DIFFUSION OF ORGANIC-COMPOUNDS THROUGH CHEMICALLY ASYMMETRIC MEMBRANES MADE OF SEMIINTERPENETRATING POLYMER NETWORKS

The design of high performance pervaporation membranes for the selecti ve removal of ehtanol from ethyl t-butyl ether (ETBE) and toluene from heptane was performed by using semi-interpenetrating polymer network (s-IPN) materials. With cellulose acetate butyrate as the linear polym er and the polyethylene glycol dimethacrylate (PEGDMA) as the monomer to be photopolymerized to form the s-IPN materials, membranes with goo d mechanical and separation properties were obtained for both applicat ions. The nature of the gas (nitrogen or air) above the polymer soluti on during the photopolymerization step changes the s-IPN structure in the membrane thickness, making it possible to prepare both homogeneous and chemically asymmetric membranes from the same dope formulation. T he solvent diffusion characteristics depend on several parameters; the most interesting one is the nature of the membrane face in contact wi th the liquid medium in the pervaporation through a chemically asymmet ric membrane. When the appropriate face of asymmetric membranes is use d in contact with the liquid medium, the ratio of the two solvent diff usion coefficients becomes much higher, and an improvement in the perv aporation selectivity from that of the homogeneous membranes can be ex cepted. (C) 1998 Elsevier Science B.V. All rights reserved.