Temperature, composition and molecular-weight dependence of the binary interaction parameter of polystyrene/poly(vinyl methyl ether) blends

The binary interaction parameter χeff has been obtained for deuterated polystyrene/poly(vinyl methyl ether) blends as a function of temperature, composition and molecular weight from small-angle neutron scattering experiments. The consistency of the correlation length ξ, the zero-wavenumber scattering intensity S(0) and the χeff parameter with the mean-field prediction has been demonstrated by the q dependence of the static structure factor S(q) and the 1/T dependence of ξ−2, S(0)−1 and χeff. The effective interaction parameter χeff can be related to the Flory-Huggins interaction parameter χeff can be related to the Flory-Huggins interaction parameter χF. The free-energy function as well as the spinodal curve and cloud-point curve have been constructed.