Effects of disorder and chain stiffening on the elasticity of flexible polymer networks

摘要

We examine how the distribution of contour lengths and the high-stretchstiffening of individual chain segments affect the macroscopic shear modulus offlexible polymer gels, using a 2D numerical model, in which polymer segmentsform a triangular network and disorder is introduced by varying their contourlengths. We show that in the relevant parameter range: (i) the non-affinecontribution to the shear modulus is negligible, i.e. the Born approximation issatisfactory; (ii) the shear modulus is dominated by the contributionoriginating from equilibrium chain tensions. Moreover, mechanical equilibrationat the nodes induces specific correlations between the end-to-end distances andcontour lengths of chain segments, which must be properly accounted for toconstruct reasonable estimates of chain pressure and shear modulus.