A IPN membrane of hydrophilic polyurethane(PU) and hydrophobic polystyrene(PS) was prepared by polymerizing the isocyanate terminated PU prepolymer with chain extender and styrene monomer with divinylbenzene simultaneously.
The effects of composition, crosslink density($\bar{M}_c$), and the molecular weight of the polyethylene glycol (PEG) on the properties of IPN membranes formed were studied.
The swelling ratio of the water-ethanol mixture, thermal and mechanical properties, and separation characteristics of the IPN membranes were measured. The swelling ratio, defined as the weight ratio of the swollen and dry membrane, showed a broad maximum at around 70 wt. % ethanol content. Both water and ethanol permeated the PU-PS IPN membrane, but the separation factor increased with increasing ethanol concentration when pervaporation of ethanol water mixture was carried out.
Water permeabilities and solute rejection characteristics were also investigated in ultrafiltration experiment. Water permeability increased as higher mol. wt. PEG was used and at higher $\bar{M}_c$, but decreased as the PS contene increased. Compared to the commercial polymer membrane, Cuprophane, IPN membranes prepared with PEG 1000 showed higher water permeabilities. The IPN membranes rejected the solutes of mol. wt. of $10^2 - 10^3$.
