Multiaxial Stretching of Nearly Critical Gels with Extremely Low Modulus

Linear dynamic viscoelasticity of the gelation systems near the critical point has been investigated intensively, but the large deformation behavior of nearly critical gels, which are obtained slightly beyond the gelation point, remains to be characterized. In contrast to matured gels, nearly critical gels have very low modulus due to the extremely sparse network structures. In this study, we have characterized the large deformation of the nearly critical gels by using a custom-made biaxial tensile tester optimized for very soft gels. Biaxial tensile dada varying the strains in two directions independently provide a definite basis to discuss the whole aspects of the large deformation behavior. The biaxial tensile data have revealed that the nearly critical gels exhibit minimal cross-effect of strains which results only from volume conservation in contrast to the matured gels with finite cross-effect. The feature of the nearly critical gels is attributed to their extremely sparse network structures.