Twist-bend nematic phases in binary mixtures of banana-shaped liquid crystalline molecules

Matsuyama, Akihiko

doi:10.1080/02678292.2017.1395483

Cited by 7 publications

(2 citation statements)

References 51 publications

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“…For completeness, we also mention that theories have been developed for bent-core liquid crystals that do not involve spontaneous polar order or a negative bend elastic constant. [13][14][15][16][17][18] Additionally, molecular field approaches [19][20][21][22][23][24][25][26][27][28][29][30] for bent-core liquid crystals exist, of which several 20,26,[28][29][30] support the idea of softening of the bend elastic constant before the onset of the polar order in bent-core liquid crystals, in agreement with Selinger et al [5][6][7] Much research in recent years has been focused on thermotropic bent-core mesogens that become liquid crystalline upon lowering the temperature. Very recently, various routes have been developed to synthesize lyotropic colloidal model systems of bentcore molecules, e.g., silica rods with a sharp kink [31][32][33] or smoothly curved SU-8 rods.…”

Section: Introductionsupporting

confidence: 65%

A Landau–de Gennes theory for twist-bend and splay-bend nematic phases of colloidal suspensions of bent rods

Anzivino

Roij

Dijkstra

2020

The Journal of Chemical Physics

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We develop a phenomenological Landau-de Gennes (LdG) theory for lyotropic colloidal suspensions of bent rods using a Q-tensor expansion of the chemical-potential dependent grand potential. In addition, we introduce a bend flexoelectric term, coupling the polarization and the divergence of the Q-tensor, to study the stability of uniaxial (N), twist-bend (N TB ), and splay-bend (N SB ) nematic phases of colloidal bent rods. We first show that a mapping can be found between the LdG theory and the Oseen-Frank theory. By breaking the degeneracy between the splay and bend elastic constants, we find that the LdG theory predicts either an N-N TB -N SB or an N-N SB -N TB phase sequence upon increasing the particle concentration. Finally, we employ our theory to study the first-order N-N TB phase transition, for which we find that K 33 as well as its renormalized version K eff 33 remain positive at the transition, whereas K eff 33 vanishes at the nematic spinodal. We connect these findings to recent simulation results.

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Section: Introductionsupporting

confidence: 65%

A Landau–de Gennes theory for twist-bend and splay-bend nematic phases of colloidal suspensions of bent rods

Anzivino

Roij

Dijkstra

2020

The Journal of Chemical Physics

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show abstract

“…Additionally, molecular field approaches [64,[139][140][141][142][143][144][145][146][147][148][149] for bent-core liquid crystals exist, of which several [139,145,[147][148][149] support the idea of a softening of the bend elastic constant before the onset of polar order in bent-core liquid crystals, in agreement with Selinger et al [52,53,134] Much research in recent years has been focused on thermotropic bent-core mesogens that become liquid crystalline upon lowering the temperature. Very recently, various routes have been developed to synthesize lyotropic colloidal model systems of bent-core molecules, e.g.…”

Section: Introductionsupporting

confidence: 68%

On the effect of capillarity and polarity in colloidal suspensions of nanoparticles

Anzivino¹

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Chapter 1 Phenomenological background 1.ColloidsThis thesis deals with a series of phenomena occurring in systems composed of particles with dimensions ranging from a few nanometers up to several microns. The structural properties of these so-called colloidal systems can easily be altered by mechanical or thermal stress of the order of thermal fluctuations. In this sense they belong to the broad branch of physics known as soft matter [1]. Examples of colloidal systems are present in tremendous numbers in every day life: suspensions/emulsions such as milk, blood, paint, liquid crystal displays in electronic equipment, gels and lotions, polymers, biological entities such as bacteria, sperm cells, tissues, etc.A very important property of colloids is that they perform a random motion, when suspended in a solvent such as water or oil. This random motion is commonly referred to as Brownian motion, since observed for the first time by R. Brown in 1827 [2] for pollen particles. The theoretical explanation of Brown's observations was provided by A. Einstein in 1905 [3] amongst others, and, a few years later, definitive evidence of Brownian motion was provided in experiments by J. Perrin [4]. Because of the Brownian motion, colloidal systems are well suited to be studied by statistical mechanics. Indeed, colloids in a solvent are able to move around in the solvent and can interact with each other or with the solvent molecules. As a consequence they are in principle able to explore all possible configurations in which the system (colloids+solvent) can be, thus satisfying the ergodic hypothesis, which is the central assumption of statistical mechanics. However, as in atomic and molecular systems, ergodicity also breaks in colloidal systems when approaching the glass transition [5,6].On the experimental side, the possibility of manipulating colloidal systems has widely increased in the last decades. Indeed, important advancements have been made in preparing colloidal suspensions and tuning their properties [7,8]. Moreover, because of their size and slow dynamics, colloids are well suited to be studied in real space and real time using advanced microscopy techniques [9].Out of the endless possibilities of colloidal systems, we will focus in this thesis on colloids trapped at a fluid-fluid interface, and on liquid crystalline colloidal systems. Chains of colloids at fluid-fluid interfacesA situation in which colloidal particles display striking features is when they are trapped at a fluid-fluid interface, i.e. at the interface of two immiscible fluids. Indeed, as firstly experimentally observed at the beginning of the twentieth century [10,11], and successively theoretically shown in a seminal paper by Pieranski [12], sub-millimiter sized particles strongly adsorb at fluid-fluid interfaces in order to reduce the interfacial area, and hence the free energy of the interface [13]. Once adsorbed, colloidal particles can give rise to stable monolayers.Recently, capillarity has been invoked to explain this intriguing phenomenon [1...

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Dielectric and viscoelastic investigations in a binary system of soft- and rigid-bent mesogens exhibiting the twist-bend nematic phase

Varshini

Rao

Hiremath

et al. 2021

Journal of Molecular Liquids

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Twist-bend nematic phases in binary mixtures of banana-shaped liquid crystalline molecules

Cited by 7 publications

References 51 publications

A Landau–de Gennes theory for twist-bend and splay-bend nematic phases of colloidal suspensions of bent rods

A Landau–de Gennes theory for twist-bend and splay-bend nematic phases of colloidal suspensions of bent rods

On the effect of capillarity and polarity in colloidal suspensions of nanoparticles

Dielectric and viscoelastic investigations in a binary system of soft- and rigid-bent mesogens exhibiting the twist-bend nematic phase

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