News Release on Liquid crystals Research: February -2019

Flexible free-standing films morphology characterization: PVA/silica polymer network dispersed cholesteric liquid crystals films by sol-gel method

A novel versatile free-standing films of polyvinyl alcohol (PVA)/silica compound network distributed cholesteric liquid crystals (CLC) are ready by the sol-gel method. within the reaction of Si alkoxides tetraethoxysilane (TEOS) processes, the silicon dioxide having -OH with the -OH teams on polyvinyl resin fashioned polymer networks with Si-O-C bonds by dehydration. The cholesteric liquid crystals were incorporated into the networks. The free-standing films were obtained by the spin-coating methodology. so as to boost the compatibility and microstructure of the cholesteric liquid crystals with PVA/silica compound networks, the amphiphilic compound of hexadecyl trimethyl ammonium ion bromide (HDTMA) was introduced into the forming film solutions. Effects of the various ratios of raw materials on the structure of films were investigated. The microscopic morphology of free-standing films and therefore the uniform dispersion of CLCs within the films are characterised by polarizing optical research (POM), the sphere emission scanning microscope (FESEM), Fourier rework infrared (FT-IR) mass spectrometer and atomic force magnifier (AFM). The free-standing films exhibiting glorious CLC droplets dispersion, mechanical stability, and sensible flexibility may be helpful for versatile displays, switchable optical parts and good windows. [1]

Impact of co-doping concentration in copolymer network liquid crystals

The impact of variable the co-doping concentration of a mesogenic and a non-mesogenic chemical compound within the reactive mixtures wont to produce a polymer network LCs was investigated. Use of polymer has been found to enhance the response properties within the obtained liquid composites. The compound network within the studied polymer network LCs was examined by scanning microscopy and also the response times in varied samples were investigated. Samples were ready with varied reactive mixtures, every of that had a relentless concentration of mesogenic chemical compound, varied concentrations of non-mesogenic chemical compound, and also the same quantity of photoinitiator. These reactive mixtures were stuffed in home assembled take a look at cells with planate alignment so exposed to UV light. With increasing concentration of the non-mesogenic chemical compound, the response properties of the ensuing polymer network LC were improved. Usually, if the compound content in a very polymer network LC is raised, the edge voltage is additionally raised. However, each threshold voltages and response times were down and also the response properties were so improved within the studied polymer network LCs. This surprising behavior might be copied back to inducement a coarse compound morphology of the polymer network by employing a non-mesogenic chemical compound. [2]

Alignment of liquid crystals using Langmuir‒Blodgett films of unsymmetrical bent-core liquid crystals

The properties of the skinny films of liquid (LC) molecules will be ruled simply by external fields. The eolotropic structure of the LC molecules includes a massive impact on the electrical and optical properties of the film. The chemist monolayer (LM) of LC molecules at the air–water interface is understood to exhibit a spread of surface phases which might be transferred onto a solid substrate victimisation the Langmuir‒Blodgett (LB) technique. Here, we’ve got studied the lumen and pound films of unsymmetrically substituted bent-core LC molecules. The morphology of pound film of the molecules is found to be a dominant parameter for positioning bulk LC within the nematic section. it absolutely was found that the pound films of the bent-core molecules possessing defects favour the flattened orientation of nematic LC, whereas the pound films with fewer defects show homeotropic alignment. The defect in pound films may introduce splay or bend distortions within the nematic close to the alignment layer which might govern the flattened alignment of the majority LC. The uniform layer of pound film facilitates the molecules of nematic to anchor vertically because of a powerful van der Waals interaction between the open-chain chains resulting in a homeotropic alignment. [3]

Liquid crystals and the origin of life

The show screens of recent televisions, cell phones and laptop monitors depend on liquid crystals — materials that flow like liquids however have molecules orientating in crystal-like structures. However, liquid crystals might have contend a way more ancient role: serving to to assemble Earth’s 1st biomolecules. Researchers news in ACS Nano have found that short RNA molecules will type liquid crystals that encourage growth into longer chains. [4]

HETERO NUCLEAR DIPOLAR DECOUPLING IN THE NMR SPECTROSCOPY OF SOLIDS AND LIQUID CRYSTALS USING A SHORTER SWf-TPPM SEQUENCE WITH PHASE INCREMENTAL ALTERATION AND SUPERCYCLING

SWf-TPPM primarily based decoupling sequences are often applied to get rid of heteronuclear spin interactions in liquid crystals and solids. Here we have a tendency to gift a decoupling theme for heteronuclear couple decoupling in aeolotropic systems developed by reducing the quantity of pulse pairs within the parent SWf-TPPM. The tangential sweep of pulse durations is maintained within the sequence with a section progressive alteration followed by supercycling. The ensuing decoupling theme known as PHINTAPT (Decoupling sequences with point INcrements and TAngential variation in Pulse Times) was compared with 2 normally used decoupling sequences in solids and liquid-crystals particularly, SPINAL-64 and SWf-TPPM by analyzing the intensities of assorted resonances within the nucleon decoupled 13C spectrum of U-13C-labelled amino acid and therefore the liquid 4-n-pentyl-4’-cyanobiphenyl (5CB). The effectiveness of the decoupling theme with reference to the experimental parameters like RF intensity level, MAS frequency and nucleon offset frequency is additionally studied. [5]

Reference

[1] Niu X, Liu J, Liu W, Zhu S. Flexible free-standing films morphology characterization: PVA/silica polymer network dispersed cholesteric liquid crystals films by sol-gel method. Liquid Crystals. 2019 Jan 26:1-7. (web link)

[2] Jahanbakhsh F, Lorenz A. Impact of co-doping concentration in copolymer network liquid crystals. Liquid Crystals. 2019 Feb 6:1-9. (web link)

[3] Choudhary K, Gupta RK, Pratibha R, Sadashiva BK, Manjuladevi V. Alignment of liquid crystals using Langmuir‒Blodgett films of unsymmetrical bent-core liquid crystals. Liquid Crystals. 2019 Feb 7. (web link)

[4] Liquid crystals and the origin of life

Date: October 3, 2018

Source: American Chemical Society (web link)

[5] HETERO NUCLEAR DIPOLAR DECOUPLING IN THE NMR SPECTROSCOPY OF SOLIDS AND LIQUID CRYSTALS USING A SHORTER SWf-TPPM SEQUENCE WITH PHASE INCREMENTAL ALTERATION AND SUPERCYCLING

CYRIL AUGUSTINE

Department of Chemistry, St. Berchmans College Campus, Mahatma Gandhi University, Kottayam, Kerala, 686101, India. (web link)

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