Polymerizable liquid crystals consisting of reactive end groups and stiff cores are reactive mesogens. The mesogenic feature of them, as well as polymerization, have resulted in a wide range of applications. Both LCDs and OLEDs require functional films composed of reactive mesogens. They vastly improve image quality in those displays.
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The basic information of RM257
RM257 CAS NO. 174063-87-7


Product Name: 2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate)
Molecular Formula: C33H32O10

RM257 is a reactive diacrylate mesogen substance. It is a bi-functional linear polymer monomer that can also serve as an LCD monomer, RM material, and electronic chemical.

What are the applications of RM257?

The backflow effect in an LCD is depicted as optical bounce (OB) in the applying voltage, vertical alignment liquid crystal display (VA-LCD). The OB phenomenon notably enhances response time, limiting the use of VA-LCD in LC devices that require rapid response. A little amount of RM257 can be applied to VA-LCD to eliminate the OB phenomena during polymerization.

Hence, a rapid reaction rate can be achieved. A small amount of RM257 increases the saturation voltage while diminishing the bright state transmittance. The VA-LCD with polymer monomer has a straightforward production process, which is essential for its wide range of applications.

After polymerization, the polymer monomer in the VA cell creates numerous vertical alignment fibers. During the application of an electric field, it has a particular anchoring effect on the LC molecules. Furthermore, the horizontal flow of LC molecules can be obstructed. Thus, the backflow effect is eliminated.

A photo-stable azo dye photoalignment surface for liquid crystal had already been proposed and demonstrated by researchers. A thin photopolymerizable liquid crystal polymer is stacked on top of an azo dye photoalignment layer to form the alignment surface. For the azo dye alignment layer, the liquid crystal polymer works as a passivation layer. Once the liquid crystal polymer has been polymerized, the azo dye’s alignment orientation cannot be rewritten.

As a result, the synthetic alignment surface is strong, reproducible, and stable. Furthermore, measurements denote that the alignment characteristics of this synthetic alignment surface are comparable to those of regular polyimide. Here, RM257 was used for the liquid crystal polymer. The liquid crystalline monomers contain reactive acrylate end groups, which polymerize with one another in the presence of photoinitiators and ultraviolet light to form a solid network. Because of the mutual polymerization of their groups, the orientation of the liquid crystal molecules is fixed after photopolymerization. These reactive mesogens liquid crystal polymers are exceedingly unreactive, inert, and heat resistant. Hence, it is the ideal material for passivation.

The characteristics of RM257

(1) A nematic liquid crystal monomer (at 67–130 °C), that can be aligned by an electric field.
(2) The molecule has a stick structure and a length ratio of 4:1.
(3) Polar or polarizable groups are present at the molecular terminals, allowing the molecules to remain in an ordered orientation.
(4) The molecule’s long axis is both flexible and rigid.

What are the mixtures that RM257 can form?

Liquid crystalline elastomers (LCEs) are anisotropic, soft substances that undergo substantial shape alterations when subjected to diverse stimuli. LCE films can be made by mixing mesogenic diacrylates (RM82 CAS NO.125248-71-7 and RM257) with a dithiol chain-transfer agent. A nematic LC mixture comprising reactive mesogen (RM82 /RM257 in a ratio of 20/80) is used to fill liquid crystal cells. Moreover, the formulation of cholesteric layers requires this mixture.

To check the effects of the polymer network on electrically induced reflection band broadening of cholesteric liquid crystal, the mixture of RM257 and RM23 (CAS NO.83847-14-7) is utilized.

In the RM257/5CB mixtures, RM257 and 5CB (CAS NO. 40817-08-1) are reactive mesogen and orientation-inducible LC porogen, respectively. This mixture is used for the preparation of anisotropic porous liquid crystal (LC) particles with ~ 60 µm diameters.
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The related chemicals

(4-hydroxyphenyl)boronic acid CAS NO.71597-85-8
1-bromo-4-(but-3-en-1-yl)benzene CAS NO.15451-32-8
(3-fluoro-4′-pentyl-[1,1′-biphenyl]-4-yl)boronic acid CAS NO.163129-14-4
1-ethoxy-2,3-difluorobenzene CAS NO.121219-07-6
1-butoxy-2,3-difluorobenzene CAS NO.136239-66-2

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