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R. Kishi, H. Ichijo, and O. Hirasa
[J. Intelligent Material Sys. and Stru., Vol.4, p.533, 1993]
Aqueous solution of poly(vinyl methyl ether) (PVME) shows phase transition around 38°C. PVME hydrogel cross-linked by γ-ray irradiation is also a thermally responsive hydrogel and undergoes volume change at the same temperature; it swells below and shrinks above 38°C. PVME hydrogel prepared near phase transition temperature has heterogeneous and macroporous structure. The volume change of the macroporous hydrogel takes place rapidly with changing temperature. An attempt has been made to develop thermally activated chemomechanical devices such as an artificial muscle model, an automatic separation system, an artificial finger model, and a photo-responsive device.