Magnetic birefringence of montmorillonite dispersion

Abstract

Compared with unadulterated polymers, filler/polymer composites can exhibit superior properties. Modulating the orientation of montmorillonite (MMT) filler may maximize this filler’s properties in shape-anisotropic applications. We measured the magnetic birefringence of MMT dispersions in water with custom magnetic birefringence equipment and estimated the inherent birefringence and anisotropic magnetic susceptibility of MMT. We classified polydisperse MMT to prepare MMT dispersions with a narrow size distribution. From the relationship between the retardation obtained by magnetic birefringence measurements and the reciprocal of the square of the magnetic field, we estimated the inherent birefringence of MMT to be −0.060. Considering the size distribution, and by setting the anisotropic magnetic susceptibility to −1.5 × 10−5, we reproduced the magnetic flux density dependence of the magnetic birefringence of MMT with a particle size of ≤300 nm.