Electro-optical memory of a nematic liquid crystal doped by multi-walled carbon nanotubes

TL;DR

This paper investigates the electro-optical memory effect in nematic liquid crystals doped with multi-walled carbon nanotubes, revealing a mechanism involving nanotube network formation that enables bistability and potential new device applications.

Contribution

It introduces a novel understanding of the irreversible memory effect caused by nanotube network formation and dispersion in nematic liquid crystals.

Findings

Memory effect linked to MWCNT network formation

Irreversible homeotropic-to-planar reorientation observed

Absence of memory in polymer-fixed composites

Abstract

A pronounced irreversible electro-optical response (memory effect) has been recently observed for nematic liquid crystal (LC) EBBA doped by multi-walled carbon nanotubes (MWCNTs) near the percolation threshold of the MWCNTs (0.02-0.05 wt. %). It is caused by irreversible homeotropic-to-planar reorientation of LC in an electric field. This feature is explained by electro-hydrodynamically stimulated dispergation of MWCNTs in LC and by the formation of a percolation MWCNT network which acts as a spatially distributed surface stabilizing the planar state of the LC. This mechanism is confirmed by the absence of memory in the EBBA/MWCNT composites, whose original structure is fixed by a polymer. The observed effect suggests new operation modes for the memory type and bistable LC devices, as well as a method for \textit{in situ} dispergation of carbon nanotubes in LC cells.