A novel thin film polarizer from photocurable non-aqueous lyotropic chromonic liquid crystal solutions

Bae, Yun-Ju; Yang, Hyejin; Shin, Seunghan; Jeong, Kwang‐Un; Lee, Myong‐Hoon

doi:10.1039/c0jm03882b

Cited by 42 publications

(44 citation statements)

References 14 publications

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“…Thus, developing an anchoring surface with high anchoring energy is essential to aligning lyotropic LCs via a surface‐anchoring approach. This can lead to various applications such as polarizing sheets, water‐based organic electronics, and biosensors . To investigate the aligning behavior of the lyotropic LCs on the BP surface, SSY was dissolved in water to a concentration of 35 wt% to prepare the nematic phase.…”

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confidence: 99%

Ultrastrong Anchoring on the Periodic Atomic Grooves of Black Phosphorus

Kim

Jeong

Kwon

et al. 2016

Adv Materials Inter

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the range of aligned molecules may be limited to those possessing strong π-π interactions with 2D materials. [19][20][21] In this regard, grooved surfaces can provide a powerful approach, because the anchoring energy and anchoring direction of their patterned surface can be artificially designed by controlling the direction, amplitude, and period of the patterned substrate according to Berreman's theory. [22][23][24] Despite the success achieved with aligning lyotropic chromonic liquid crystals (LC) by introducing patterned surfaces with high aspect ratio, [22] the anchoring energy of the grooved surfaces used in these attempts is still low for anchoring of various soft materials such as polymeric materials and dendrimers. This limitation is due to the restriction of the surface anchoring energy of the patterned surface to above 20 nm by the resolution of current lithographic techniques. [22][23][24] Here, we demonstrate for the first time that black phosphorus (BP) with atomic-scale grooves and a puckered honeycomb structure of adjacent phosphorus atoms enables alignment of a wide range of soft materials, including thermotropic LCs such as 4-cyano-4′-alkylbiphenyl (nCB) and 4-cyano-4′-alkyloxybiphenyl (nOCB), the lyotropic LC sunset yellow (SSY), and fluorinated dendrimers. Especially, SSY and dendrimer molecules are difficult to align through known surfaceanchoring techniques. We found that the planar direction of the aligned soft materials is fixed in a single direction, following the direction of the atomic grooves of BP. This result is attributed to the regular and atomic-scale grooves of BP with height of 2 Å and period of 4.33 Å. [26] These induce an ultrastrong azimuthal anchoring energy of soft materials, ≈0.235 N m −1 (for 5CB), which is two orders of magnitude higher than that of previously reported anchoring methods. Thus, our surface-anchoring technology represents a new approach for aligning a wide range of soft materials using well-designed atomic-scale grooves of BP. Such an approach can be used in various methods for realizing high-performance optoelectronic devices and biotechnological applications.The overall procedure for aligning various soft materials on the BP surface is illustrated in Figure 1. Briefly, BP flakes were exfoliated through a mechanical method using commercial 3M tape and then transferred onto SiO 2 /Si substrates for polarized optical microscopy (POM) observations and onto a Si nitride (SiN) grid for transmission electron microscopy (TEM) observations (Figure 1a). [27] The BP substrate was coated with various soft materials, namely, nCB, nOCB, SSY, and fluorinated dendrimer, by either spin-coating or a sandwiched-cell or solution-casting method, depending on the materials and observation tools (for specific experimental conditions, see the Experimental Section; Figure 1b). Thermotropic nCBs, nOCBs, and lyotropic SSY were used because the anchoring behavior of Controlling the molecular orientation of soft materials is one of the most important issues in physical and materials ...

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confidence: 99%

Ultrastrong Anchoring on the Periodic Atomic Grooves of Black Phosphorus

Kim

Jeong

Kwon

et al. 2016

Adv Materials Inter

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“…2(c). The DOP can be calculated from the following equation; DOP = (T 0 − T 90 )/(T 0 + T 90 )293940. Here, T 0 and T 90 mean the transmittances when the azimuthal angles are 0° and 90° to the polarization axis of the UV-vis polarizer, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, our research group successfully fabricated the coatable thin film polarizer by the polymer-stabilization of macroscopically oriented lyotropic chromonic liquid crystal (LCLC)28293031. The LCLC-based coatable polarizers stabilized by the photopolymerization of LCLC monomers exhibit high polarizabilities as well as excellent chemical and mechanical resistances.…”

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confidence: 99%

“…It is worth noticing that the LCLC-based coatable thin film is a E-type polarizer which transmits the extraordinary ray and extincts the ordinary ray, while the conventional polarizer using the stretched-polymer is a O-type polarizer which transmits the extraordinary ray and extincts the ordinary ray. Thus, the incident light polarized parallel to the long molecular axis of the LCLC molecule can transmit the polarizer29303132333435.…”

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Multifunctional Optical Thin Films Fabricated by the Photopolymerization of Uniaxially Oriented Lyotropic Liquid Crystal Monomers for Electro-Optical Devices

Choi

Yoon

et al. 2016

Sci Rep

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A multifunctional optical thin film (MOTF) is fabricated by coating the newly synthesized perylene-based reactive mesogen (PBRM) and stabilized by the subsequent photopolymerization. Based on the spectroscopic results combined with morphological observations, it is found that nematic liquid crystal (NLC) is aligned parallel to the molecular long axis of PBRM not only due to the long-range physical anchoring effect but also due to the short-range molecular physical interactions between alignment layer and NLC molecules. From the electro-optical properties of LC test cells fabricated with the PBRM MOTF, it is clearly demonstrated that the PBRM MOTF can work as the planar LC alignment layer as well as the in-cell coatable polarizer. The coatable PBRM MOTF from lyotropic chromonic reactive mesogens can pave a new way for the flexible optoelectronic devices.

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“…It is also possible to photopattern the color filter and polarizer by using selective photo irradiation through a photomask, which is required for the realization of 3D displays. Compared to previously reported polymerized thin films, 11,15 the new method provides a mono domain thin film. Hence the incident light does not scatter.…”

Section: Introductionmentioning

confidence: 99%

Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

2015

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We present a method to fabricate a thin film color filter based on a mixture of photo-polymerizable liquid crystal and chiral dopant. A chiral nematic liquid crystal layer reflects light for a certain wavelength interval ∆λ (= ∆n.P) with the period and ∆n the birefringence of the liquid crystal. The reflection band is determined by the chiral dopant concentration. The bandwidth is limited to 80nm and the reflectance is at most 50% for unpolarized incident light. The thin color filter is interesting for innovative applications like polarizer-free reflective displays, polarization-independent devices, stealth technologies, or smart switchable reflective windows to control solar light and heat. The reflected light has strong color saturation without absorption because of the sharp band edges. A thin film polarizer is developed by using a mixture of photo-polymerizable liquid crystal and color-neutral dye. The fabricated thin film absorbs light that is polarized parallel to the c axis of the LC. The obtained polarization ratio is 80% for a film of only 12 µm. The thin film polarizer and the color filter feature excellent film characteristics without domains and can be detached from the substrate which is useful for e.g. flexible substrates.

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A novel thin film polarizer from photocurable non-aqueous lyotropic chromonic liquid crystal solutions

Cited by 42 publications

References 14 publications

Ultrastrong Anchoring on the Periodic Atomic Grooves of Black Phosphorus

Ultrastrong Anchoring on the Periodic Atomic Grooves of Black Phosphorus

Multifunctional Optical Thin Films Fabricated by the Photopolymerization of Uniaxially Oriented Lyotropic Liquid Crystal Monomers for Electro-Optical Devices

Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

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