Mechanical Response of Hybrid Cross-Linked Networks to Uniaxial Deformation: A Molecular Dynamics Model

Networks combining physical and covalent chemical cross-links can exhibit a large amount of dissipated inelastic energy along with high stretchability during deformation. We present our analysis of the influence of the extent of covalent cross-linking on the inelasticity of hydrogels. Four model networks, which are similar in structure but strongly differ in elasticity, have been studied. The aim was the identification of a key structural factor responsible for observing a hysteresis or an elastic deformation. In the employed molecular dynamics study this factor is derived from the underlying structure of each particular hydrogel network. Several structural characteristics have been investigated like the extent of damage to the network, chains sliding, and the specific properties of load-bearing chains. By means of such a key factor, one can predict the deformation behavior (hysteresis or elasticity) of some material, provided a precise description of its structure exists and it resembles any of the four types of a network. The results can be applied in the design of bio-inspired materials with tailored properties.