ACID AND BASE EFFECTS ON THE MORPHOLOGY OF COMPOSITES FORMED FROM MICROEMULSION POLYMERIZATION AND SOL-GEL PROCESSING

Phase behaviour studies were performed for microemulsions, containing organic monomers (methyl methacrylate and acrylic acid), inorganic mon omer (tetraethoxy silane (TEOS)), a cross linking agent (ethylene glyc ol dimethacrylate) and water, stabilized by a cationic surfactant, cet yltrimethylammonium bromide. Single phase transparent microemulsions w ere formed over a considerable portion of the composition domain. The effects of an acid, hydrochloric acid (HCl), and a base (NH4OH) on the gel times were studied and the catalytic action of acid and base on t he overall set-gel reaction was analysed. Organic/inorganic polymer co mposites were obtained from the hydrolysis and polycondensation reacti ons of TEOS (sol-gel process) and polymerization of organic monomers a nd inorganic monomer containing microemulsions. Scanning electron micr oscopy was used to examine the surface morphology of the composites. F or the acid and base studies a precursor microemulsion with pH 7.0) ex hibiting closed-cell microstructure upon polymerization was selected. The morphology was examined for polymerized microemulsions with the sa me base composition but with varying HCl to TEOS ratios or NH4OH to TE OS ratios. Pore continuity and morphology are strongly influenced by t he presence of acid or base. Both the HCl and NH4OH containing precurs or microemulsions led to open celled porous composites.