AN ANALYTIC STUDY OF THE NMR PROPERTIES FOR DEFORMED POLYMER NETWORKSBLENDED WITH FREE CHAINS

We show that when a network is deformed, the line splitting seen from NMR probe molecules located on the network or on free chains dissolved in the network can be accounted for by considering the effect of isot ropic excluded volume interactions. For a uniaxial deformation lambda the splitting is proportional to (lambda(2) - lambda(-1)) and inversel y proportional to the molecular weight of the network chains. The domi nant contribution depends linearly on the network fraction and is dire ctly related to the ratio of the Edwards screening length to the lengt h of the statistical segments. Smaller effects are present which also depend on the concentration, molecular weight, and chemical nature of the free chains as well as the molecular weight of the network chains. For chains which show a preference to microphase separate these effec ts can be strongly enhanced. A variety of specific predictions are mad e as the phase separation point is approached which reflect the statis tical mechanics of the process.