Finite extensibility and deviation from Gaussian elasticity of dimethylacrylamide-based gels with different charge density: Insight into pH/solvent-dependent swelling and surfactant interactions

The prediction of the effect of swelling on the stress-strain behavior from small to large deformation levels remains a challenging issue for true characterization of rubber elasticity. Highly-swollen P(DMAAm-co-NaA) hydrogels showed deviation from Gaussian behavior with a scaling parameter 0.31. Due to the presence of the charges on the hydrogel matrix and the osmotic pressure of counter-ions, the polymer chains are highly extended and thus far from the Gaussian coil state assumed in the classical theory.306