Polydispersity Stabilizes Biaxial Nematic Liquid Crystals

Belli, Simone; Patti, Alessandro; Dijkstra, Marjolein; Roij, René van

doi:10.1103/physrevlett.107.148303

Cited by 67 publications

(104 citation statements)

References 34 publications

(51 reference statements)

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“…1), as a function of the reservoir depletant concentration n D . In order to allow for a comparison with previous experimental [28] and theoretical [17] work on the subject, the aspect ratios are chosen as l/t = 9.3 and w/t = 3.0, while for the cubic depletant we set d/t = 1.0. At n D = 0 the 6 excluded-volume matrix elements are positive definite, but with increasing n D their value decreases until becoming negative (see E 11 in Fig.…”

Section: Resultsmentioning

confidence: 99%

Depletion-induced biaxial nematic states of boardlike particles

Belli

Dijkstra

Roij

2012

J. Phys.: Condens. Matter

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With the aim of investigating the stability conditions of biaxial nematic liquid crystals, we study the effect of adding a non-adsorbing ideal depletant on the phase behavior of colloidal hard boardlike particles. We take into account the presence of the depletant by introducing an effective depletion attraction between a pair of boardlike particles. At fixed depletant fugacity, the stable liquid crystal phase is determined through a mean-field theory with restricted orientations. Interestingly, we predict that for slightly elongated boardlike particles a critical depletant density exists, where the system undergoes a direct transition from an isotropic liquid to a biaxial nematic phase. As a consequence, by tuning the depletant density, an easy experimental control parameter, one can stabilize states of high biaxial nematic order even when these states are unstable for pure systems of boardlike particles.

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Section: Resultsmentioning

confidence: 99%

Depletion-induced biaxial nematic states of boardlike particles

Belli

Dijkstra

Roij

2012

J. Phys.: Condens. Matter

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“…At the lower osmotic pressures higher up in the sample, the biaxiality remained (although with slightly increasing correlation lengths, which is to be expected for a sedimented sample) without passing through a uniaxial nematic region before entering the isotropic phase. At first sight, this suggests that the sample is very close to passing through the bicritical point in the centre of figure 5, but it turns out that the polydispersity may play a significant role [82]. Also the smectic phasedisplaying optical Bragg reflections-below the nematic phase was clearly biaxial.…”

Section: Goethitementioning

confidence: 99%

Liquid crystal phase transitions in suspensions of mineral colloids: new life from old roots

Lekkerkerker

Vroege

2013

Phil. Trans. R. Soc. A.

127

104

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A review is given of the field of mineral colloidal liquid crystals: liquid crystal phases formed by individual mineral particles within colloidal suspensions. Starting from their discovery in the 1920s, we discuss developments on the levels of both fundamentals and applications. We conclude by highlighting some promising results from recent years, which may point the way towards future developments.

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“…Interestingly, an increasing polydispersity in shape and size favors the biaxial nematic phase over other ordered phases [27]. In addition to this, binary mixtures consisting of board-shaped particles with added polymers can stabilize biaxial order very efficiently [28].…”

Section: Introductionmentioning

confidence: 99%

“…The recent experimental observation of biaxial nematic order in suspensions of board-like goethite nanorods [23][24][25] has prompted several theoretical studies in order to determine the global phase behavior of hard board-shaped particles [5,26] and also to identify those processes which promote the formation of the biaxial nematic phase [27,28]. Interestingly, an increasing polydispersity in shape and size favors the biaxial nematic phase over other ordered phases [27].…”

Section: Introductionmentioning

confidence: 99%

Effect of shape biaxiality on the phase behavior of colloidal liquid-crystal monolayers

Gonzalez-Pinto

Martı́nez-Ratón

Velasco

et al. 2015

Phys. Chem. Chem. Phys.

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We extend our previous work on monolayers of uniaxial particles [J. Chem. Phys. 140, 204906 (2014)] to study the effect of particle biaxiality on the phase behavior of liquid-crystal monolayers.Particles are modelled as board-like hard bodies with three different edge lengths σ 1 ≥ σ 2 ≥ σ 3 , and use is made of the restricted-orientation approximation (Zwanzig model). A density-functional formalism based on the fundamental-measure theory is used to calculate phase diagrams for a wide range of values of the largest aspect ratio (κ 1 = σ 1 /σ 3 ∈ [1, 100]). We find that particle biaxiality in general destabilizes the biaxial nematic phase already present in monolayers of uniaxial particles.While plate-like particles exhibit strong biaxial ordering, rod-like ones with κ 1 > 21.34 exhibit reentrant uniaxial and biaxial phases. As particle geometry is changed from uniaxial-to increasingly biaxial-rod-like, the region of biaxiality is reduced, eventually ending in a critical-end point. For κ 1 > 60, a density gap opens up in which the biaxial nematic phase is stable for any particle biaxiality. Regions of the phase diagram where packing-fraction inversion occurs (i.e. packing fraction is a decreasing function of density) are found. Our results are compared with the recent experimental studies on nematic phases of magnetic nanorods.

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Polydispersity Stabilizes Biaxial Nematic Liquid Crystals

Cited by 67 publications

References 34 publications

Depletion-induced biaxial nematic states of boardlike particles

Depletion-induced biaxial nematic states of boardlike particles

Liquid crystal phase transitions in suspensions of mineral colloids: new life from old roots

Effect of shape biaxiality on the phase behavior of colloidal liquid-crystal monolayers

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