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,

Since the first reported observation of a liquid crystalline behavior by the Austrian botanist Friedrich Reinitzer in 1888, liquid crystals have attracted immense scientific interest. Scientists have been drawn to the study of liquid crystals by both their unusual mesomorphic properties, being intermediate between the solid, crystalline state and the isotropic liquid phase, and the relative aesthetics attained upon observing the often spectacular mesophases between cross polarizers on an optical microscope. Over the past three to four decades, a number of unique properties exhibited by liquid crystalline materials in response to external stimuli have been exploited in a number of important technologies. For example, ferroelectric liquid crystals have been key components in the digital age, leading a revolution in display technology. Thermotropic liquid crystalline materials continue to find their place in numerous products including the healthcare field. Lyotropic liquid crystalline polymers have propelled the field of high strength, light weight materials for a number of military and civilian applications, including their important contribution in body armor. It is fitting that we have special issues in the Journal of Molecular Sciences and Materials dedicated to this still very intriguing class of materials that promises to continue to be an integral part of emerging technologies.

Kevin D. Belfield, Ph.D.
Guest Editor

Related Special Issue

Liquid Crystals in the International Journal of Molecular Sciences

Submission

All papers should be submitted to materials@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. Materials is an international peer-reviewed quarterly journal published by Molecular Diversity Preservation International. Review manuscripts: Before writing their manuscripts, potential authors of review articles should forward the title and a short abstract to materials@mdpi.org. We will then provide feedback on the suitability of the topic.

Article Processing Charges (APC)

Article Processing Charges (APC) will be waived for well prepared manuscripts of invited papers. For the first two volumes of this new journal the APC are of 300 CHF (or 550 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

Feature Papers

Type of Paper: Article
Title: Synthesis, Characterization and Texture Study of the Calamitic Liquid Crystalline Dimer, 4-(4-Pentenyloxy)benzoic Acid
Authors: Kevin D. Belfield ^{1, 2,}* and Maher A. Qaddoura ¹
Affiliations: ¹ Department of Chemistry and ² CREOL, The College of Optics and Photonics, University of Central Florida, P.O. Box 162366, Orlando, FL 32816-2366, USA
* Author to whom correspondence should be addressed; E-mail: belfield@mail.ucf.edu
Abstract: The liquid crystalline dimer, 4-(4-pentenyloxy) benzoic acid, a member of the n-alkoxybenzoic acid homologous series, was synthesized using potassium carbonate supported on alumina as a catalyst. The complex exhibited three liquid crystalline phases. Phase transition temperatures and the corresponding enthalpies were recorded using differential scanning calorimetry upon both heating and cooling. The mesophases were identified by detailed texture observations by variable temperature polarized light microscopy. The acid dimmer complex exhibited three mesophases; identified as nematic, smectic x1 and smectic x2. The nematic phase was distinguished by a fluid schlieren texture and defect points (four and two brushes) while the smectic phases were distinguished by rigid marble and mosaic textures, respectively.

Regular Papers

Type of Paper: Review
Title: Impact of Liquid Crystals in Active and Adaptive Optics
Author: Justo Arines
Affiliation: Departamento de Fisica Aplicada (area de optica), Facultad de Ciencias, Universidad de Zaragoza, Spain. E-mail: fajap@unizar.es
Abstract: Active and dynamic modulation of light has been one of major contributions of liquid crystals to Optics. The spectrum of application range from signposting panels to high resolution imaging. The development of new materials is the key to continue with the progress. To promote this we will present in this paper recent uses of liquid crystals as active or adaptive modulators of light. Besides we will reflect on their current limitations. We expect with this to contribute to the progress in the field of liquid crystals and so the development of new useful tools for Active and Adaptive Optics.

Type of Paper: Article
Title: Solid-state Polarized Light Emitters for Display Applications and Emergence of Semipolar-oriented III-nitride Optoelectronic Devices
Authors: Hisashi Masui
Affiliations: Interdisciplinary Center for Wide Band-Gap Semiconductors and Solid State Lighting & Display Center, University of California, Santa Barbara, CA 93106-5055, USA. E-mail: masui@engineering.ucsb.edu
Abstract: The solid-state lighting technology is expected to replace the vacuum-based lighting technology. Familiar examples may be light-emitting diode (LED) traffic lights and white LED backlighting in liquid-crystal displays. The former has eliminated color filters that were used with conventional incandescent lamps. The latter still uses polarization filters, which may be eliminated by using polarized LEDs: Recent progress in GaN-based LEDs enables us to obtain polarized light. The article reports preliminary experiments showing efficiency improvements by employing such polarized LEDs and discusses prospects in polarized primary-color emitters, green diode lasers, yellow light sources, and waveguide slabs.

Type of Paper: Article
Title: Towards Novel Banana-shaped Triple Helical Liquid Crystals by Metal Coordination
Authors: P. Iqbal,M. Manickam *, L. J. Childs, M. J. Hannonand J. A. Preece
Affiliations: School of Chemistry, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. Tel. +44 (0) 121 414 4395; Fax: +44 (0)121 414 4403; E-mail: M.Manickam@bham.ac.uk
Abstract: The synthesis of a series of banana-shaped mesogenic structures has been carried out, in which the bend unit is formed by the 4, 4’-methylenedianiline or 3, 3’-methylenedianiline core bearing two symmetric pyridylimine linkages to di- and tri- alkoxyphenylester moieties on the side arms. The molecules as well as providing an elongated aromatic central core associated with LC molecules, also provide binding sites for metals. The methylenedianiline spacer incorporates phenylene groups that sterically prevent the two binding sites from co-ordinating to a single metal centre and the central methylene unit introduces enhanced flexibility into the ligand backbone. Thermal analysis of the final compounds has been carried out in order to investigate the phase properties of these materials. The 4, 4’-methylenedianiline core upon metal coordination expected to form a rod-like structure, whereas the 3, 3’-methylenedianiline core forms a novel bent triple stranded helicate structure. Such a metal containing mesogenic structure conjures up potential application of magnetic LC phases.

Type of Paper: Review
Title: Liquid Crystals in Chromatography
Authors: J. Oszczudłowski, M. Marcinkowska and Z. Witkiewicz *
* Author to whom correspondence should be addressed; E-mail: witkiew@wp.pl
Abstract: The ordering of thermotropic molecules of nematic, smectic and cholesteric liquid crystals has been used in, among others, gas and liquid chromatography. Monomolecular and polymeric liquid crystals as well as those in the form of complexes with transition metals are used as highly selective stationary phases to separate mostly isomers of a different type. Interactions between liquid-crystalline stationary phases and chromatographed substances are of a stereospecific nature. Using these phases, it is possible to separate e.g. mixtures of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and polychlorinated dioxins. Separation properties and thermal stability of liquid-crystalline stationary phases depend on the molecular structure of a liquid crystal, the type of mesophase and its temperature range. Liquid crystals can also be used to visualize thin-layer chromatograms.