Negative C₂ values of inhomogeneous polymer networks measured in elongation

Abstract

It was found that negative slopes of the Mooney‐Rivlin plot (negative C2 values) can be expected for polymer networks prepared by means of a crosslinking polymerization of respective monomers in the presence of large concentrations of a diluent, or for such systems having macroscopic porosity. Some examples are given for swollen poly (2‐hydroxyethyl methacrylate) networks prepared in the presence of high concentrations of water (porous systems), and/or ethylene glycol (nonporous systems), and also for a network of partially hydrolyzed polyacrylonitrile prepared in a similar way. Negative C2 parameters are probably connected with inhomogenous deformations of supramolecular domains in the stressed cross section of the systems studied.