Prediction of the Clearing Temperatures of a Series of Liquid Crystals from Molecular Structure

and, Stephen R. Johnson; Jurs, Peter C.

doi:10.1021/cm980674x

Cited by 36 publications

(28 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…From these molecular descriptors, quantitative structure–activity relationships (QSAR)114 can be derived. This has recently been applied for the prediction of clearing temperatures for a number of liquid crystals 115. However, the variation in chemical structure must not be too large and the properties of structures not radically different from those used in the training set, otherwise the properties will probably not be predicted correctly.…”

Section: Tools For the Rational Design Of Liquid Crystalsmentioning

confidence: 99%

Nematic Liquid Crystals for Active Matrix Displays: Molecular Design and Synthesis

Kirsch

Bremer

2000

Angew. Chem. Int. Ed.

410

254

View full text Add to dashboard Cite

Substances forming calamitic mesophases have been known for more than 100 years but only the recent, rapid advance in active matrix liquid crystal display (AM‐LCD) technology helped these materials to achieve the crucial position in flat panel display technology they hold today. Due to their high contrast, large viewing angle, and rapid switching times, modern AM‐LCDs offer a superior picture quality even compared to conventional cathode ray tubes. Their flatness, low weight, and low energy consumption render them the technology of choice for all kinds of portable devices. Some of the future promises of AM‐LCD technology are centered around the development of liquid crystalline materials for the different subtypes of active matrix applications. This development is aimed, on the one hand, towards improved electrooptical and viscoelastic properties; on the other hand, the increasing performance of LCDs leads to extremely stringent reliability demands on the liquid crystals. Responding to these high standards of performance and quality, most liquid crystals for contemporary AM‐LCD applications are multiply fluorinated compounds with very high purities, as is typical for materials used in the electronics industry. The synthesis of these superfluorinated materials (SFMs) often requires specialized methods, which, in several cases, had to be introduced for the first time into the canon of industrial production. The immense market pressure, as well as the rapid advance of AM‐LCD technology on the side of the display manufacturers, urges an increasing pace of the materials development. This demand for new materials can no longer be fulfilled by conventional trial‐and‐error approaches. As in the pharmaceutical industry, in the search for new, superior liquid crystals, the purely empirical methods are increasingly supported by a rational design based on computational methods.

show abstract

Section: Tools For the Rational Design Of Liquid Crystalsmentioning

confidence: 99%

Nematic Liquid Crystals for Active Matrix Displays: Molecular Design and Synthesis

Kirsch

Bremer

2000

Angew. Chem. Int. Ed.

410

254

View full text Add to dashboard Cite

show abstract

“…Zusätzlich zu diesen hauptsächlich qualitativen Aspekten ist auch eine Berechnung geometrischer und elektronischer Strukturparameter möglich. [115] Die Unterschiede in der chemischen Struktur dürfen allerdings nicht zu groû sein, und die Eigenschaften von Substanzen, deren Struktur sich drastisch von denen des ¹training setª unterscheidet, lassen sich wahrscheinlich nicht korrekt vorhersagen. Kürzlich wurde dies auf die Vorhersage von Klärtemperaturen einer Reihe von Flüssigkristallen angewendet.…”

Section: Instrumentarium Für Das Rationale Design Von Flüssigkristallenunclassified

Nematische Flüssigkristalle für Aktiv-Matrix-Displays: Design und Synthese

Kirsch

Bremer

2000

Angewandte Chemie

View full text Add to dashboard Cite

EinführungInnerhalb nur weniger Jahre sind Flüssigkristall-Anzeigegeräte (LCDs) zu einem nahezu unverzichtbaren Teil unseres täglichen Lebens geworden. Weltweit wurden 1999 mehr als zwei Milliarden LCDs hergestellt. [1] Die Hälfte davon waren kleine, einfarbige Anzeigevorrichtungen für Uhren und Videospiele. Ein bis jetzt noch kleinerer, aber rasch wach-sender Anteil an dieser Gesamtmenge sind Farbdisplays mit hohem graphischem Auflösungsvermögen. Das vielleicht bekannteste Gerät dieser Art mit hohem Informationsgehalt ist der Desktop-PC-Monitor (hiervon wurden 1999 ca. 3.6 Millionen hergestellt, die meisten davon waren 15-Zoll-Bildschirme, d. h. 37.5 cm in der Diagonale), der mittlerweile zu einer ernsthaften Konkurrenz für den Monitor mit der schon lange etablierten Kathodenstrahlröhre (CRT) geworden ist. Nachdem man die schwierigsten Hürden auf dem Weg zu gröûeren Bildschirmen überwunden hat, haben die Displayhersteller als nächstes strategisches Ziel den flachen TV-Wandbildschirm anvisiert. Dieses Ziel wird man gewiss innerhalb der ersten Hälfte dieses Jahrzehnts erreicht haben.Die meisten dieser besonders hochwertigen Displays funktionieren auf der Grundlage der Aktiv-Matrix-Technologie, [2,3] bei der jedes Bildelement (¹Pixelª) einzeln über einen auf dem Displayglas integrierten Dünnfilmtransistor (thin film transistor, TFT) angesteuert wird. Die Hauptkomponenten eines LCD sind das mit Indium-Zinn-Oxid (ITO) als transparentem Elektrodenmaterial beschichtete Glas, Polari-

show abstract

“…The foremost example is probably the prediction of the nematic ± isotropic (NI) transition temperature T NI , a crucial element in the design of viable LC display materials that have to exist and operate in a certain temperature range, that is now tackled empirically. [22,23] The task is far from trivial since even small changes of structure can dramatically alter T NI .A classical demonstration is the so called ™odd ± even∫ effect, which corresponds to large alternation in properties and in mesophase transition temperatures, in particular for homologous series containing an n-alkyl chain, as n varies from even to odd. Examples of this effect have been known, in particular from the work of Gray and co-workers [24,25] and in Table 1 we report one such case for phenyl alkyl-4-(4'-cyanobenzylidene)aminocinnamates.…”

mentioning

confidence: 99%

Can Nematic Transitions Be Predicted By Atomistic Simulations? A Computational Study of The Odd–Even Effect

2004

View full text Add to dashboard Cite

Computer simulations at the atomistic level are often called realistic as they offer, in principle, the possibility of reproducing in full the properties of a molecular system. Unfortunately, the number of atomic centers for molecules forming liquid-crystalline phases is normally so large, and correspondingly the number of molecules considered so low, that the proof of true realism, for example, the approximate reproduction of transition temperatures and of the relevant observables (such as order parameters together with their temperature dependence) has to our knowledge never been given to date. This is understandable in view of the complexity of liquid crystal molecules and probably depends on at least three issues: interaction potentials, sample size, and equilibration time. The force fields available have not been developed to reproduce liquid crystal properties, and only recently have some recommendations on the most appropriate choice amongst the many force fields available [1] been made. Sample sizes have varied from a number of particles N 50, [2±4] to 64 N 75, [5±10] to 100 N 125, [8, 11±15] and to N 200 molecules. [16] In a few recent cases, larger samples with N % 10 3 [17,18] particles have been simulated but without really studying the full temperature dependence and identifying transitions.At atomistic resolution, the observation time window in molecular dynamics (MD) calculations has also been quite short, ranging from less than % 600 ps [2, 3, 5±7, 10, 11, 14±18] to 1 or 2 ns. [4,9,13,15,16] Recently, a few simulations lasting up to 8 and 12 ns have appeared, [8,12] but these have involved the study of one, or very few, state points: again not sufficient to assess the ability of the methodology to predict transitions. The rather short runs are probably also connected to the contradictory preliminary findings on size dependence: thus in a recent study comparing N 118 and N 994 simulations, no size dependence was found: [18] in contrast to what was found on going from N 125 to 1000. [17] These strong limitations have been paralleled by the development of molecular-level models, where molecules are considered as simple objects, either just hard or endowed with attraction and repulsion, as in the Gay ± Berne models.[19] These approximate models have proven extremely useful in studying the general properties of liquid crystals (LC), such as phase transitions and correlations, and in discussing the existence of new and yet undiscovered phases such as the biaxial [20] and the ferroelectric nematic, [21] suggesting design hints to the synthetic chemist.However, there is a class of problems and observations that are very important for the understanding of anisotropic fluids, and completely depends on an atomistic level description. The foremost example is probably the prediction of the nematic ± isotropic (NI) transition temperature T NI , a crucial element in the design of viable LC display materials that have to exist and operate in a certain temperature range, that is now tackled empirically. [22,23...

show abstract

Prediction of the Clearing Temperatures of a Series of Liquid Crystals from Molecular Structure

Cited by 36 publications

References 37 publications

Nematic Liquid Crystals for Active Matrix Displays: Molecular Design and Synthesis

Nematic Liquid Crystals for Active Matrix Displays: Molecular Design and Synthesis

Nematische Flüssigkristalle für Aktiv-Matrix-Displays: Design und Synthese

Can Nematic Transitions Be Predicted By Atomistic Simulations? A Computational Study of The Odd–Even Effect

Contact Info

Product

Resources

About