Background

Ionic liquid crystals, mesogenic materials composed of charged molecules, are noted for their ability to conduct charge through the movement of ions and/or electrons. They are lightweight and can be processed as liquids above their melting points. These properties make these structures of interest for application in optoelectronic devices. Their organic semi-conductive properties make them suitable for use in OLEDs and organic solar cells, as well as electrolytes for batteries, where they are more stable and safer than liquid electrolytes.

However, useful conductivity is typically only observed in the liquid crystal mesophase, with conductivity decreasing significantly below the liquid crystal-crystal phase transition temperature as molecules rearrange into a different configuration in response to temperature changes. As a result of this, such liquid crystals may only be operable in electronic devices at higher temperatures and over narrow temperature ranges.

Technology Overview

The present invention is a novel class of ionic compounds which is capable of forming a columnar liquid crystal mesophase and which retains conductivity through the liquid crystal-to-crystal phase transition. In addition, the compounds retain their conductivity into the isotropic phase. This allows the materials to be used over a wider temperature range than conventional discotic liquid crystals. They can be processed as neat liquids or solutions before setting as semi-conductive solids at room temperature.

Stage of development

A series of mesogenic cyclopropenium compounds have been synthesised, based on a triphenyl cyclopropenium core. Phase behaviour and conductive properties have been measured. The synthesised materials showed either hexagonal columnar or rectangular columnar liquid crystal phases. Where a hexagonal phase is present for the material, the conductivity is retained through the isotropic, liquid crystal and solid phases.

Benefits

This work shows the capabilities of these liquid crystals to act as charge transport materials, and their ability to retain the phase structure and charge transfer properties into the solid phase. The materials can be used in applications where the dielectric properties of the liquid crystal are desired within the temperature range of the solid. Therefore the benefits include:

Easier processing (as a liquid)
Improved device safety (solid vs liquid electrolyte)
Lightweight organic material

Applications

Use in optoelectronic devices, displays, solar cells, batteries, OLEDs
Lightweight organic electrolytes

Opportunity

Durham University is seeking expressions of interest from suitably positioned industry partners to take forward the commercial development of this novel series of compounds.

Novel Conductive Discotic Liquid Crystal

Patents

IP Status

Seeking