Abstract
Uniaxial elongation or compression has often been used to characterize the finite deformation behavior of polymer gels. We demonstrate that biaxial stretching experiments under varying the strains independently in the two directions provide stress-strain data in a wide range of strain revealing the essential features of nonlinear elasticity of polymer gels. We introduce the analysis of the biaxial stretching data for the three types of gel: Highly swollen hydrogels with a water content of 98%, Tetra-PEG gels with nearly uniform network structure, and slide-ring gels whose cross-links are movable along network strands.
