Topographically induced homeotropic alignment of liquid crystals on self-assembled opal crystals

Kumar, Pankaj; Oh, Su Yeon; Baliyan, Vijay Kumar; Kundu, Sudarshan; Lee, Seung Hee; Kang, Shin‐Woong

doi:10.1364/oe.26.008385

Cited by 25 publications

(16 citation statements)

References 47 publications

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“…This provided mechanical nano-groove planar alignment of the nematic liquid crystal with a negligible pretilt angle. 21 Inorganic thin solid films, for example silicon dioxide and associated solid dielectrics, commonly provide a polar anchoring energy of the order of 10 À5 J m À2 22 similar to conventional polyimide 23 and polyvinyl alcohol alignment layers. 24 Magnesium fluoride thin films have previously been used to align twisted nematic cells in the literature, giving a comparable electro-optical performance to polyimide alignment layers.…”

Section: Device Details and Preparationmentioning

confidence: 99%

Electrically controlled topological micro cargo transportation

et al. 2020

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Section: Device Details and Preparationmentioning

confidence: 99%

Electrically controlled topological micro cargo transportation

et al. 2020

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“…Consequently, a surface topology change leads to a HA state by inducing a sufficient degree of elastic distortion to surpass the effects of surface anchoring. 15 The evidence about the surface morphology is going to be dealt with in surface analysis.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Fullerene-Based Nanosurfactant for the Automatic Homeotropic Alignment of Liquid Crystals

Park

Kim

Yoon

et al. 2023

ACS Appl. Nano Mater.

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Chemically functionalized organic–inorganic hybrid nanoparticles have significant benefits for automatic liquid crystal (LC) alignment but are still limited to well-balanced self-assembly without wasting materials and deleterious aggregation for LC display. In this paper, we propose a promising homeotropic alignment (HA) guide nanosurfactant (C60D) consisting of different distinct molecular segments in LC affinity. By doping C60D into a nematic LC medium, the HA nanolayer is automatically constructed on the surface and guides the good alignment of LC molecules. Notably, this system exhibits exceptional material efficiency (0.01 wt %). Furthermore, it is demonstrated that an electro-optical switching modulator using C60D is reliably working. The precisely developed HA-guide C60D nanosurfactant will offer a way for LCD application as well as a useful guideline for designing nanomaterials.

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“…This is supported by our observation that chloroform-treated 140 nmthick brushes, which exhibit an rms roughness of 2.1 ± 0.2 nm, induces planar LC alignment, while chloroform-treated 12 nmthick brushes, which exhibit an rms roughness of 2.3 ± 0.2 nm, induce homeotropic alignment. Prior studies 45 have reported that surface roughness can influence the orientations of LCs, but those studies employed surfaces with rms roughness values that were much larger than 2 nm.…”

Section: Resultsmentioning

confidence: 99%

Using Liquid Crystals to Probe the Organization of Helical Polypeptide Brushes Induced by Solvent Pretreatment

et al. 2021

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Grafted polymer brushes form the basis of a versatile class of surfaces with properties that can be tailored via choice of the chemical functional groups or architecture of the grafted polymers. Here, we explore how treatment by solvents can program the organization of homopolymer brushes comprising helical poly(γ-benzyl-Lglutamate) (PBLG) and how the orientational behavior of liquid crystals (LCs) contacted with the brushes can provide fresh insights into brush organization. We treated PBLG brushes with either good (chloroform) or poor (acetone) solvents to form collapsed or teepee-like grafted polymer organizations, respectively. When supported on PBLG brushes with thicknesses [determined by atomic force microscopy (AFM)] of 50 nm, we found that collapsed and teepee-like brushes induced planar (parallel to surface) and homeotropic (perpendicular to surface) orientations of nematic LCs, respectively. By preparing solvent-pretreated brushes with a range of thicknesses (12−140 nm), and by combining insights based on AFM, Fourier-transform infrared spectroscopy and LCs, we found that a continuous change in tilt of the LC is accompanied by a continuous change in tilt of the PBLG chains, as influenced by the teepee-like organization. The role of PBLG chain orientation in dictating the LC orientation was confirmed by additional experiments in which PBLG brushes were thermally denatured. Finally, when using mixed solvents (mixtures of chloroform and acetone) to manipulate the PBLG brush organization, we observed LCs to exhibit patterned orientations on the micrometer scale, consistent with patterned orientations of the PBLG chains imprinted by droplets formed during the mixed solvent drying process. Overall, these results expand our understanding of the range of PBLG brush organizations that can be induced by solvent pretreatment and demonstrate the utility of LCs for imaging PBLG chain orientation within brushes.

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Topographically induced homeotropic alignment of liquid crystals on self-assembled opal crystals

Cited by 25 publications

References 47 publications

Electrically controlled topological micro cargo transportation

Electrically controlled topological micro cargo transportation

Fullerene-Based Nanosurfactant for the Automatic Homeotropic Alignment of Liquid Crystals

Using Liquid Crystals to Probe the Organization of Helical Polypeptide Brushes Induced by Solvent Pretreatment

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