Self-assembled topological transition via intra- and inter-chain coupled binding in physical hydrogel towards mechanical toughening

Mechanical robustness is one of the challenges for soft hydrogels, which are difficult to repair once fractured, mainly because of their chemical bonds and large binding energies required to heal the fractured surfaces within a reasonable time scale. In this study, an extended Maxwell model is proposed to describe intra-chain ionic bonds and inter-chain hydrogen bonds, coupled in physical hydrogels undergoing self-assembly and mechanical toughening, during both of which the intra-chain and inter-chain bonds are working as sub-entanglement and physical crosslink, respectively. According to the rubber elastic theory, a topology model is formulated to identify the working principle of intra-chain and inter-chain coupled binding in the physical hydrogels. Furthermore, a constitutive stress-strain relationship is developed to understand their self-assembling topology signatures and topological transitions. Finally, effectiveness of the proposed model is verified using molecular dynamic simulations and experimental results of physical hydrogels reported in literature.