TEMPERATURE-DEPENDENCE OF THE CHI-PARAMETER BETWEEN POLYSTYRENE AND POLYISOPRENE

The temperature dependence of the interaction parameter chi between po lystyrene and polyisoprene was investigated. Cloud point, PVT and smal l angle X-ray scattering measurements were performed. From various clo ud point curves, chi was determined via the Flory-Huggins theory. Usin g the PVT-data, chi could be calculated using an equation-of-state app roach due to Patterson, and the solubility parameter approach. For bot h methods, the well-known Berthelot relationship proved to work well, i.e. no adaption of parameters to the experiments was required. Moreov er, chi was determined from X-ray scattering data, using the random ph ase approximation. Finally these parameters are compared, and in addit ion parameters determined from X-ray scattering on diblock copolymers are included. It turns out that the temperature dependence of the chi- parameters does not depend too much on the method of determination, it s absolute value, however, does.