ABSTRACT
The neutron scattering technique is now currently used in order to study polymer networks (“dense” rubbers, or swollen rubbers i.e. gels). The first series of experiments were essentially devoted to the probe, at molecular scales, of the mechanism of network deformation: it was an attempt to check the more directly possible the validity of the hypotheses underlying the rubber elasticity theories [1] (for a review of the main theories see [2-5]). For instance, the swelling of a gel was originally described only on the basis of an extension of the elementary strands (or meshes) of the network in the three directions of space [2]. The neutron scattering results modified this vision. Roughly speaking, they led to compare the swelling - at least in the case of a gel prepared in the presence of solvent - to a kind of unfolding of the network from a “crumpled” or “interspersed” state at high concentrations of polymer [6,7]. Along this scheme, an eventual extension of the meshes is a second order perturbation resulting from a sort of feed-back of the expansion.
