Preliminary investigations into organic-inorganic composite formation: The system DDAB-H₂O-MMA-CaSO₄

Preliminary investigations were performed to test the possibility of synthesizing organic-inorganic composite materials utilizing the self-organizing tendency of surfactant-based systems. The strategy was to precipitate inorganic calcium sulfate particles in the aqueous channels of the bicontinuous cubic phase of a system made up of the following three components: (1) a hydrophobic monomer solution of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA); (2) an aqueous solution of calcium and sulfate ions; and (3) a surfactant, didodecyldimethylammonium bromide (DDAB). In addition to the precipitation process, the monomer was polymerized by ultraviolet light in order to solidify the structure of the cubic phase. Polarized light microscopy was used to study the unpolymerized mixtures. Fourier transform infrared spectroscopy studies were made to characterize the chemistry of the polymerized samples, and scanning electron microscopy was used to study their morphology. The solid polymerized samples were observed to have thread-like or lamellar structures at the micron scale with pockets of calcium sulfate precipitates in the poly(methyl methacrylate) (PMMA) matrix. At certain concentrations, the precipitates were found to be aligned perpendicularly to the polymer threads.