Preparation of Photonic Crystals by Immobilization of Colloidal Crystals of Polymer-Modified Particles Formed in Organic Media

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(1)Preparation of monodisperse, polymer-modified silica and colloidal crystallization in organic solventsThe preparation of poly(maleic anhydride-co-styrene)(P(MA-ST))-and poly(methyl methacrylate)(PMMA)-grafted silica was successfully achieved by the reaction of monodisperse colloidal silica, of 136 nm size, suspended in ethanol with corresponding polymer silane having trimethoxysilyl group. The particles of P(MA-ST)/SiO_2 and PMMA/SiO_2 made colloidal crystallization in polar organic solvents, such as acetonitrile or acetone. The dependences of the critical volume fraction for the crystallization on solvent polarity, amounts of grafted polymer or its molecular weight were disclosed.(2)Immobilization of colloidal crystals in polymer gelsPhoto-irradiated radical copolymerization of methyl methacrylate and 1,2-dimethacryloyloxyethane in the suspension forming colloidal crystals successfully gave organogels preserving the crystal structure. The addition of N-alkyl-L-amino acid derivatives to the suspension also afforded physical gels contained the crystals. The immobilization in the gels was recognized to be a promising procedure for making photonic crystals, because of no contraction during geling.(3)Solidification of gel-immobilized colloidal crystalsThe exchange of acetonitrile in the gel for vinylidene oxolane and following radical polymerization resulted in the formation of durable polymer containing particle array of the colloidal crystal structure. The particle array in the polymer block was observed by SEM and TEM spectroscopy. The solvent exchange with methyl methacrylate and the polymerization gave a transparent poly(methyl methacrylate) film containing silica particle array.(4)Photo-electric effects of colloidal crystal gelsIt was observed that applying alternating currency to the colloidal crystal gel induced oscillation of crystal lattice, which was suggested to be applicable to a photonic crystals.