Effects of entanglements and finite extensibility of polymer chains on the mechanical behavior of hydrogels

Abstract

Polymer networks usually have many entanglements as well as a finite extensibility due to the uncrossability and the full stretching of the network chains. In this paper, the nonaffine model proposed by Davidson and Goulbourne is adopted to characterize the influence of entanglements and finite extensibility of the polymer chains on the mechanical behavior of hydrogels. The Davidson–Goulbourne model only contains three material parameters and has a simpler mathematical form than the Edwards–Vilgis slip-link model, which is the only model that has been adopted to characterize the influence of entanglements on the swelling deformation of polymeric gels so far. Some benchmark problems such as free swelling, constrained swelling, uniaxial tension, equibiaxial tension in the immersed state and uniaxial compression in the isolated state are analyzed, respectively, based on the new constitutive equations. The results show that entanglements as well as chain extensibility have important influences on the mechanical response of hydrogels.