Aligning halloysite nanotubes in elastomer toward flexible film with enhanced dielectric constant

Naturally occurring halloysite nanotubes (HNTs) are considered electrically insulating counterparts of carbon nanotubes, and they are always randomly distributed in the reported polymer composites. With the recent optimization in advanced processing techniques for the production of muti-functional polymer composites, efficiently aligning micro-/nano-fillers in polymer matrix have been available. Here, we fabricate such aligned HNTs-silicon elastomer (PDMS) composites enabled by alternating current (AC) electric field driven alignment and report that at 7 wt% HNTs loading, the dielectric constant of aligned HNTs/PDMS composite film is almost 150 % (8.46 vs 5.71) higher than that of unaligned one at measurement frequency of 1 kHz. It is also observed that such high loading of nanoparticles brings negligible increase in dielectric loss and does not compromise much of the flexibility. This work provides a renewed understanding of the potential of aligning fillers in polymer matrix, allowing the proper utilization of the high polarization and extremely low dielectric loss predicted for HNTs in the fabrication of polymer composite dielectrics.