Intercalation-enhanced electric polarization and chain formation of nano-layered particles

Abstract

Microscopy observations show that suspensions of synthetic and natural\nnano-layered smectite clay particles submitted to a strong external electric\nfield undergo a fast and extended structuring. This structuring results from\nthe interaction between induced electric dipoles, and is only possible for\nparticles with suitable polarization properties. Smectite clay colloids are\nobserved to be particularly suitable, in contrast to similar suspensions of a\nnon-swelling clay. Synchrotron X-ray scattering experiments provide the\norientation distributions for the particles. These distributions are understood\nin terms of competing (i) homogenizing entropy and (ii) interaction between the\nparticles and the local electric field; they show that clay particles polarize\nalong their silica sheet. Furthermore, a change in the platelet separation\ninside nano-layered particles occurs under application of the electric field,\nindicating that intercalated ions and water molecules play a role in their\nelectric polarization. The resulting induced dipole is structurally attached to\nthe particle, and this causes particles to reorient and interact, resulting in\nthe observed macroscopic structuring. The macroscopic properties of these\nelectro-rheological smectite suspensions may be tuned by controlling the nature\nand quantity of the intercalated species, at the nanoscale.\n