The synthesis of novel crosslinking agents N-acryloyl,N-methacryloyl methylenediamine (1) and N-acryloyl,N＇-methacryloyl ethylenediamine (2) with non-identical vinyl functionalities is described. When incorporated into crosslinked networks, the resultant polymers exhibit a higher degree of porosity than the more conventional systems where the vinyl functionalities are identical, as evidenced by protein mobility studies using electrophoresis and water permeability experiments. This may be attributed to the formation of a bimodal pore size distribution arising from a crosslinking mechanism which is dictated by the relative reactivities of the differentiated vinyl units within the novel monomers.