A porous polyimide film having a three-layer structure that comprises two surface layers (a) and (b) and a macrovoid layer sandwiched between the surfaces layers (a) and (b). The macrovoid layer has a partition wall bonding to the surface layers (a) and (b...

A hydrophilic cross-linked polymer obtainable by copolymerisation of hydrophobic and hydrophilic monomers that give a cross-linked hydrophilic polymer on polymerisation; a monomer including a strongly ionic group; and water is useful as the membrane in an ...