Temperature dependence of the χ‐parameter between polystyrene and polyisoprene

The temperature dependence of the interaction parameter χ between polystyrene and polyisoprene was investigated. Cloud point, PVT and small angle X‐ray scattering measurements were performed. From various cloud point curves, χ was determined via the Flory‐Huggins theory. Using the PVT‐‐data, χ could be calculated using an equation‐of‐state approach due to Patterson, and the solubility parameter approach. For both methods, the well‐known Berthelot relationship proved to work well, i. e. no adaption of parameters to the experiments was required. Moreover, χ was determined from X‐ray scattering data, using the random phase approximation. Finally these parameters are compared, and in addition parameters determined from X‐ray scattering on diblock copolymers are included. It turns out that the temperature dependence of the χ‐parameters does not depend too much on the method of determination, its absolute value, however, does.