Porous polymers

A highly porous crosslinked, functionalised polymer, crosslinked from 1 to 20% and having interconnected cavities or chambers of micron dimensions whose total pore volume is greater than 85% (5.6 cc/g) in its solvent swollen state and having a capacity for spontaneous water absorption from its dry state of at least 3 g liquid per gram of polymer and having a capacity for saline absorption (10% NaCl) such that the ratio of saline to water absorption is greater than 0.1, said polymer comprising structural units ##STR14## in which A represents a crosslinked carbon chain, Y is an optional spacer group and Z is an ionic or polar functional group, selected from lower alkyl cationic quaternary nitrogen groups of 10 carbon atoms or less, alkyl amine oxide groups of 8 carbon atoms or less, alkyloxy groups, a metal or ammonium or substituted ammonium salt of a sulphuric, carboxylic, phosphoric or sulphonic acid group or a mixture of such groups, except that where Z is a sulphonic acid Y does not represent ##STR15##