Segment-segment interactions of poly( N -isopropylacrylamide) in aqueous methanol solutions by using small-angle scattering

Abstract

Small-angle neutron and X-ray scattering from semidilute solutions of poly(N-isopropylacrylamide) in D2O, methanol and methanol–water mixtures has been measured in the poor solvent regime. The binary and the 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. Then, contributions of segment–segment interactions to the entropy and the enthalpy have been calculated from the temperature dependence of interaction parameters and it has been found that both values are positive in the D2O and the methanol–water systems at a small content of methanol, while both values are negative in the other system.