Abstract: Process for the preparation of interpenetrating polymer network membrane, composed of hydrophilic-hydrophobic two phase structure with varying degree of segregation of the hydrophilic and hydrophobic component by a polymerization reaction comprising controlling the relative rate of polymerization of the component polymers, or controlling the reaction temperature and the reaction pressure during the interpenetrating polymer network forming reaction and particularly by a process which comprises, subjecting a monomeric reaction mixture to a simultaneous polymerization and crosslinking reaction or a sequential polymerization and crosslinking reaction, to produce at least a polymer network of a urethane resin of general formula (I) ##STR1## wherein R.sub.1 is ##STR2## wherein R.sub.3 stands for hydrogen or methyl group, n is integer of 1-3 and m is integer of 5-40,R.sub.2 is either ##STR3## wherein n is integer of 2-8, and styrene resin of general formula (II) ##STR4## wherein R.sub.4 is hydrogen or methyl group.