Rouse's dynamics of networks with pendant chains

A model to describe the dynamics of networks with linear pendant chains has been formulated based on the properties of ensembles of micronetworks, usi ng the Rouse model.(1) This development indicates that the terminal relaxat ion time of pendant chains with relatively large molecular weight scales wi th the square of the molecular weight of those chains. On the other hand, w hen the molecular weight of pendant and elastically active chains are compa rable, a nearly exponential growth of the terminal relaxation time with the molecular weight is predicted. The main predictions of the model are compa red with experimental results of model poly(dimethyl siloxane) (PDMS) netwo rks, with controlled amounts of linear pendant chains of known molecular we ight. The terminal relaxation time of these networks was estimated from the values of the loss modulus G "(omega) measured experimentally. An exponent ial dependence on the molecular weight of pendant chains was derived for th e terminal relaxation time. This behavior is in good agreement with the pre dictions of our model for micronetworks, provided that the friction coeffic ient scales linearly with the number of entanglements. (C) 1999 John Wiley & Sons, Inc.