MICROPOROUS POLYMERIC MATERIALS FROM MICROEMULSION POLYMERIZATION

A new microemulsion system consisting of water, methyl methacrylate (MMA), cross-linking agent ethylene glycol dimethacrylate (EGDMA), and a combination of 2-hydroxyethyl methacrylate (HEMA) and sodium 11-(N-ethylacrylamido)undecanoate (Na11-EAAU) was investigated. Both surfactant Na11-EAAU and cosurfactant HEMA are highly polymerizable monomers. Transparent polymeric solids could rapidly be formed by photoinitiated polymerization of some of these microemulsion compositions. It seems that a minimum of 21 wt % of Na11-EAAU is required for producing a single-phase (transparent) polymer network. Only about 4 wt % organic compounds could be extracted out from the polymers which were formed from the systems containing more than 15 wt % MMA. Scanning transmission electron micrographs of the polymeric materials reveal the existence of microporous structures. Open-cell porous structures of transparent polymeric solids could be obtained from those precursor microemulsions with water content higher than 20 wt %, while closed-cell structures from those with less than 20 wt % water. The microporous structures of these polymeric solids are related to the microstructures of the precursor microemulsions.