Dynamics of heterogeneous polymer networks

This paper discusses the effect of heterogeneities in cross-link density on network dynamics. The dynamic effects of such networks are studied in two limits, i.e., at short times and at long times. It is shown that heterogeneities in cross-link density alter the chain dynamics strongly. This has several effects on the segmental motion, ruled by an additional time scale that is set mainly by fluctuations in the cross-link density. It is shown that the chains localize more strongly in the long-time limit as given in homogeneous rubbers. The localization of chains is essential for the dynamic response of networks. The collective dynamics of the whole network is investigated by the use of a F\"orster transfer model, which encounters the heterogeneities on larger scales. This method has not been applied to networks previously and leads to predictions on creep dynamics and long-time moduli.