MECHANICAL-BEHAVIOR OF SWOLLEN NETWORKS

A network immersed in solvent is a semi-open thermodynamic system. The immersed network may absorb solvent if stretched and give out solvent if compressed. Measurements on networks of relatively low degrees of cross-linking immersed in solvents show that a large amount of solvent enters the network upon stretching even at relatively small extension ratios. Such large dimensional changes resulting from the movement of solvent into the network affects the elastic properties of the networks significantly. Elastic parameters, such as modulus of elasticity, shear modulus, bulk modulus and Poisson's ratio, depend strongly on the interaction of the polymer with the solvent. Values of elastic parameters are calculated in the present study for networks as a function of cross-link density, interaction parameter and degree of ionization.