An analytic study of the NMR properties for deformed polymer networks blended 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 isotropic excluded volume interactions. For a uniaxial deformation lambda the splitting is proportional to (lambda(2) - lambda(-1)) and inversely proportional to the molecular weight of the network chains. The dominant contribution depends linearly on the network fraction and is directly related to the ratio of the Edwards screening length to the length 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 effects can be strongly enhanced. A variety of specific predictions are made as the phase separation point is approached which reflect the statistical mechanics of the process.