Rheology and scaling relations in the LAOS regime during the sol-gel transition

The sol-gel transition in various polymeric systems and the resulting network formation have been extensively studied in the past by means of small amplitude oscillatory shear (SAOS) and the Winter–Chambon (W–C) model. This study investigates the validity of the W–C criteria in the large amplitude oscillatory shear (LAOS) regime for systems in the vicinity of the critical gel point. Mainly, it is focused on the manifestation of the universal self-similarity property in the rheological data for various polymeric systems of different chemical structures, chemically or physically cross-linked, end-linked or randomly cross-linked along the backbone, and either bulk or solution cross-linked. The results reveal that the critical relaxation properties of the network remain preserved across both SAOS and LAOS regimes, despite the large range of the applied strain amplitudes. However, the gel strength shows a strain-dependence in the LAOS regime, indicating changes in the network resistance to deformation. Remarkably, the degree of cross-linking at the gel point and the values of the critical exponent determined in the nonlinear regime align closely with those obtained in the linear regime, demonstrating the robustness of the W–C criteria even at large deformations.