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research papers
Small-angle X-ray scattering from semidilute solutions of poly(N-isopropylacrylamide) in 1-propanol-water mixtures has been measured in a poor-solvent regime. The binary and ternary cluster integrals of polymer segments were determined from the concentration dependence of the correlation length at several temperatures just below the lower critical-solution temperature. The contributions of the segment-segment interactions to the entropy Sint and enthalpy Hint have been calculated from the temperature dependence of interaction parameters (binary and ternary cluster integrals) and it has been found that both values are positive. The dependence of Sint on the concentration of propanol does not show a simple linear relationship.