Swelling and deformation of gels: Is it possible to make these processes more homogenous

The authors have studied by Small Angle Neutron Scattering a series of neutral gels swollen in good solvent, prepared by different methods. In all cases, both the swelling and the elongation seem to be achieved, on molecular scales, in a strongly inhomogenous way. This behavior can be understood as the manifest of a preexisting large scale structure (namely some topological inhomogeneities of the network) which is more and more coupled to the fluctuations of polymer concentration as the gel is strained (swollen or stretched). On the other hand, fixing electrical charges along the chains makes the swelling or the uniaxial deformation much more homogeneous (in terms of polymer concentration): the observed behaviors become then much more compatible with the usual picture of an evenly deformed meshwork. However, when salt is added to the sample, its seems to recover the inhomogenity of stretching observed in practice in the case of neutral gels.