On the optical anisotropy of bentonite gels

Optically anisotropic bentonite gels were synthesized and investigated. An investigation of the texture of the gels using polarization microscopy show ed that they cannot be reliably classed as nematic liquid crystals. It was found that the birefringence is due mostly to a deformation produced by ext ernal forces. It was speculated that the anisotropic phase results from the flow-induced orientation of anisometric structural units. Using scanning e lectron microscopy, it was found that bentonite particles in the gels have the shape of a 300-700 nm long and 200-300 nm wide "boat.".