Chain configuration at critical miscibility of polymer solution

Abstract

Abstract The application of a thermodynamic theory of flexible-chain polymer solutions indicated, in a previous work, that even at the theta temperature a polymer coil was significantly expanded over the unperturbed dimension. This was interpreted to mean that the chain segments at the periphery of the coil were more extended than the average. At the critical miscibility point, which is below the theta temperature and which is defined by concentration and temperature for a given molecular weight of polymer, this excess expansion of the coil disappears. This conclusion was reached through a calculation of the coil equilibrium, that is, the “microther-modynamic approach.” In this work a “macrothermodynamic approach” was used, because it enables us to evaluate the coil expansion from the conditions of critical miscibility. The results are in agreement with the previous ones that at the critical miscibility point, there is no excess expansion of the coil. The chain segments at the periphery of the coil are no...