An isolated, flexible polymer chain in dilute solution assumes a random configuration. In reality such a polymer coil is not completely random, because an excluded volume effect requires a modification from randomness. In addition, the coil placed in a better solvent is more expanded than that in a poor solvent. In other words, the polymer chain segments in a better solvent are more extended, compared to those in a neutral solvent. In the present study we have discovered an indication that the chain segments lying on the periphery of the coil are more extended than those in the interior. This discovery has been made in the course of relating intrinsic viscosity to thermodynamic interaction between polymer and solvent. The resulting relationship provides a means of evaluating the thermodynamic interaction parameter from the measured value of intrinsic viscosity, if the molecular weight of the polymer, its intrinsic viscosity in a neutral solvent, and the degree of excess extension of chain segments are known. The last is the parameter discovered in this work. This observation is independent of particular thermodynamic theory, so long as the experimental data are used in a consistent manner. In this work Maron's theory was used, because it is applicable to infinite dilution as well as concentrated solutions.