Synthesis of porous polymeric membranes by polymerization of micro-emulsions

Abstract

In this study the polymerization of monomer-containing micro-emulsions to yield porous polymeric membranes is demonstrated. A micro-emulsion system composed of methyl methacrylate and acrylic acid as monomers, ethyleneglycol dimethacrylate as crosslinking agent, sodium dodecylsulfate as surfactant and water was studied. An identical surfactant-free system, formed using the same monomers, crosslinking agent and water but without surfactant, was also studied and the micro-emulsions formed at certain compositions were polymerized. Our earlier work with these systems had indicated the porous morphology of the polymer to be dependent on the microstructure of the precursor micro-emulsion. In the present study micro-emulsion compositions which showed inferential evidence of a bicontinuous structure were polymerized to form membranes by using photo-initiated polymerization with ultra-violet radiation. The membranes formed had a thickness of 10–12 μm. The swelling characteristics in water of the polymeric material constituting the membranes was evaluated as a function of pH. The tensile properties of the membranes were also evaluated. The permeability of the membranes was examined using aqueous solutions of acrylic acid. The results indicate the permeability of the membranes to be dependent on the composition of the precursor micro-emulsion due to the relationship between the polymer morphology and micro-emulsion structure. This study conclusively shows the feasibility of synthesizing porous polymeric membranes by utilizing the structure of micro-emulsions.