups of pKa less than 5; or (b) pendent amide groups using a crosslinker which bonds to one or more amide groups, to form one or more groups of pKa less than 5.    USE - For making crosslinked polymers suitable for use in ion-conductive membranes (ICM), e.g. membranes containing a polymeric electrolyte used as solid electrolytes in electrochemical cells.    ADVANTAGE - The method can produce a crosslinked ICM having crosslinks which are stable to oxidation and hydrolysis without loss of the polymer's acidic functionality. The membranes, including commercially available membranes, may be crosslinked after casting. The crosslinked films are methanol insoluble and show reduced swelling in water (e.g. a 40% weight gain when soaked in water overnight). They have a high proton conductivity (e.g. 0.02-0.06 S/cm) at room temperature, which is close to the conductivity of an uncrosslinked membrane, and a higher mechanical strength than prior art membranes.    (EP1077758-A1)   NOVELTY - A method of making a crosslinked polymer comprises crosslinking a polymer having either (a) pendent acid halide groups using a crosslinker which bonds to one or more acid halide groups, to form one or more groups of pKa less than 5; or (b) pendent amide groups using a crosslinker which bonds to one or more amide groups, to form one or more groups of pKa less than 5.    USE - For making crosslinked polymers suitable for use in ion-conductive membranes (ICM), e.g. membranes containing a polymeric electrolyte used as solid electrolytes in electrochemical cells.    ADVANTAGE - The method can produce a crosslinked ICM having crosslinks which are stable to oxidation and hydrolysis without loss of the polymer's acidic functionality. The membranes, including commercially available membranes, may be crosslinked after casting. The crosslinked films are methanol insoluble and show reduced swelling in water (e.g. a 40% weight gain when soaked in water overnight). They have a high proton conductivity (e.g. 0.02-0.06 S/cm) at room temperature, which is close to the conductivity of an uncrosslinked membrane, and a higher mechanical strength than prior art membranes.