Neutron diffraction from shear ordered colloidal dispersions

Recently, it has been pointed out that the structure of shear ordered colloidal dispersions can adequately be accounted for by the intensity distribution I(l) along Bragg rods [Phys. Rev. Lett. 75, 763 (1995)]. Information concerning packing of the shear induced layers and on their stacking order is contained in I(l). In this paper I(l) is determined by measuring the small angle neutron scattering distribution as a function of the sample orientation. For the investigated charge stabilized system with particle diameter sigma=143 nm and a distance of nearest neighbors in the layers a=237 nm, a structure close to random close-packed hexagonal layers is found. As compared with close-packed systems the distance between the layers c is elongated so that c approximate to a. Further, it is shown that the application of shear leads to a more uniform distribution of I(l) along the rods, which demonstrates that the loss of correlation between the hexagonal layers under sheared conditions can also be determined by small angle neutron scattering. (C) 1996 American Institute of Physics.