Bicontinuous-nanostructured polymeric materials from microemulsion polymerization

Abstract

Transparent bicontinuous nanostructured polymeric materials have been synthesized via the polymerization of bicontinuous microemulsions of appropriate formulations. The use of polymerizable zwitterionic betaine surfactant of (acryloyloxy)undecyldimethylammonio acetate (AUDMAA) and cationic surfactant (acryloyloxy)undecyltrimethylammonium bromide (AUTMAB) is the key factor to the success of the stable polymerization. The nanostructures (pores) of polymeric materials were characterized by SEM, thermoporometry, and membrane-filtration of poly(ethylene glycol) having different molecular weights. The pore size or the width of the polymerized bicontinuous microemulsions (transparent solid polymers) increased substantially from about 20 to 100 nm with the increase of the water content (20-60 wt %) or NaCl concentration (0-2 wt %) in precursor microemulsions. In contrast, the incorporation of 12 wt % HEMA in the precursor microemulsion reduced the pore size drastically to about 2 nm. This total polymerization (except water) approach enables one to synthesize various bicontinuous nanostructures (2-150 nm) of transparent polymeric materials by simply adjusting the concentrations of water, HEMA, polymerizable surfactant, and electrolyte in precursor bicontinuous microemulsions.