HIgher Order Structure of Polymer Gels induced by Phase Separation

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Gelation process of poly(vinyl alcohol) (PVA) solutions in mixtures of dimethyl sulfoxide (DMSO) and water and glycelol and water have been studied using wide angle neutron scattering, small angle neutron scattering, light scatttering, ultra small angle neutron scattering and conforcul laser scanning microscope techniques. It was found that cross-linking points of the PVA gels are crystallites and the average distance between the crystallites is about 200 *. The gels formed above about -20 。C are opaque, suggesting that microphase separation occurs before the gelation. This expectation was directly confirmed by time resolved light scattering measurements. The higher order structure induced by the microphase separation was observed by conforcul laser scanning microscope. It was suggested in this research that how to control the phase separation process is a key to control the higher order structure which is closely related to microscopic properties of the gels.