Viscoelastic dynamic properties of meshlike polymer networks: Contributions of intra- and interchain relaxation processes

The theory of intra- and interchain relaxation processes for the local dynamic characteristics of meshlike polymer networks has recently been proposed by the authors (Macromolecules 1998, 31, 5756). The extension of this theory to macroscopic viscoelastic characteristics is presented. A regular cubic network consisting of "bead and spring" Rouse chains embedded in an effective viscous medium is considered. The viscoelastic response of the polymer network to an external stress producing a longitudinal velocity gradient in the effective viscous medium is studied. The comparisons of contributions from intra-and interchain relaxation processes to the dynamic modulus and viscosity of the Gaussian network are made. The asymptotic behavior of dynamic quantities considered is estimated for various limiting regions of frequency,The possibility of a simplified description of the viscoelastic properties of a polymer network in terms of a coarse-grained network model and a melt consisting of un-cross-linked chains is demonstrated. The problem of hydrodynamic interactions in polymer networks is also discussed.