SCATTERING IN POLYMER-SOLUTIONS - DETERMINATION OF OSMOTIC PROPERTIES IN THE CONCENTRATED REGIME

Concentrated solutions of poly(vinyl acetate)/toluene and poly(dimethyl siloxane)/octane were investigated in the polymer volume fraction range 0.08 less-than-or-equal-to phi less-than-or-equal-to 0.5 using small angle X-ray scattering. As the concentration increases the polymer-polymer correlation length deviates increasingly from the prediction of simple scaling theory. The osmotic compressibility governing the scattering intensity extrapolated to zero angle I(0) is satisfactorily described by a Flory-Huggins type equation containing an interaction parameter of the form chi + wphi. The coefficients of the interaction parameter are found to be PVAc/toluene: chi = 0.445 +/- 0.005, w = 0.15(3) +/- 0.01(1) PDMS/octane chi = 0.318 +/- 0.009, w = 0.15(7) +/- 0.02(0).