SynopsisReticulated polystyrene-divinylbenzene (PSt-DVB) copolymer membranes or thin sheets were prepared using two different methods. The first method employed a nonsolvating diluent which dissolves the monomer but precipitates the polymer. This resulted in skinned membranes with the skin being nonporous, being either crenelated or smooth. The second method used paraffin wax as the inert phase. The wax was precipitated by cooling, followed by polymerization of the styrene. The wax was then solvent extracted. This resulted in a reticulated structure both on the surface and in the interior of the membrane. The resulting products from the two methods were compared using scanning electron microscopy. The objective of this study was to prepare a skinless, macroporous, crosslinked polystyrene, as polymer I for the preparation of novel interpenetrating polymer network (IPN) materials.