Langmuir, Vol.15, No.2, 345-352, 1999
Charge-stabilized liquidlike ordered binary colloidal suspensions. 2. Partial structure factors determined by small-angle neutron scattering
In this paper we present small-angle neutron scattering (SANS) studies on liquidlike ordered binary colloidal suspensions. Using perfluorinated (sigma(PFA) = 162 nm) and polystyrene (sigma(PS) = 79 nm) particles, we prepared samples made of the same colloids as in the preceding paper. All system parameters of the mixtures were as before. Via neutron contrast variation we directly obtained all three partial intensities IPFA-PFA(Q), IPFA-PS(Q), and IPS-PS(Q) and partial structure factors SPFA-PFA(Q), SPFA-PS(Q), and SPS-PS(Q) The experimental results are compared with theoretical predictions for binary colloidal mixtures, based on the pure repulsive part of the DLVO potential. Within the hypernetted chain (HNC) closure an accurate agreement is achieved. The particle correlation in the mixtures is clarified by means of the partial distribution functions g(ij)(r) and the one-component effective pair potentials U-PFA-PFA(eff)(r) and U-PS-PS(eff)(r). From this we deduce for the examined suspensions a partial clustering or local demixing by attractive interaction contributions of depletion origin.