The effect of chain correlations on the size of polymer coils in binary polymer blends

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Abstract
In order to study the size of the chains in binary polymer blends we determine the mean‐square end‐to‐end distance of the polymer coils of the A or B kind. Chains A and Binteract generating the one‐loop diagrams, which are summed up to all orders of concentration and interaction.Interactions that do not favor mixing are found to reduce the size of the macromolecules producing a deviation from the unperturbed dimensions of the order of 1/√N. The effect is stronger on chains of the smaller concentration whereas chains of large concentration and of large molecular weight, N→∞, tend to reach an ideal Gaussian behavior. Chains A are found to be more contracted when chains B are small acting as a bad solvent. As the system comes close to the phase separation limit, chains shrink obtaining a smaller size on the spinodal, where a second‐order phase transition is found. Our results are in accord with relevant SANS small angle neutron scattering and Monte Carlo experiments.