(7) Preparation of Organic/Inorganic Hybrid Particles by Utilizing Graft Layers as a Reactor

In the past decades, organic/inorganic hybrid particles have attracted much attention due to their unique and enhanced properties derived from synergistic effect of each component combined at a nanometerscale. In terms of a high concentration effect of hydroxide ion as a counter ion in the vicinity of protonated poly［2-（N,N-dimethylamino）ethyl methacrylate］（PDMAEMA） chain, metal oxides formed by a solgel process of metal alkoxides are expected to be deposited densely on PDMAEMA layers grafted on solid supports. Since our group has accumulated synthetic techniques of surface-initiated activators generated by electron transfer atom transfer radical polymerization（SI-AGET ATRP）for preparation of dispersed polymer materials in aqueous media, this article describes our strategy for preparation of organic/inorganic hybrid particles with a size range of several tens of nanometers to several micrometers. The submicrometerscale silica- and titania-hybrid particles were prepared by simply mixing PDMAEMA-grafted polymer latex particles with tetraethoxysilane and tetra-n-butyl titanate, respectively. The titania hollow particles with a photoactive anatase crystallographic phase can be easily obtained by heat treatment of titania-hybrid particles. The raspberry-like micrometer-scale silica hybrid particles were prepared by using heterocoagulates with PDMAEMA graft chains as a colloidal template. The cross-sectional SEM image revealed that PDAMEMA graft layers serve as a sol-gel reactor for metal alkoxides. The nanometer-scale hybrid particles were also obtained by using the oil-in-water（O/W）nanoemulsion droplets. O/W nanoemulsions were prepared by phase inversion temperature（PIT）emulsification using amphiphilic block polymers composed of PDMAEMA as a hydrophilic block. The void size and the shell thickness were found to be controlled independently by adjusting emulsification conditions.