Small-angle X-ray scattering and coexistence curve of semidilute polymer solutions

Abstract

Small-angle X-ray scattering from semidilute solutions of polystyrene in cyclohexane has been studied in a poor solvent regime. The values of binary and ternary cluster integrals of polymer segments were determined from the concentration dependences of the correlation length and the osmotic compressibility, as obtained from the absolute intensity at zero scattering angle, at various temperatures in the poor solvent regime. By using these interaction parameters the coexistence curve was calculated via a mean field theory. Excellent agreement was achieved between the calculated coexistence curve and the experimental phase separation points which we have measured.