AbstractA quasi‐thermodynamic model for expansion of polymer configuration in solution is investigated. The model is based on Gaussian distribution of segments and mean field theory of polymer solution. An in‐homogeneous contribution to the free energy of solution is proposed. It arises from the nonhomogeneous distribution of polymer segements. This effects makes the expansion factor α to be larger than those without the effect considered. Some numerical consequence for the case Polydimethylsiloxane+cyclohexane solution is calculated. Our theory predicts a larger value a than the case without inhomogeneous effect being considered. The difference becomes less significant at higher molecular we