Mechanical Behaviors of Mechanochemical Materials : Part 1, Junction of Networks and Equilibrium Swelling of a Mechanochemical Material

Abstract

There is little quantitative knowledge about mechanical behaviors of mechanochemical materials which directly convert the chemical energy into a mechanical one like the muscle. In this paper a formulation of entropy change involved in deformation is presented. The formula developed is different in the coefficient of the logarithmic term from the one currently accepted, in which an uncross linked polymer is assumed to be in an initial state in regard to the deformation of network and the effect of the association of dissolved chains is considered. The latter contains the pressure exerted by undeformed network while the former does not contain it. In the present paper, it is considered that a probability (Ω₂) associated with the uncrosslinked chains is independent of entropy change involved in the deformation after the formation of cross-linkages, because the size and shape of the volume element must change under deformation. An equation of equilibrium swelling was derived from the corrected formula of the elastic entropy change and the osmotic pressure due to effective gegen-ions. The physical meaning of the equation is simple and clear. Theoretical results based on the equation agree well with experimental ones for a particle-like or a film-like material.