The impact of flexibility of polyimides backbones on the stability of liquid crystal vertical alignment

RSC Advances ◽  
2016 ◽  
Vol 6 (60) ◽  
pp. 55479-55489 ◽  
Author(s):  
Xinyuan Che ◽  
Shiming Gong ◽  
Leishan Shao ◽  
Tian Lan ◽  
Fei Wang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
The Other ◽  
Side Chain ◽  
Vertical Alignment ◽  
The Stability ◽  
The Impact ◽  
Chain Type

Two side-chain-type polyimides (RPI and SPI) containing different backbones induced vertical alignments of liquid crystals, after rubbing, one maintained stable vertical, while the other transformed from vertical into parallel.

scholarly journals The impact of molecular symmetry and shape on the stability of discotic liquid crystals

2018 ◽  
Vol 96 (2) ◽  
pp. 132-138 ◽  
Author(s):  
Emilie Voisin ◽  
Vance E. Williams
Keyword(s):  
Liquid Crystals ◽  
Chain Structure ◽  
Side Chain ◽  
Discotic Liquid Crystals ◽  
Substitution Pattern ◽  
Melting Temperatures ◽  
Phase Range ◽  
Judicious Choice ◽  
The Stability ◽  
The Impact

Three series of dibenzo[a,c]phenazines were prepared in an order to assess the impact of side chain position on the phase stability of columnar liquid crystals. Each series was composed of four isomeric compounds differing only in the disposition of hexyloxy and decyloxy chains around the central aromatic core, giving rise to electronically similar compounds with varying shapes and symmetries. The substitution pattern was found to have a moderate effect on the clearing transition of the liquid crystal but a larger impact on the melting temperatures. These observations suggest a viable strategy for controlling the phase range of liquid crystals via judicious choice of peripheral chain structure and location.

Preparation and Characterization of Novel Polyimide with Thick Ring in Side Chain for Vertical Alignment Liquid Crystals

2012 ◽  
Vol 27 (1) ◽  
pp. 8-13
Author(s):  
郭春桔 GUO Chun-ju ◽  
夏森林 XIA Sen-lin ◽  
孙振 SUN Zhen ◽  
汪映寒 WANG Ying-han
Keyword(s):  
Liquid Crystals ◽  
Side Chain ◽  
Vertical Alignment

scholarly journals Gram-scale preparation of negative-type liquid crystals with a CF2CF2-carbocycle unit via an improved short-step synthetic protocol

2018 ◽  
Vol 14 ◽  
pp. 148-154 ◽  
Author(s):  
Tatsuya Kumon ◽  
Shohei Hashishita ◽  
Takumi Kida ◽  
Shigeyuki Yamada ◽  
Takashi Ishihara ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Vertical Alignment ◽  
Display Devices ◽  
Negative Type ◽  
Scale Preparation

Herein, we demonstrate an improved short-step protocol for the synthesis of multicyclic molecules having a CF2CF2-containing cyclohexadiene or cyclohexane framework in a mesogenic structure. These molecules are promising candidates for vertical alignment (VA)-mode liquid crystal (LC) display devices owing to their large negative dielectric constant. The tetrafluorinated multicyclic molecules were successfully obtained in only five or six reaction steps without the need for special handling techniques, as is generally required for thermally unstable organometallic species, representing a reduction of three reaction steps. The improved short-step synthetic protocol was also amenable to the multigram preparation of these promising molecules, which may contribute significantly to the development of novel negative-type LC molecules containing CF2CF2 carbocycles.

Pattern Formation During the Growth of Liquid Crystal Phases

MRS Bulletin ◽  
1991 ◽  
Vol 16 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Patrick Oswald ◽  
John Bechhoefer ◽  
Francisco Melo
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Unit Vector ◽  
The Other ◽  
Two Dimensional ◽  
Smectic A ◽  
Anisotropic Plastic ◽  
Fundamental Research ◽  
Crystal Phases ◽  
Columnar Mesophases

Liquid crystals, discovered just a century ago, have wide application to electrooptic displays and thermography. Their physical properties have also made them fascinating materials for more fundamental research.The name “liquid crystals” is actually a misnomer for what are more properly termed “mesophases,” that is, phases having symmetries intermediate between ordinary solids and liquids. There are three major classes of liquid crystals: nematics, smectics, and columnar mesophases. In nematics, although there is no correlation between positions of the rodlike molecules, the molecules tend to lie parallel along a common axis, labeled by a unit vector (or director) n. Smectics are more ordered. The molecules are also rodlike and are in layers. Different subtypes of smectics (labeled, for historical reasons, smectic A, smectic B,…) have layers that are more or less organized. In the smectic A phase, the layers are fluid and can glide easily over each other. In the smectic B phase, the layers have hexagonal ordering and strong interlayer corrélations. Indeed, the smectic B phase is more a highly anisotropic plastic crystal than it is a liquid crystal. Finally, columnar mesophases are obtained with disklike molecules. These molecules can stack up in columns which are themselves organized in a two-dimensional array. There is no positional correlation between molecules in one column and molecules in the other columns.

Side-chain liquid-crystal epoxy polymer binders for polymer-dispersed liquid crystals

1992 ◽  
Vol 25 (1) ◽  
pp. 133-137 ◽  
Author(s):  
Liang Chy Chien ◽  
C. Lin ◽  
David S. Fredley ◽  
James W. McCargar
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Epoxy Polymer ◽  
Side Chain ◽  
Polymer Binders ◽  
Polymer Dispersed Liquid Crystals ◽  
Polymer Dispersed

Rectilinear low-frequency shear of homogeneously aligned nematic liquid crystals

1993 ◽  
Vol 441 (1913) ◽  
pp. 559-573 ◽  
Keyword(s):  
Thin Film ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Theoretical Analysis ◽  
Low Frequency ◽  
The Other ◽  
Critical Amplitude ◽  
Linear Shear ◽  
Theoretical Results ◽  
Good Agreement

A thin film of nematic liquid crystal (ZLI 1085) is sandwiched between two horizontally mounted glass blocks, whose faces have been treated to align the molecules of the liquid parallel to the plane of the blocks. By moving one block relative to the other in its own plane, the liquid crystal is subjected to an oscillatory linear shear. Above a certain frequency-dependent amplitude, mechanical Williams domains of alternating bright and dark stripes are observed perpendicular to the direction of shear. A theoretical analysis of this phenomenon is carried out to provide predictions for both the thickness of the stripes and the critical amplitude as a function of frequency. Good agreement is found between the experimental and theoretical results.

scholarly journals Adjacent functional group effects on the assembly of columnar liquid crystals

2020 ◽  
Vol 98 (7) ◽  
pp. 379-385
Author(s):  
Carson O. Zellman ◽  
Danielle Vu ◽  
Vance E. Williams
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Self Assembly ◽  
Room Temperature ◽  
Functional Group ◽  
The Self ◽  
Clearing Temperature ◽  
Crystal Phases ◽  
Potential Strategy ◽  
The Impact

Although the impact of individual functional groups on the self-assembly of columnar liquid crystal phases has been widely studied, the effect of varying multiple substituents has received much less attention. Herein, we report a series of dibenzo[a,c]phenazines containing an alcohol or ether adjacent to an electron-withdrawing ester or acid. With one exception, these difunctional mesogens form columnar phases. The phase behavior appeared to be dominated by the electron-withdrawing substituent; transition temperatures were similar to derivatives with these groups in isolation. In most instances, the addition of an electron-donating group ortho to an ester or acid suppressed the melting temperature and elevated the clearing temperature, leading to broader liquid crystal thermal ranges. This effect was more pronounced for derivatives functionalized with longer chain hexyloxy groups. These results suggest a potential strategy for controlling the phase ranges of columnar liquid crystals and achieving room temperature mesophases.

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