Effect of octadecylamine-functionalised SWCNTs on the elastic constants and electro-optic response of a liquid crystal

Abstract

For efficient and high-performance liquid crystal (LC) devices, the physical properties of the LC materials can be suitably altered by incorporating nanomaterials like carbon nanotubes (CNTs), graphene and quantum dots. In the present work, the effect of incorporation of octadecylamine-functionalised single-walled carbon nanotubes (ODA-SWCNT) in a LC exhibiting nematic and smectic phases on its physical properties is investigated. The electro-optic threshold voltage in the nematic phase of ODA-SWCNT nanocomposite of LC is enhanced as compared to that of pure LC. The dielectric anisotropy as a function of reduced temperature decreases with an increase in the concentration of ODA-SWCNT. The ratio of bend to splay elastic constants of ODA-SWCNT nanocomposite of LC is enhanced considerably as compared to that of pure LC at low temperature. The electro-optic response rise time decreased and decay time increased at higher concentrations of ODA-SWCNT. The temperature range of smectic phase is increased with an increase in the concentration of ODA-SWCNT. At the lower concentration of ODA-SWCNTs (0.05 wt%), the anchoring of the nanotubes at the LC–electrode interface is favoured. At higher concentration of the ODA-SWCNTs, in addition to the anchoring at the interface, the nanotubes that are dispersed in the LC medium increases the orientational ordering.

Keywords:

• liquid crystals
• functionalised SWCNT
• dielectric anisotropy
• elastic constant
• electro-optic response time

Acknowledgements

The author VM gratefully acknowledges DST, India, for the support provided under SERC Fast track scheme (SR/FTP/PS-10/2009). Authors from BITS, Pilani, also gratefully acknowledge UGC, India, for DRS-SAP. JK is thankful to UGC, India, for BSR fellowship.