(A) Study on the pervaporation separation of water-ethanol mixture through PAA-P(BMA-co-MMA) IPN composite membranes

Abstract

For the separation of liquid mixtures, IPN structure could be used to enhance the mechanical strength and the selectivity of membrane by restricting the swelling of the transporting polymer component networks. In this study, for water/ethanol separation, composite membranes having polyacrylic acid - poly (buthyl methacrylate acid-co- methyl methacrylate acid) interpenetrating polymer network [PAA-P(BMA-co-MMA) IPN] skin layer supported on cross-linked porous poly(BMA-co-MMA) were prepared by polymerizing in the presence of solvent and followed by immersion precipitation. Morphology changes and the factors involved in the pore formation of the cross-linked porous sublayers were also investigated. Final morphology of the sublayer revealed three types of morphology depending on the amount of added solvent and degree of cross-linking: (1) non-porous structure with higher degree of cross-linking; (2) porous cellular structure with lower degree of cross-linking; (3) finger-like structure with lower degree of cross-linking and higher solvent content. We could obtain cross-linked highly porous interconnected poly(BMA-co-MMA) sulayer by polymerizing with 70% NMP and $\bar{M}_c$ = 40,000. We believe the excess solvent causes the formation of macrovoids and porous cellular structure is obtained due to the delayed demixing of the system containing solvent lower than equilibrium swelling ratio. Composite membrane with porous x-P(BMA-co-MMA) sublayer has a hydrophilic/hydrophobic IPN skin layer with about 10㎛ thickness. Using AFM images it was found that the skin layer has no defect. For the pervaporation of water-ethanol mixtures, new composite membranes having poly acrylic acid - poly (butyl methacrylate - co - methyl methacrylate) interpenetrating polymer network [PAA-P(BMA-co-MMA) IPN] skin layer supported on porous and crosslinked poly(BMA-co-MMA) were prepared. The composite membranes were prepared by polymerizing surface coated AA monomer mixtures on the x-P(BMA-co-...