Nematic liquid crystal dispersed with two-dimensional functionalised graphene oxide (fGO): insights on improving the nematic ordering and reducing electro-optic response time

ABSTRACT

Doping a nematic liquid crystal (NLC) with nanoparticles (NPs) of varied dimensions and properties to form LC-NP nanocomposites with improved electro-optic and dielectric properties has recently been a much-explored field of work. But still, NLC nanocomposites based on two-dimensional (2D) NPs have not been studied vividly because of the high tendency of 2D NPs to aggregate together. In the present work, we have studied the effect of incorporating hexadecanethiol functionalised graphene oxide (fGO), a 2D NP, in a conventional NLC medium under varying doping concentrations. We found that at a lower doping concentration (⁓10⁻⁴ wt.%), the NLC nanocomposite showed a substantial increase in dielectric anisotropy (Δε) and birefringence (Δµ) values as compared to pure NLC sample. A significant decrease (⁓50%) in ionic conductivity as well as reduced electro-optic response time (⁓75%) was also observed in this NLC nanocomposite. As the fGO doping concentration was increased (⁓10⁻² wt.%), a reverse trend was observed for Δε, Δµ and response time values, which declined sharply with increasing doping concentration. Hence, the present work highlights two different working mechanisms at low- and high-doping concentrations of 2D NPs.

GRAPHICAL ABSTRACT

KEYWORDS:

• Nematic liquid crystal
• functionalised graphene oxide
• electro-optic response time
• dielectric anisotropy
• two-dimensional dopant
• nanocomposites

Acknowledgments

The author M.S. is thankful to Department of Physics, BITS Pilani for fellowship and author S.J.S is thankful to UGC India for the financial support under the scheme UGC CSIR fellowship. The author V.M. gratefully acknowledges DST, SERB, for the support provided under the project number (SPG/2021/002260). We are also thankful to the Department of Chemical Engineering, BITS Pilani, Pilani Campus for providing the DSC experimental facility.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data will be provided on request.

Additional information

Funding

This work was supported by the Science and Engineering Research Board [SPG/2021/002260].