Abstract
In this paper, we investigate a commercial nematic liquid crystal (LC) mixture namely E7 dispersed with small concentrations of multi-walled carbon nanotubes (MWCNTs). The dielectric and electro-optical characterizations have been carried out in the homogeneously and vertically aligned LC cells. The electro-optical response of LC molecules has been enhanced by 60% after the addition of MWCNTs, which is attributed to the reduced rotational viscosity in the composites. MWCNTs act like barricades for ionic impurities by reducing them up to ∼34.3% within the dispersion limit of 0.05 wt%. The nematic–isotropic phase transition temperature (TNI) of the E7 LC has also been shifted towards the higher temperature, resulting in a more ordered nematic phase. The enhanced birefringence and orientational order parameter in the LC-MWCNTs are attributed to π-π electron stacking between the LC molecules and the MWCNTs. The outlined merits of the LC-MWCNTs composites evince their suitability for ultrafast nematic-based electro-optical devices.
Highlights
Liquid crystal (LC) materials are ubiquitous in everyday life
The homogeneous dispersion of multi-walled carbon nanotubes (MWCNTs) in the E7 LC is evident from polarized optical micrographs (POMs)
The dispersion of MWCNTs in the E7 LC into different concentrations leads to the change in color of POMs, which is associated to the change in refractive index and/or birefringence (∆n) as reported previously [42,43,44]
Summary
Liquid crystal (LC) materials are ubiquitous in everyday life. It has a wide range of commercial applications such as reliable displays for the several electronic devices [1], tunable filters and lenses for ophthalmic applications [2,3], smart windows [4], various components of medical equipment [5], sensors for chemical, biological and satellite applications [6,7,8], and many more. The concept of Guest–Host mode has been proposed to enhance the physical properties of the pristine LCs [9]. With this consideration, the coupling of nanotechnology with that of the soft condensed mesogens (i.e., LC–nanomaterial composites) have drawn a significant interest from researchers for obtaining superior display and nano-display applications [10]
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