Anomalously large bend elastic constant and faster electro-optic response in anisotropic gels formed by a dipeptide

Bhargavi, R.; Nair, Geetha G.; Prasad, S. Krishna; Prabhu, Rashmi; Yelamaggad, C. V.

doi:10.1063/1.3553413

Cited by 23 publications

(10 citation statements)

References 36 publications

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“…It may be recalled here that a factor of 5 increases in the splay elastic constant, and twoorders of magnitude enhancement in the bend elastic constant has been seen in a nematic conned in a gel matrix. 33 Increase of a similar magnitude has also been reported 34 in a ferroelectric liquid crystal conned in a polymer network. These results suggest that the interactions of the LC molecules with the walls of the polymer network perhaps increases the effective elastic constant.…”

Section: Comparison Of the Experimental Data With The Model Predictionssupporting

confidence: 74%

Influence of polymer stabilization on the dielectric relaxations of an antiferroelectric liquid crystal

2014

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Dielectric spectroscopic investigations are reported on an antiferroelectric liquid crystal in its pristine form and when stabilized by a polymer network without and with application of a DC bias field. While the inphase mode associated with the helix distortion is hardly affected, the high frequency mode connected with the antiphase fluctuations shows a large decrease with increasing concentration of the photoactive monomer used to generate the polymer stabilization. With the help of X-ray data, we rule out any interlayer nanophase segregation of the polymer strands, and argue that this strong effect is due to the large elastic interaction between the liquid crystal molecules and the polymer strands. Employing expression from a Landau theory we extract several relevant parameters, including the viscosities associated with the different relaxation modes, the elastic constant, and importantly the antiferroelectric interaction, which exhibits a substantial decrease upon polymer stabilization.

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Section: Comparison Of the Experimental Data With The Model Predictionssupporting

confidence: 74%

Influence of polymer stabilization on the dielectric relaxations of an antiferroelectric liquid crystal

2014

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“…It may be recalled that a similar increase in the Frank elastic constant was seen for a nematic in a gel environment. 4 It is possible that the gain in the elastic constant is a standard feature achieved in liquid crystals upon gelation.…”

Section: Dielectric Relaxation Spectroscopy (Drs)mentioning

confidence: 99%

“…Although, as far as connement of LC in a network is concerned, these systems resemble a polymer dispersed LC material, the thermal reversibility of the LC gel is an advantage. The mesophase involved in the investigations on LC organogels has mostly been the nematic, [1][2][3][4] but a few substances with the chiral smectic C (SmC*) phase have also been studied. Kato et al 5a reported the gelating transformation occurring within the smectic region yielding phase sequences of a sol-state 5b smectic to a gel-state smectic.…”

Section: Introductionmentioning

confidence: 99%

Influence of polarization-tilt coupling on the ferroelectric properties of smectic gels

et al. 2014

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We have studied composites of a ferroelectric liquid crystal mixture with a simple organic gelating agent, employing structural, thermal, electrical and mechanical probes, investigating the influence of the coupling between the polarization and the tilt angle on the ferroelectric properties of smectic gels. The calorimetric data, presenting clear signatures of the gelation occurring in the smectic A (SmA) phase or the isotropic phase, depending on the concentration of the gelator, help in constructing a rich diagram in the temperature-gelator concentration phase space. The atomic force microscopy imaging brings out the interesting feature of the transfer of chirality from the ferroelectric liquid crystal (FLC) to the gel strands, as exemplified by the creation of nanorope structures which have attracted much attention in recent times. The influence of gelation on the magnitude of the tilt angle appears to be dependent on the probe employed: there is no change in the values obtained by X-ray diffraction, which looks at the projection of the entire molecular length onto the layer normal. In contrast, the value from the electro-optic method, wherein the molecular-core is responsible for the results, diminishes with gelator concentration. The latter feature is copied by the magnitude of the polarization also. Dielectric spectroscopy shows that gelation weakly influences the soft mode in the SmA phase. However, the Goldstone mode behaviour is strongly dependent on the gelator concentration, with the appearance of two modes in the smectic C* (SmC*) phase of higher gel concentrations. With information obtained upon application of DC bias, the origin of the two relaxations is discussed. These data are analyzed in terms of the predictions of the Landau model proposed for the ordinary (non-gel) SmA-SmC* transition showing that the gel network enhances the linear polarization-tilt coupling over the biquadratic one. Upon gelation the system becomes mechanically strong with a large increase in the elastic moduli.

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“…Moreover, the interactions between the liquid crystals and the fibrous aggregates properly weaken an alignment force to the LC molecules conveyed from the rubbed-polyimide surfaces, which leads to the faster response [ 36 ]. Another gelator which is a monodisperse homomeric dipeptide also improves the dynamic characteristics of the electro-optical switching of the device employing these gels (compound 5 in Figure 3 ) [ 43 , 44 ]. These effects suggest not just the improvement of response speed, but also two possibilities for new applications of liquid crystals: light scattering displays and memory.…”

Section: New Functional Lc Modulated With Peptidementioning

confidence: 99%

Applications of Biomaterials to Liquid Crystals

et al. 2013

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Nowadays, chemically synthesized proteins and peptides are attractive building blocks and have potential in many important applications as biomaterials. In this review, applications of biomaterials to thermotropic liquid crystals are discussed. The review covers the improvement of the performance of liquid crystal displays using liquid crystal physical gels consisting of a liquid crystal and amino acid-based gelators, and also new functionalization of liquid crystals. Moreover, the influence of DNA, which is one of the more attractive biomaterials, dispersed in thermotropic liquid crystals and its potential use in the liquid crystal industry is described. In addition, we found interesting results during electrooptical measurements of liquid crystals doped with DNA, and explain them from the point of view of biological applications. These recent approaches suggest that these biomaterials may be applicable in the electronic device industry and should be considered as an interesting material with their physical properties having the potential to create or refine an industrial product.

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Anomalously large bend elastic constant and faster electro-optic response in anisotropic gels formed by a dipeptide

Abstract: Rheological and morphological properties of reactively compatibilized thermoplastic olefin (TPO) blendsa) J. Rheol. 56, 625 (2012); 10.1122/1.3700966Transversely tapered hybrid electro-optic polymer/sol-gel Mach-Zehnder waveguide modulators

Cited by 23 publications

References 36 publications

Influence of polymer stabilization on the dielectric relaxations of an antiferroelectric liquid crystal

Influence of polymer stabilization on the dielectric relaxations of an antiferroelectric liquid crystal

Influence of polarization-tilt coupling on the ferroelectric properties of smectic gels

Applications of Biomaterials to Liquid Crystals

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