| Abstract: | Monte-Carlo simulations of the elastic behaviour of PDMS networks, using a realistic (R-I-S) network-chain model, are able to reproduce experimentally observed deviations from Gaussian network behaviour in uniaxial extension. The finite extensibility of the network chains is shown to cause non-affine deformation of the mean-square network-chain end-to-end distance, even at moderate sample deformations (λ≈1.5). An increase in the proportion of fully-extended chains with increasing macroscopic strain gives rise to a steady decrease in the rate of network free-energy change, causing a reduction in the network modulus at moderate macroscopic strains. There is no need to invoke a transition from affine to phantom chain behaviour as deformation increases. |
