scholarly journals Enhancement of Spontaneous Polarization and Acid Vapor-Induced Polymerization in the Thin-Film States of Phenylterthiophene Derivative Bearing a Cyclotetrasiloxane Ring

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 983
Author(s):  
Jumpei Nakagawa ◽  
Atsushi Seki ◽  
Masahiro Funahashi
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Liquid Crystal ◽  
Spontaneous Polarization ◽  
Liquid Crystalline ◽  
Substrate Surface ◽  
Helical Structure ◽  
Polymerization Process ◽  
Ferroelectric Liquid Crystal ◽  
Acid Vapor

We have achieved the measurement of spontaneous polarization of spin-coated thin films of a ferroelectric liquid crystal based on a phenylterthiophene skeleton. Uniaxially aligned spin-coated films with a thickness of 100 nm were prepared by the friction transfer method. The spontaneous polarization of the spin-coated films was measured by the Sawyer–Tower method and polarization inversion current technique under the application of triangular-wave bias. These measurements revealed the spontaneous polarization of 50 nC cm−2 in the thin-film state which is 1.5 times larger than the value of 35 nC cm−2 in the bulk state. This result should be attributed to the strong anchoring of the liquid-crystalline molecules on the substrate surface and the inhibition of polarization relaxation caused by the formation of the helical structure. Moreover, insolubilization of the thin films was carried out by an in situ ring-opening polymerization induced by acid vapors. The molecular alignment in the thin films of the ferroelectric liquid crystal was retained during the polymerization process.

Observations on the growth of YBa2Cu3O7-δ thin films on MgO by pulsed-laser ablation

1991 ◽  
Vol 49 ◽  
pp. 1068-1069
Author(s):  
M. Grant Norton ◽  
C. Barry Carter
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Laser Ablation ◽  
Substrate Surface ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Laser Ablation Process ◽  
Deposition Parameters

Pulsed-laser ablation has been widely used to produce high-quality thin films of YBa2Cu3O7-δ on a range of substrate materials. The nonequilibrium nature of the process allows congruent deposition of oxides with complex stoichiometrics. In the high power density regime produced by the UV excimer lasers the ablated species includes a mixture of neutral atoms, molecules and ions. All these species play an important role in thin-film deposition. However, changes in the deposition parameters have been shown to affect the microstructure of thin YBa2Cu3O7-δ films. The formation of metastable configurations is possible because at the low substrate temperatures used, only shortrange rearrangement on the substrate surface can occur. The parameters associated directly with the laser ablation process, those determining the nature of the process, e g. thermal or nonthermal volatilization, have been classified as ‘primary parameters'. Other parameters may also affect the microstructure of the thin film. In this paper, the effects of these ‘secondary parameters' on the microstructure of YBa2Cu3O7-δ films will be discussed. Examples of 'secondary parameters' include the substrate temperature and the oxygen partial pressure during deposition.

Epitaxial Growth of Sr0.3Ba0.7Nb2O6 Thin Films Prepared by Sol-Gel Process

1999 ◽  
Vol 606 ◽  
Author(s):  
Keishi Nishio ◽  
Jirawat Thongrueng ◽  
Yuichi Watanabe ◽  
Toshio Tsuchiya
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Epitaxial Growth ◽  
Raw Materials ◽  
Substrate Surface ◽  
Sol Gel ◽  
Tungsten Bronze ◽  
Monomethyl Ether ◽  
Tetragonal Tungsten Bronze ◽  
Sol Gel Process

AbstructWe succeeded in the preparation of strontium-barium niobate (Sr0.3Ba0.7Nb2O6 : SBN30)that have a tetragonal tungsten bronze type structure thin films on SrTiO3 (100), STO, or La doped SrTiO3 (100), LSTO, single crystal substrates by a spin coating process. LSTO substrate can be used for electrode. A homogeneous coating solution was prepared with Sr and Ba acetates and Nb(OEt)5 as raw materials, and acetic acid and diethylene glycol monomethyl ether as solvents. The coating thin films were sintered at temperature from 700 to 1000°C for 10 min in air. It was confirmed that the thin films on STO substrate sintered above 700°C were in the epitaxial growth because the 16 diffraction spots were observed on the pole figure using (121) reflection. The <130> and <310> direction of the thin film on STO were oriented with the c-axis in parallel to the substrate surface. However, the diffraction spots of thin film on LSTO substrate sintered at 700°C were corresponds to the expected pattern for (110).

scholarly journals Engineering Achiral Liquid Crystalline Polymers for Chiral Self-Recovery

2021 ◽  
Vol 22 (21) ◽  
pp. 11980
Author(s):  
Tengfei Miao ◽  
Xiaoxiao Cheng ◽  
Yilin Qian ◽  
Yaling Zhuang ◽  
Wei Zhang
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Uv Light ◽  
Helical Structure ◽  
Side Chain ◽  
Liquid Crystal Polymers ◽  
Polymeric Liquid ◽  
Crystalline Polymers ◽  
Liquid Crystal System ◽  
And Storage

Flexible construction of permanently stored supramolecular chirality with stimulus-responsiveness remains a big challenge. Herein, we describe an efficient method to realize the transfer and storage of chirality in intrinsically achiral films of a side-chain polymeric liquid crystal system by combining chiral doping and cross-linking strategy. Even the helical structure was destroyed by UV light irradiation, the memorized chiral information in the covalent network enabled complete self-recovery of the original chiral superstructure. These results allowed the building of a novel chiroptical switch without any additional chiral source in multiple types of liquid crystal polymers, which may be one of the competitive candidates for use in stimulus-responsive chiro-optical devices.

Dot Inversion Spontaneous Polarization Structure in the Half-V-shaped Switching Ferroelectric Liquid Crystal Mode

2003 ◽  
Vol 42 (Part 1, No. 2A) ◽  
pp. 554-558
Author(s):  
Yasufumi Asao ◽  
Hideki Yoshinaga ◽  
Hideo Mori ◽  
Hirohide Munakata ◽  
Ryuichiro Isobe ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Spontaneous Polarization ◽  
Ferroelectric Liquid Crystal ◽  
Polarization Structure

Tunable topographical cellulose matrices for electro-optical liquid crystal cells

2006 ◽  
Vol 14 (4) ◽  
Author(s):  
I. Costa ◽  
P. Almeida ◽  
D. Filip ◽  
J. Figueirinhas ◽  
M. Godinho
Keyword(s):  
Thin Films ◽  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Cellulose Derivatives ◽  
Free Standing ◽  
Casting Technique ◽  
Solvent Vapour ◽  
Preparation Conditions ◽  
And Control ◽  
Crystal Cells

AbstractIn this work we have used acetoxypropylcellulose (APC) to produce free standing solid films (∼60 μm) that were used for assembling electro-optical devices. Thin films were obtained from concentrated lyotropic solutions of cellulose derivatives. Induced by the cast and shearing preparation conditions wrinkles and band textures can be observed in their free-surface plane. In order to eliminate and control these textures we used a process similar to that introducted in literature [1] which consists of storing the films in the same solvent-vapour atmosphere as the solution system. Lyotropic APC liquid crystalline solutions in dymethylacetamide (DMA) with crosslinker were prepared, thin films were obtained by using a shear/casting technique and stored in the solvent-vapour atmosphere until a planar structure was achieved. The dried crosslinked films were analyzed by optical polarised microscopy (POM) and scanning electron microscopy (SEM). The films with different topographies were used to produce optical cells composed by the cellulose derivative film covered on both free surfaces by a layer of the nematic liquid crystal E7 and placed between two transparent conducting substrates. The electro-optical properties of these cells were obtained.

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