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Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

Published online by Cambridge University Press:  01 February 2011

Kazuki Nakanishi
Affiliation:
Department of Material Chemistry, Graduate School of Engineering, Kyoto University Yoshida, Sakyo-ku, Kyoto 606–8501, JAPAN
Souichi Kumon
Affiliation:
Department of Material Chemistry, Graduate School of Engineering, Kyoto University Yoshida, Sakyo-ku, Kyoto 606–8501, JAPAN
Kazuyuki Hirao
Affiliation:
Department of Material Chemistry, Graduate School of Engineering, Kyoto University Yoshida, Sakyo-ku, Kyoto 606–8501, JAPAN
Hiroshi Jinnai
Affiliation:
Department of Polymer Science and Engineering, Kyoto Institute of Technology Matsugasaki, Sakyo-ku, Kyoto 606–8585, JAPAN
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Abstract

Macroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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References

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