Stress-strain relation of entangled polymer networks

The non-linear stress-strain relation for cross-linked polymer networks is studied using molecular dynamics simulations. Previously we demonstrated th e importance of trapped entanglements in determining the elastic and relaxa tional properties of networks. Here, we present new results for the stress versus strain for both dry and swollen networks. Models which limit the flu ctuations of the network strands like the tube model are shown to describe the stress for both elongation and compression. For swollen networks, the t otal modulus is found to decrease like (V-0/V)(2/3) and goes to the phantom model result only for short strand networks. (C) 2000 Elsevier Science B.V . All rights reserved.