Membranes and processes for preparing membranes having weakly acidic or weakly basic groups comprising the steps of: (i) applying a curable composition to a support; (ii) curing the composition for less than 30 seconds to form a membrane; and (iii) optionally removing the membrane from the support; wherein the curable composition comprises a crosslinking agent having at least two acrylic groups. The membranes are particularly useful for producing electricity by reverse electrodialysis.