Neutron Scattering Investigation of the Loss of Affineness in Deswollen Gels

Abstract

Polymer networks swollen with a solvent of the linear chains of same nature are usually called gels. In these materials the rubber elasticity manifests itself not only in the classical way, when they are uniaxially stretched, but also tridimensionally: as first recognized by Frenkel [1], the swelling equilibrium can be considered as the result of a competition between the “osmotic” tendency of polymer dilution and an “entropic” elastic retraction of the network. Because polymer networks are commonly synthesized in presence of a solvent, i.e. in a gel state, an important part of the research activity in the rubber elasticity field has been devoted to the study of the swelling and deswelling mechanism. In this regard, it is of particular interest to know how the macroscopic volume change of the sample affects the chain conformation. This kind of information can be gained using the neutron scattering technique applied to selectively labelled networks.