The structure of colloidal alloy crystals revealed by ultra-small-angle neutron scattering

We investigated the structure of colloidal crystals in binary colloidal dispersion by the ultra-small-angle neutron scattering (USANS) technique. The mixed dispersion of deutrated polystyrene latex (d-PS) and hydrogenated polystyrene latex (h-PS) dispersions (the size ratio α=0.54) was prepared for the USANS experiment to apply the contrast matching technique. The scattering from the each component could be detected separately. We also extracted the partial scattering intensity IdPS-hPS(q) at three mixing ratios. The USANS scattering profiles at the contrast matching point for each component were changed clearly with the change of the mixing ratio of d-PS and h-PS lattices. The IdPS-hPS(q) profile obtained for the d-PS number fraction xdPS03=0.39 indicated the correlation between d-PS and h-PS particles. These USANS observation suggested strongly the formation of the liquid-like colloidal alloy structure in the binary colloidal dispersion.