Phase behavior of the liquid crystal 8CB in a silica aerogel

Bellini, Tommaso; Clark, Noel A.; Muzny, Chris D.; Wu, Lei; Garland, C. W.; Schaefer, Dale W.; Oliver, Bernard J.

doi:10.1103/physrevlett.69.788

Cited by 223 publications

(127 citation statements)

References 20 publications

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“…This belief is supported by experiments, 27,19 and so we believe that the equilibrium results we obtain here should be directly testable in experiments. A schematic (aerogel density ρ A -temperature T ) phase diagram for a smectic liquid crystal, confined inside a low density aerogel, valid if and only if all of the bounds, Eq.1.1 are satisfied.…”

Section: N L Zmentioning

confidence: 48%

“…That such a nematic elastic glass phase may indeed exist is suggested by dynamic light scattering experiments 27,19 that show a dramatic slowing down of director fluctuation relaxations in liquid crystals in aerogel below a temperature T N EG near the bulk NI transition.…”

mentioning

confidence: 99%

“…17,18 . Our interest in this problem was stimulated by recent experiments 12,[19][20][21][22] that aim to answer these very questions. In these experiments, a liquid crystal that exhibits a bulk Nematic-Smectic-A transition is introduced into an aerogel.…”

Section: Introduction a Motivation And Backgroundmentioning

confidence: 99%

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Smectic liquid crystals in random environments

1999

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We study smectic liquid crystals in random environments, e.g., aerogel. A low temperature analysis reveals that even arbitrarily weak quenched disorder (i.e., arbitrarily low aerogel density) destroys translational (smectic) order, in agreement with recent experimental results. A harmonic approximation to the elastic energy suggests that there may be no "smectic Bragg glass" phase in this system: even at zero temperature, it is riddled with dislocation loops induced by the quenched disorder. This result would imply the destruction of orientational (nematic) order as well, and that the thermodynamically sharp NA transition is destroyed by disorder. We show, however, that the anharmonic elastic terms neglected in the above approximate treatment are important (i.e., are "relevant" in the renormalization group sense), and may, indeed, stabilize the smectic Bragg glass and the sharp phase transition into it. However, they do not alter our conclusion that translational (smectic) order is always destroyed. In contrast, we expect that weak annealed disorder should have no qualitative effects on the smectic order.

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Section: N L Zmentioning

confidence: 48%

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confidence: 99%

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Smectic liquid crystals in random environments

1999

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“…Both the collective orientational (isotropic-to-nematic) and translational (smectic) transitions have turned out to be significantly by finite size, quenched disorder and interfacial (solid-liquid) interactions introduced by the confining solid walls or the pore topology [1][2][3][4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Thermotropic nematic order upon nanocapillary filling

et al. 2013

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Optical birefringence and light absorption measurements reveal four regimes for the thermotropic behavior of a nematogen liquid (7CB) upon sequential filling of parallel-aligned capillaries of 12 nm diameter in a monolithic, mesoporous silica membrane. No molecular reorientation is observed for the first adsorbed monolayer. In the film-condensed state (up to 1 nm thickness) a weak, continuous paranematic-to-nematic (P-N) transition is found, which is shifted by 10 K below the discontinuous bulk transition at TIN =305 K. The capillary-condensed state exhibits a more pronounced, albeit still continuous P-N reordering, located 4 K below TIN. This shift vanishes abruptly on complete filling of the capillaries. It could originate in competing anchoring conditions at the free inner surfaces and at the pore walls or result from the 10 MPa tensile pressure release associated with the disappearance of concave menisci in the confined liquid upon complete filling. The study documents that the thermo-optical properties of nanoporous systems (or single nano-capillaries) can be tailored over a surprisingly wide range simply by variation of the the filling fraction with liquid crystals.

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“…Number of experiments have been dedicated to study of new features of transitions in helium [1][2][3][4][5] or liquid crystals [6][7][8][9][10] when they are confined within the pores of an aerogel. Theoretical reconstruction of those phenomena has been attempted through various models [11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Numerical study of phase transitions inside the pores of aerogels

Uzelac

Hasmy²,

Jullien³

1995

Journal of Non-Crystalline Solids

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Phase transitions inside the pores of an aerogel are investigated by modelizing the aerogel structure by diffusion-limited cluster-cluster aggregation on a cubic lattice in a finite box and considering q-states Potts variables on the empty sites interacting via nearest-neighbours. Using a finite size scaling analysing of Monte-Carlo numerical results, it is concluded that for q = 4 the transition changes from first order to second order as the aerogel concentration (density) increases. Comparison is made with the case q = 3 (where the first order transition is weaker in three dimensions) and with the case q = 4 but for randomly (non correlated) occupied sites. Possible applications to experiments are discussed.PACS numbers: 64.60-Ak, 05.50-Fh, 75.40-Mg Typeset using REVT E X * a short report of this work has been published in Phys. Rev. Lett. 74, 422 (1995).

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Phase behavior of the liquid crystal 8CB in a silica aerogel

Cited by 223 publications

References 20 publications

Smectic liquid crystals in random environments

Smectic liquid crystals in random environments

Thermotropic nematic order upon nanocapillary filling

Numerical study of phase transitions inside the pores of aerogels

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