ELECTRIC ALIGNMENT OF LIQUID CRYSTALLINE BINARY COLLOIDS OF MICROMETER-SIZED NIOBATE AND CLAY NANOSHEETS

抄録

Among colloidal systems of inorganic nanosheets prepared by exfoliation of inorganic layered crystals, binary colloids of two different nanosheet species are important for their multicomponent and multiphase coexistence, which is applicable to new materials. Nevertheless, electric response of binary nanosheet colloids has scarcely been paid attention although that of single-component nanosheet colloids has recently been investigated. We report herein the electric alignment of aqueous binary nanosheet colloids of niobate K₄Nb₆O₁₇ and synthetic fluorohectorite, both of which have large lateral sizes of a few micrometers. In the binary colloids, the niobate nanosheets respond to an applied AC electric voltage to be aligned in parallel to the electric field. Although the clay nanosheets also respond to an AC electric field in their single-component colloids, their alignment is basically suppressed in the binary colloids. However, combined optical microscope observations of bright-field, polarized, and fluorescence detections indicate that large clay platelets are partly involved in the aligning motion of the niobate nanosheets. As a result, some of the clay platelets are aligned in parallel to the electric field. Colloidal liquid crystallinity of the niobate nanosheets contribute to the alignment of the clay particles by incorporating the latter particles to the liquid crystalline domains of the former ones.