Electric-field-induced out-of-plane alignment of clay in poly(dimethylsiloxane) with enhanced anisotropic thermal conductivity and mechanical properties

An Alternating current (AC) electrical field was applied to induce the movement of the clay nanoparticles in polydimethylsiloxane (PDMS) to fabricate flexible membranes embedded with thickness-direction aligned nanoparticles. The influence of the electric field strength and frequency on the movement of the particles in the PDMS monomer was investigated using an optical microscope. The morphology of the aligned clay/PDMS membranes frozen with thermal curing was analyzed with scanning electron microscopy (SEM) and confocal Raman spectroscopy. Benefiting from the anisotropic structure of aligned particle chains, the aligned clay/PDMS membranes show enhanced mechanical properties, thermal conductivity, and the light transmittance in the thickness direction compared to nonaligned membranes. This enhancement effect decreases as the particle concentration exceeds 5 wt %. The reason is that at higher clay concentrations, alignment of the particle is frustrated and particle chains become tilted and irregular owing to an increment in the viscosity of the system.