Special Issue "Liquid Crystals"

Guest Editor
Prof. Dr. Kevin D. Belfield
Department of Chemistry and CREOL, The College of Optics and Photonics, University of Central Florida, P.O. Box 162366, Orlando, FL 32816-2366, USA
E-Mail:
Interests: nonlinear optical materials; photonic materials; multiphoton absorbing materials; photochemistry; photophysics; two-photon fluorescence imaging; fluorescence lifetime imaging microscopy (FLIM); functional polymers and organic composites; supramolecular materials

Dear Colleagues,

Related Special Issue

Liquid Crystals in Materials

Submission

All papers should be submitted to ijms@mdpi.org. To be published continuously until the deadline and papers will be listed together at the special issue website.

Submitted papers should not have been published previously, nor be under consideration for publication elsewhere. All papers are refereed through a peer-review process. A guide for authors is available on the Instructions for Authors page. The International Journal of Molecular Sciences is an international peer-reviewed monthly journal published by Molecular Diversity Preservation International.

Open Access publication fees are 800 CHF per paper. English correction fees and/or formatting fees (250 CHF) will be added in certain cases (1050 CHF per paper for those papers that require extensive additional formatting and/or English corrections).

• liquid crystal
• mesogen
• mesomorphic
• thermotropic
• lyotropic
• smectic
• nematic
• liquid crystalline polymers
• cholesteric

Type of Paper: Article
Title: Liquid Crystal - Carbon Nanotubes Mixtures
Authors: Vlad Popa-Nita ¹, Paul van der Schoot ² and Samo Kralj ³
Affiliations: ¹ Faculty of Physics, University of Bucharest, P. O. Box MG-11, Bucharest 077125, Romania. E-mail: v.popanita@gmail.com
² Department of Applied Physics, Eindhoven University of Technology, P. O. Box 513, 5600 MB Eindhoven, The Netherlands
³ Laboratory Physics of Complex Systems, Faculty of Natural Science and Mathematics, University Of Maribor, Koroska 160, 2000 Maribor, Slovenia and Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Abstract: The self-organizing properties of nematic liquid crystals can be used to efficiently align carbon nanotubes dispersed in them. The phase ordering of the binary liquid crystal - carbon nanotubes mixture is analyzed as a function of concentration and temperature. Using phenomenological approaches two coupling limits are studied: (i) weak anchoring limit where the alignment is caused by the coupling of essentially unperturbed nematic fluid with the anisotropic interfacial tension of the nanotubes and (ii) strong anchoring limit where the nematic ordering around nanotubes is strongly perturbed. We find that the degree of ordering of the nanorods is enslaved by the properties of the host liquid and that it can be tuned by increasing or decreasing the temperature or their concentration.

Type of Paper: Review
Title: Phase Transitions in Liquid Crystals
Authors: Vlad Popa-Nita ¹ and Samo Kralj ²
Affiliations: 1 Faculty of Physics, University of Bucharest, P. O. Box MG-11, Bucharest 077125, Romania. E-mail: v.popanita@gmail.com
2 Laboratory Physics of Complex Systems, Faculty of Natural Science and Mathematics, University Of Maribor, Koroska 160, 2000 Maribor, Slovenia and Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Abstract: In the first chapter (entitled Phase transition in liquid crystals – a brief introduction), after a brief introduction into the field of liquid crystals which includes classification, characterization of the main types, and the definition of the order parameters, we present the microscopic theories as well as the phenomenological Landau- de Gennes theory of nematic – isotropic and nematic-smectic A phase transition. In the last section of the chapter the interface dynamics is discussed. We present the two model of solidification of a pure substance from its melt: the sharp interface model and the phase field model.
In the second chapter (entitled Influence of an external random field on phase transition in liquid crystals) we consider binary systems A+B, where A stands for a liquid crystal phase. As a component B either various nanoparticles or porous matrices are chosen, which enforce to a liquid crystal phase a random field-type disorder. In such systems phase behavior reflects the interplay among bulk liquid crystals properties, interactions at the A-B interface, disorder and finite size effects. Phase behavior is discussed as a function of several control parameters. We focus to universal features, which applies also to other systems, where a phase or structure of A is reached via a continuous symmetry breaking phase transition. We analyze applicability of the Imry-Ma theorem, the Kibble-Zurek mechanism, and slave-master mechanism in these systems.
In the third chapter a theoretical phase diagram of a ternary mixture composed by liquid crystal, colloids and impurities is presented. The experimental results on mixtures of thermotropic liquid crystals with spherical poly(methyl methacrilate) particles support the hypothesis that a third component, alkane remnants slowly liberated from the particles, plays a crucial role. A theoretical model, based on the phenomenological Landau-de Gennes, Carnahan-Starling, and hard-sphere crystal theories, is developed to describe the continuous phase transition in a ternary nematic-colloid-impurity mixture.

Type of Paper: Article
Title: In-TFT-Array-Process Micro Defect Inspection Using Nonlinear Principal Component Analysis
Authors: Yi-Hung Liu ^1,*, Chi-Kai Wang ¹, Yung Ting ¹, Ching-Shun Chen ² and Jih-Shang Hwang ³
Affiliations: ¹ Department of Mechanical Engineering, Chung Yuan Christian University, Chungli, 320, Taiwan
² Mechanical and Systems Research Laboratories, Industrial Technology Research Institute (ITRI), Hsinchu, Taiwan
³ Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung, 202, Taiwan
* Author to whom correspondence should be addressed; E-mail: lyh@cycu.edu.tw; Tel. +886-3-2654306; Fax: +886-3-2654399
Abstract: Defect inspection plays a critical role in thin film transistor liquid crystal display (TFT-LCD) manufacturing, and has received much attention in the field of automatic optical inspection (AOI). Previously, most focuses were put on the problems of macro-scale Mura-defect detection in cell process. However, it has recently been found that the defects which substantially influence the yield rate of LCD panels are actually those in TFT array process, which is the first process in TFT-LCD manufacturing. There are various defects in this process and their sizes are too small to observe in general. Defect inspection in TFT array process is therefore considered a difficult task. This paper presents a novel inspection scheme based on kernel principal component analysis (KPCA) algorithm, which is a nonlinear version of the well-known PCA algorithm. The inspection scheme can not only detect the defects from the images captured from the surface of LCD panels, but also recognize the types of the detected defects automatically. Results, carried on real images provided by a LCD manufacturer in Taiwan, indicate that the KPCA-based defect inspection scheme is able to obtain a defect detection rate of over 98% and a high defect classification rate of over 96%. More importantly, the inspection time is less than 1 second for one input image.
Keywords: TFT-LCD manufacturing, TFT array process, automatic optical inspection (AOI), defect inspection, kernel principal component analysis (KPCA).

Type of Paper: Review
Title: The Photonic Applications of Light-Controllable Liquid Crystal
Authors: Vincent K. S. Hsiao
Affiliations: Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, No 1, University Rd. Puli, Nantou Hsien, Taiwan 54561; E-mail: kshsiao@ncnu.edu.tw; Tel. 886-49-291-0960 ext. 4907; Fax: 886-49-291-2434
Abstract: This review focuses on the recent progresses of photonic applications using light-controllable liquid crystal (LC). Under the stimulus of external light the LC mixture changes its average refractive index (RI) that have found useful in different photonic devices. The modulation of RI is triggered by the trans-cis photoisomerization of the doped azobenzene molecule. The review will be valuable for those who are interested to extend their field of studying molecular science into applied photonics.