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Special Issue "Liquid Crystals"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 August 2009)

Special Issue Editor

Guest Editor
Prof. Dr. Kevin D. Belfield

College of Science and Liberal Arts, New Jersey Institute of Technology, 504 Cullimore Hall, 323 Dr. Martin Luther King Jr. Blvd Newark, NJ 07102
Website | E-Mail
Phone: +1 973-596-3676
Fax: +1 973-596-6063
Interests: multiphoton absorbing materials; two-photon photochemistry; in vivo and ex vivo two-photon fluorescence bioimaging; magnetic polymeric and sol-gel nanocomposites; site-specific fluorophore labeling; fluorescent-based sensors and bioimaging probes; photodynamic therapy agents; nanostructured functional organic and polymeric materials; two-photon based 3D high density optical data storage

Special Issue Information

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.

Prof. Dr. Kevin D. Belfield
Guest Editor

Submission

All papers should be submitted to materials@mdpi.com. 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 MDPI. Review manuscripts: Before writing their manuscripts, potential authors of review articles should forward the title and a short abstract to materials@mdpi.com. 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).

Keywords

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

Related Special Issue

Published Papers (15 papers)

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Research

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Open AccessArticle Directional Scattering of Semiconductor Nanoparticles Embedded in a Liquid Crystal
Materials 2014, 7(4), 2784-2794; doi:10.3390/ma7042784
Received: 27 February 2014 / Revised: 28 March 2014 / Accepted: 28 March 2014 / Published: 3 April 2014
Cited by 1 | PDF Full-text (510 KB) | HTML Full-text | XML Full-text
Abstract
Light scattering by semiconductor nanoparticles has been shown to be more complex than was believed until now. Both electric and magnetic responses emerge in the visible range. In addition, directional effects on light scattering of these nanoparticles were recently obtained. In particular, zero
[...] Read more.
Light scattering by semiconductor nanoparticles has been shown to be more complex than was believed until now. Both electric and magnetic responses emerge in the visible range. In addition, directional effects on light scattering of these nanoparticles were recently obtained. In particular, zero backward and minimum-forward scattering are observed. These phenomena are very interesting for several applications such as, for instance, optical switches or modulators. The strong dependence of these phenomena on the properties of both the particle and the surrounding medium can be used to tune them. The electrical control on the optical properties of liquid crystals could be used to control the directional effects of embedded semiconductor nanoparticles. In this work, we theoretically analyze the effects on the directional distribution of light scattering by these particles when the refractive index of a surrounded liquid crystal changes from the ordinary to the extraordinary configuration. Several semiconductor materials and liquid crystals are studied in order to optimize the contrast between the two states. Full article
(This article belongs to the Special Issue Liquid Crystals)
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Open AccessArticle Probing the Texture of the Calamitic Liquid Crystalline Dimer of 4-(4-Pentenyloxy)benzoic Acid
Materials 2010, 3(2), 827-840; doi:10.3390/ma3020827
Received: 22 December 2009 / Revised: 20 January 2010 / Accepted: 21 January 2010 / Published: 29 January 2010
Cited by 5 | PDF Full-text (5055 KB) | HTML Full-text | XML Full-text
Abstract
The liquid crystalline dimer of 4-(4-pentenyloxy)benzoic acid, a member of the n-alkoxybenzoic acid homologous series, was synthesized using potassium carbonate supported on alumina as catalyst. The acid dimer complex exhibited three mesophases; identified as nematic, smectic X1 and smectic X2. Phase transition
[...] Read more.
The liquid crystalline dimer of 4-(4-pentenyloxy)benzoic acid, a member of the n-alkoxybenzoic acid homologous series, was synthesized using potassium carbonate supported on alumina as catalyst. The acid dimer complex exhibited three mesophases; identified as nematic, smectic X1 and smectic X2. 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 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. Full article
(This article belongs to the Special Issue Liquid Crystals)
Open AccessArticle A Polarizer-Free Electro-Optical Switch Using Dye-Doped Liquid Crystal Gels
Materials 2009, 2(4), 1662-1673; doi:10.3390/ma2041662
Received: 3 September 2009 / Revised: 4 October 2009 / Accepted: 23 October 2009 / Published: 26 October 2009
Cited by 11 | PDF Full-text (1933 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate a polarizer-free electro-optical switch using dye-doped liquid crystal (LC) gels. The mechanism of dye-doped LC gels mainly involves the combination of polymer scattering and dye absorption. However, the domain size of polymer networks, dye concentration, LC concentration, and fabrication process can
[...] Read more.
We demonstrate a polarizer-free electro-optical switch using dye-doped liquid crystal (LC) gels. The mechanism of dye-doped LC gels mainly involves the combination of polymer scattering and dye absorption. However, the domain size of polymer networks, dye concentration, LC concentration, and fabrication process can all affect the phase separation process and thus result in dye-doped LC gels with different electro-optical performance. We have studied experimentally the factors which can affect the dye-doped LC gels. The potential applications for dye-doped LC gels are flexible displays and electrically tunable light shutters. Full article
(This article belongs to the Special Issue Liquid Crystals)
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Open AccessArticle Photo-Induced Phase Transitions to Liquid Crystal Phases: Influence of the Chain Length from C8E4 to C14E4
Materials 2009, 2(3), 1305-1322; doi:10.3390/ma2031305
Received: 28 August 2009 / Revised: 14 September 2009 / Accepted: 16 September 2009 / Published: 17 September 2009
Cited by 2 | PDF Full-text (987 KB) | HTML Full-text | XML Full-text
Abstract
Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i) with n =
[...] Read more.
Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i) with n = 8, 10, 12, 14; cyclohexane/H2O. We were interested in understanding the effect of chain length increase on the dynamics of transformation from the microemulsion phase to the liquid crystal phase. Applying light pump (pulse)/x-ray probe (pulse) techniques, we could demonstrate that entropy and diffusion control are the driving forces for the kind of phase transition investigated. Full article
(This article belongs to the Special Issue Liquid Crystals)
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Open AccessArticle Role of Lifshitz Invariants in Liquid Crystals
Materials 2009, 2(2), 674-698; doi:10.3390/ma2020674
Received: 5 May 2009 / Revised: 12 June 2009 / Accepted: 16 June 2009 / Published: 16 June 2009
PDF Full-text (351 KB) | HTML Full-text | XML Full-text
Abstract
The interaction between an external action and the order parameter, via a dependence described by a so-called Lifshitz invariant, is very important to determine the final configuration of liquid crystal cells. The external action can be an electric field applied to the bulk
[...] Read more.
The interaction between an external action and the order parameter, via a dependence described by a so-called Lifshitz invariant, is very important to determine the final configuration of liquid crystal cells. The external action can be an electric field applied to the bulk or the confinement due to free surfaces or cell walls. The Lifshitz invariant includes the order parameter in the form of an elastic strain. This coupling between elastic strains and fields, inserted in a Landau-Ginzburg formalism, is well known and gives rise to striction effects causing undulations in the director configuration. We want to discuss here the role of Lifshitz coupling terms, following an approach similar to that introduced by Dzyaloshinskii for magnetic materials. Case studies on nematics in planar and cylindrical cells are also proposed. Full article
(This article belongs to the Special Issue Liquid Crystals)
Open AccessArticle Focal Conic Stacking in Smectic A Liquid Crystals: Smectic Flower and Apollonius Tiling
Materials 2009, 2(2), 499-513; doi:10.3390/ma2020499
Received: 3 February 2009 / Revised: 16 April 2009 / Accepted: 20 April 2009 / Published: 22 April 2009
Cited by 14 | PDF Full-text (3558 KB) | HTML Full-text | XML Full-text
Abstract
We investigate two different textures of smectic A liquid crystals. These textures are particularly symmetric when they are observed at crossed polars optical microscopy. For both textures, a model has been made in order to examine the link between the defective macroscopic texture
[...] Read more.
We investigate two different textures of smectic A liquid crystals. These textures are particularly symmetric when they are observed at crossed polars optical microscopy. For both textures, a model has been made in order to examine the link between the defective macroscopic texture and the microscopic disposition of the layers. We present in particular in the case of some hexagonal tiling of circles (similar to the Apollonius tiling) some numeric simulation in order to visualize the smectic layers. We discuss of the nature of the smectic layers, which permit to assure their continuity from one focal conic domain to another adjacent one. Full article
(This article belongs to the Special Issue Liquid Crystals)
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Open AccessArticle Mesomorphic Behavior of Symmetrical and Unsymmetrical Azomethines with Two Imine Groups
Materials 2009, 2(1), 38-61; doi:10.3390/ma2010038
Received: 26 November 2008 / Revised: 3 February 2009 / Accepted: 5 February 2009 / Published: 6 February 2009
Cited by 17 | PDF Full-text (1079 KB) | HTML Full-text | XML Full-text
Abstract
Seven symmetrical azomethines with two imine groups (HC=N) were synthesized by condensation of the benzene-1,4-dicarboxaldehydewith five amines (first group: A1-A5) and of the 2,5-thiophenedicarboxaldehyde with two amines (second group: AT1-AT2). Additionally, two unsymmetrical azomethines were obtained by a two step condensation of benzene-1,4-dicarboxaldehydewith
[...] Read more.
Seven symmetrical azomethines with two imine groups (HC=N) were synthesized by condensation of the benzene-1,4-dicarboxaldehydewith five amines (first group: A1-A5) and of the 2,5-thiophenedicarboxaldehyde with two amines (second group: AT1-AT2). Additionally, two unsymmetrical azomethines were obtained by a two step condensation of benzene-1,4-dicarboxaldehydewith pyren-1-amine(1st step) (abbreviated hereinafter as AP1) and then AP1 was reacted with4-dodecylaniline or 4-hexadecylaniline (2nd step) (third group: AP1A-AP1B). Liquid crystalline properties of the azomethines were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and UV-vis spectroscopy in the function of temperature [UV-vis(T)]. The Wide-Angle X-ray Diffraction (WAXD) technique was used to probe the structural properties of the azomethines. Mesomorphic behavior was observed for symmetrical and unsymmetrical azomethines, obtained from the benzene-1,4-dicarboxaldehyde and symmetrical ones prepared from 2,5-thiophenedicarboxaldehyde and different amineshaving aliphatic chains. Based on the POM and DSC measurements the following mesophases were detected: nematic, smectic A, smectic C, smectic F (I), smectic G (J). Full article
(This article belongs to the Special Issue Liquid Crystals)
Open AccessArticle Liquid Crystalline π-Conjugated Copolymers Bearing a Pyrimidine Type Mesogenic Group
Materials 2009, 2(1), 22-37; doi:10.3390/ma2010022
Received: 9 December 2008 / Accepted: 12 January 2009 / Published: 16 January 2009
Cited by 8 | PDF Full-text (795 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
Phenylene-thiophene-based liquid crystalline π-conjugated copolymers bearing mesogenic groups as side chains were synthesized via a Stille polycondensation reaction and confirmed to exhibit a nematic liquid crystal phase at appropriate temperatures. The formation of a nematic phase, but not a smectic phase indicates cooperation
[...] Read more.
Phenylene-thiophene-based liquid crystalline π-conjugated copolymers bearing mesogenic groups as side chains were synthesized via a Stille polycondensation reaction and confirmed to exhibit a nematic liquid crystal phase at appropriate temperatures. The formation of a nematic phase, but not a smectic phase indicates cooperation of the main chain and side chain in the formation of a nematic main-chain/side-chain liquid crystal phase. The generation of polarons in the main chain as charge carriers during in-situ vapor doping of iodine is confirmed to increase with a doping progresses, exhibiting Dysonian paramagnetic behavior typical of conductive polymers. Full article
(This article belongs to the Special Issue Liquid Crystals)

Review

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Open AccessReview Carbon Nanotube-Reinforced Thermotropic Liquid Crystal Polymer Nanocomposites
Materials 2009, 2(4), 1955-1974; doi:10.3390/ma2041955
Received: 5 October 2009 / Revised: 4 November 2009 / Accepted: 5 November 2009 / Published: 26 November 2009
Cited by 15 | PDF Full-text (717 KB) | HTML Full-text | XML Full-text
Abstract
This paper focuses on the fabrication via simple melt blending of thermotropic liquid crystal polyester (TLCP) nanocomposites reinforced with a very small quantity of modified carbon nanotube (CNT) and the unique effects of the modified CNT on the physical properties of the nanocomposites.
[...] Read more.
This paper focuses on the fabrication via simple melt blending of thermotropic liquid crystal polyester (TLCP) nanocomposites reinforced with a very small quantity of modified carbon nanotube (CNT) and the unique effects of the modified CNT on the physical properties of the nanocomposites. The thermal, mechanical, and rheological properties of modified CNT-reinforced TLCP nanocomposites are highly dependent on the uniform dispersion of CNT and the interactions between the CNT and TLCP, which can be enhanced by chemical modification of the CNT, providing a design guide of CNTreinforced TLCP nanocomposites with great potential for industrial uses. Full article
(This article belongs to the Special Issue Liquid Crystals)
Open AccessReview Liquid Crystalline Behavior and Related Properties of Colloidal Systems of Inorganic Oxide Nanosheets
Materials 2009, 2(4), 1734-1761; doi:10.3390/ma2041734
Received: 29 August 2009 / Revised: 16 October 2009 / Accepted: 27 October 2009 / Published: 29 October 2009
Cited by 25 | PDF Full-text (773 KB) | HTML Full-text | XML Full-text
Abstract
Inorganic layered crystals exemplified by clay minerals can be exfoliated in solvents to form colloidal dispersions of extremely thin inorganic layers that are called nanosheets. The obtained “nanosheet colloids” form lyotropic liquid crystals because of the highly anisotropic shape of the nanosheets. This
[...] Read more.
Inorganic layered crystals exemplified by clay minerals can be exfoliated in solvents to form colloidal dispersions of extremely thin inorganic layers that are called nanosheets. The obtained “nanosheet colloids” form lyotropic liquid crystals because of the highly anisotropic shape of the nanosheets. This system is a rare example of liquid crystals consisting of inorganic crystalline mesogens. Nanosheet colloids of photocatalytically active semiconducting oxides can exhibit unusual photoresponses that are not observed for organic liquid crystals. This review summarizes experimental work on the phase behavior of the nanosheet colloids as well as photochemical reactions observed in the clay and semiconducting nanosheets system. Full article
(This article belongs to the Special Issue Liquid Crystals)
Open AccessReview Development of Highly Soluble Anthraquinone Dichroic Dyes and Their Application to Three-Layer Guest-Host Liquid Crystal Displays
Materials 2009, 2(4), 1636-1661; doi:10.3390/ma2041636
Received: 31 August 2009 / Revised: 9 October 2009 / Accepted: 21 October 2009 / Published: 23 October 2009
Cited by 25 | PDF Full-text (531 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
The relationships between molecular structures and properties of anthraquinone dichroic dyes were studied and dyes with large solubilities and dichroic ratios were developed. The yellow anthraquinone dye behaves as a quencher of the coumarin dye, and the mixture has a large absorption coefficient
[...] Read more.
The relationships between molecular structures and properties of anthraquinone dichroic dyes were studied and dyes with large solubilities and dichroic ratios were developed. The yellow anthraquinone dye behaves as a quencher of the coumarin dye, and the mixture has a large absorption coefficient without fluorescence. These technologies can enlarge the color reproduction area of three-layer guest-host liquid crystal displays (GHLCDs) 1.6-fold. The performances of the prototype reflective three-layer GH-LCDs are as follows: the white state luminous reflectance is 43% and the contrast is 5.3, indicating that they are promising candidates for portable information systems with full-color images. Full article
(This article belongs to the Special Issue Liquid Crystals)
Figures

Open AccessReview Polymers Comprising Cholesterol: Synthesis, Self-Assembly, and Applications
Materials 2009, 2(2), 636-660; doi:10.3390/ma2020636
Received: 5 May 2009 / Revised: 21 May 2009 / Accepted: 25 May 2009 / Published: 2 June 2009
Cited by 38 | PDF Full-text (937 KB) | HTML Full-text | XML Full-text
Abstract
This article reviews the current status of self-assembling liquid crystalline polymers comprising cholesterol. This article will focus on synthesis, structure-property relationships and strategies to direct ordering and packing of meso- and nanostructures of cholesterol polymers in the neat- or melt state and in
[...] Read more.
This article reviews the current status of self-assembling liquid crystalline polymers comprising cholesterol. This article will focus on synthesis, structure-property relationships and strategies to direct ordering and packing of meso- and nanostructures of cholesterol polymers in the neat- or melt state and in solution. The applications of these self-assembled structures will be presented. Full article
(This article belongs to the Special Issue Liquid Crystals)
Open AccessReview Impact of Liquid Crystals in Active and Adaptive Optics
Materials 2009, 2(2), 549-561; doi:10.3390/ma2020549
Received: 3 February 2009 / Revised: 24 April 2009 / Accepted: 11 May 2009 / Published: 12 May 2009
Cited by 9 | PDF Full-text (257 KB) | HTML Full-text | XML Full-text
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 continued progress in this field.
[...] Read more.
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 continued progress in this field. 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 thus the development of new useful tools for Active and Adaptive Optics. Full article
(This article belongs to the Special Issue Liquid Crystals)
Figures

Open AccessReview Side-chain Liquid Crystal Polymers (SCLCP): Methods and Materials. An Overview
Materials 2009, 2(1), 95-128; doi:10.3390/ma2010095
Received: 5 February 2009 / Revised: 3 March 2009 / Accepted: 9 March 2009 / Published: 11 March 2009
Cited by 21 | PDF Full-text (279 KB) | HTML Full-text | XML Full-text
Abstract
This review focuses on recent developments in the chemistry of side chain liquid crystal polymers. It concentrates on current trends in synthetic methods and novel, well defined structures, supramolecular arrangements, properties, and applications. The review covers literature published in this century, apart from
[...] Read more.
This review focuses on recent developments in the chemistry of side chain liquid crystal polymers. It concentrates on current trends in synthetic methods and novel, well defined structures, supramolecular arrangements, properties, and applications. The review covers literature published in this century, apart from some areas, such as dendritic and elastomeric systems, which have been recently reviewed. Full article
(This article belongs to the Special Issue Liquid Crystals)
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Other

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Open AccessCorrection Correction: Goto, H. et al. Liquid Crystalline π-Conjugated Copolymers Bearing a Pyrimidine Type Mesogenic Group. Materials 2009, 2, 22-37
Materials 2012, 5(1), 156; doi:10.3390/ma5010156
Received: 11 October 2011 / Accepted: 9 January 2012 / Published: 9 January 2012
PDF Full-text (177 KB) | HTML Full-text | XML Full-text
Abstract We found an error in the Scheme 1 in our paper published in Materials [1]. [...] Full article
(This article belongs to the Special Issue Liquid Crystals)

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