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. 2022 Dec 5;7(50):46466-46474.
doi: 10.1021/acsomega.2c05196. eCollection 2022 Dec 20.

Zinc Oleate Nanorod-Induced Vertical Alignment of Nematic Liquid Crystal

Shweta Mishra  1 , Manjuladevi V  1 , Raj Kumar Gupta  1
Affiliations

Zinc Oleate Nanorod-Induced Vertical Alignment of Nematic Liquid Crystal

Shweta Mishra et al. ACS Omega. .

Abstract

Nanocomposite zinc oxide nanorods capped with oleic acid (ZOR) with positive dielectric anisotropy liquid crystal (LC) 4'-octyl-4-biphenylcarbonitrile (8CB) filled in unaligned cells exhibit homeotropic alignment of host LC molecules. Further, systematic investigation of the textural, dielectric, and conductivity properties of nanocomposites filled in planar cells is performed with increasing concentration of nanorods. At a nanorod concentration ≤0.2 wt % in 8CB, the order parameter of nanocomposite samples is found to be increasing and ionic conductivity is found to be decreasing as compared to pure LC. Beyond 0.3 wt % concentration of nanorods in 8CB, vertical alignment (VA) of host LC is observed even in a planar aligned cell. The VA of LC molecules in ZOR nanocomposites is confirmed through attenuated total reflection-Fourier transform infrared absorption spectra studies.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(a) TGA curve during heating cycle under N2 flow, (b) powder XRD pattern, and (c) FE-SEM image of synthesized ZOR.
Figure 2
Figure 2
(a–d) Optical textures of pure and ZOR nanocomposites of 8CB (T = 35 °C) in planar cells (row 1), homeotropic cells (row 2), and unaligned cells observed under POM (numbers show CZOR in 8CB).
Figure 3
Figure 3
(left panel) FCM images and (right panel) analysis of FCM images of the (a) sample cell prepared by ZOR-coated ITO substrate and then filled with 8CB and (b) 0.05, (c) 0.3, (d) 2 wt % ZOR nanocomposites of 8CB (T = 35 °C) in planar cells. (e) FCM image of pure 8CB showing no fluorescence.
Figure 4
Figure 4
Birefringence (Δn) of pure and ZOR nanocomposites of 8CB (CZOR ≤ CZOR*) as a function of temperature.
Figure 5
Figure 5
Variation of (a,b) components of dielectric permittivity as a function of temperature, (c) threshold voltage ((CZOR ≤ CZOR*)), and (d) εdiff = εhigh(p) – εlow(p) for pure and ZOR nanocomposites of 8CB filled in planar cells as a function of temperature.
Figure 6
Figure 6
Variation of (a,b) components of bulk ac conductivity as a function of temperature; (c) bulk ac conductivity as a function of CZOR [numbers in the bracket denote T – TIN (°C)]; (d) thermal activation energy as a function of CZOR.
Figure 7
Figure 7
(a)ATR–FTIR absorption spectra and (b) variation of absorption intensity of IR bands as a function of CZOR of pure and ZOR nanocomposites of 8CB.
Figure 8
Figure 8
XRD pattern of pure and ZOR nanocomposites of 8CB.
Figure 9
Figure 9
Schematic representation of VA of 8CB due to incorporation of ZOR.
See this image and copyright information in PMC

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