Viscoelastic dynamic properties of heterogeneous polymer networks with domain structure

Abstract

A dynamic model of a heterogencous polymer network system is proposed. A polymer network is presented as an ensemble of cross-linked regions (domains) of different sizes. the domains have similarly regular internal structures. To a first approximation, these domains are treated independently of each other. Relaxation modulus, storage modulus, and loss modulus of the heterogeneous polymer network are calculated. For the purpose of averaging over all network domains the exponential number distribution of chain segments in domains is used. This type of distribution has been previously proposed by one of the authors in the frame of the aggregation model. It is shown that a structure heterogeneity introduced into a network model according to the above domain approach leads, at long times, to the stretched exponential type of time dependence of relaxation modulus instead of the power-law dependence predicted by the theories dealing with regular networks. The network heterogeneity also leads to a more rapid decrease in the storage modulus in the region of low frequencies. as compared with regular polymer networks. It is shown that the loss modulus in the region of its maximum is very slightly sensitive to the long-range network heterogeneity considered.