solvent is n n dimethyl acetamide additional representative solvents include formic acid acetic acid and sulfuric acid the polymer solutions may be prepared for example by dissolving sufficient polybenzimidazole in the solvent to yield a final solution containing from about 4 to 30 percent by weight of polymer based on the total weight of the solution and preferably from about 10 to 20 percent by weight the quantity of polybenzimidazole dissolved in the solvent should be such that the resulting solution has a viscosity of about 50 to 4 000 poise at 30 u00b0 c and preferably about 200 to 3000 poise one suitable means for dissolving the polymer in the solvent is by mixing the materials at a temperature above the normal boiling point of the solvent for example about 25 u00b0 to 120 u00b0 c above such boiling point and at a pressure of 2 to 15 atmospheres for a period of 1 to 5 hours the resulting solutions are preferably filtered to remove any undissolved polymer a minor amount of lithium chloride optionally may be provided in the solution in accordance with the teachings of u s pat no 3 502 606 the lithium chloride prevents the polybenzimidazole polymer from phasing out of the solution upon standing for extended periods of time to the above polybenzimidazole solution is added a divinylsulfone which has the following general formula str4 wherein r 1 r 4 are the same or different and are h or c 1 c 3 alkyl according to the instant invention it is believed that crosslinking occurs via a modified michael type.