Temperature Dependence of the Interaction Parameter of Polystyrene and Poly(methyl methacrylate)

The Flory-Huggins interaction parameter, χ, has been determined for polystyrene, PS, and poly(methyl methacrylate), PMMA, by measuring the small-angle neutron scattering, SANS, from P(S-6-MMA), symmetric, diblock copolymers above the microphase separation temperature. The SANS profile can be well described by the correlation hole scattering from which χ is easily obtained. Measurements as a function of temperature yield χ = (0.028 ± 0.002) + (3.9 ± 0.06)/Γ where Τ is the absolute temperature. These results show that the entropie contribution of χ is much greater than the enthalpic contribution and that the temperature dependence of χ is weak. © 1990, American Chemical Society. All rights reserved.