  The mechanical properties of a polymeric network containing both crosslinks
and sliplinks (entanglements) are studied using a multi-chain Brownian dynamics
simulation. We coarse-grain at the level of chain segments connecting
consecutive nodes (cross- or sliplinks), with particular attention to the
Gaussian statistics of the network. Affine displacement of nodes is not
imposed: their displacement as well as sliding of monomers through sliplinks is
governed by force balances. The simulation results of stress in uniaxial
extension and the full stress tensor in simple shear including the (non-zero)
second normal stress difference are presented for monodisperse chains with up
to 18 entanglements between two crosslinks. The cases of two different force
laws of the subchains (Gaussian chains and chains with finite extensibility)
for two different numbers of monomers in a subchain (no = 50 and no = 100) are
examined. It is shown that the additivity assumption of slip- and crosslink
contribution holds for sufficiently long chains with two or more entanglements,
and that it can be used to construct the strain response of a network of
infinitely long chains. An important consequence is that the contribution of
sliplinks to the small-strain shear modulus is about &#8532; of the
contribution of a crosslink.
