Liquid crystal phase diagrams: A study of seven thermotropic materials

Keyes, P. H.; Weston, H.T.; Lin, W.J.; Daniels, W. B.

doi:10.1063/1.431199

Cited by 43 publications

(6 citation statements)

References 12 publications

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“…From the value of u =(a/cr) =0.9 at T" the density of MBBA, 1.049 g/cm (at 22'C) [13], and its molecular weight, 274, one estimates that o=0.84x10 cm. By combining the constants, one obtains dT, /dp=7 K/kbar, which is on the same order as the experimental value of 20-40 K/kbar [14][15][16], but noticeably smaller. Since the value of dT, /dp depends on cr, the discrepancy between theory and experiment may indicate a strong short-range order so that the unit participating in the transition actually constitutes 3-6 molecules.…”

supporting

confidence: 69%

Nematic-isotropic phase transition: An extended mean field theory

1993

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The small magnitude of (T, -T )/T"where T, is the nematic-isotropic phase transition temperature and T denotes the virtual transition temperature, has been a long-standing puzzle in the physics of liquid crystals. We show that by extending the mean field theory to include the isotropic, densitydependent component of the molecular interaction the magnitudes of both (T, -T*)/T, and the density change at the transition automatically become in accord with the experimental values. In addition, the theory yields a value of dT, /dp, where p denotes pressure, that is on the same order as the experiment. [4], but the incorporation of that extra part also materially affects the character of the N-I transition.In particular, the predicted magnitude of (T, -T*)/T, is lowered to the experimental range, while at the same time the theory also yields the right magnitudes both for the density variation across the N-I transition as well as for the variation of T, with pressure.

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confidence: 69%

Nematic-isotropic phase transition: An extended mean field theory

1993

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“…Nematic ordering is generally counteracted by orientational fluctuations. In molecular liquid crystals, these fluctuations are due to thermal rotational diffusion, which becomes large enough to disrupt the ordered phase around ∼50-250°C, depending on pressure, concentration, and chemical composition of the liquid crystal molecules and solvent fluid (50)(51)(52). In suspensions of motile bacteria, cellular alignment and collective motion (53)(54)(55)(56) are suppressed by orientational fluctuations due to variations in flagellar motor activity and cell-cell collisions that reorient cells with respect to one another (57).…”

Section: Resultsmentioning

confidence: 99%

Architectural transitions in Vibrio cholerae biofilms at single-cell resolution

Drescher

Dunkel

Nadell

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

194

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Many bacterial species colonize surfaces and form dense 3D structures, known as biofilms, which are highly tolerant to antibiotics and constitute one of the major forms of bacterial biomass on Earth. Bacterial biofilms display remarkable changes during their development from initial attachment to maturity, yet the cellular architecture that gives rise to collective biofilm morphology during growth is largely unknown. Here, we use high-resolution optical microscopy to image all individual cells in Vibrio cholerae biofilms at different stages of development, including colonies that range in size from 2 to 4,500 cells. From these data, we extracted the precise 3D cellular arrangements, cell shapes, sizes, and global morphological features during biofilm growth on submerged glass substrates under flow. We discovered several critical transitions of the internal and external biofilm architectures that separate the major phases of V. cholerae biofilm growth. Optical imaging of biofilms with single-cell resolution provides a new window into biofilm formation that will prove invaluable to understanding the mechanics underlying biofilm development.biofilm | community | self-organization | emergent order | nematic order

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“…Generalement la distance inter-plan est de 1'ordre de la longueur d'une molecule mais pour certains composes contenant un groupe cyano (2013C=N) dans le prolongement de 1'axe moleculaire, la distance inter-plan est d'environ le double de la longueur d'une molecule d'ou le nom smectiques A bicouches. C'est le cas des produits : " Le diagramme de phase du CBOOA decrit par Lin et al [3] et Keyes et al [4] montre un point triple correspondant a la disparition de la phase smectique A et une pente negative dans la zone de surfusion de la phase smectique A. Pour voir si ce phenomene etait general il nous a paru interessant de (*) Associe au C.N.R.S. e) Produits provenant de la firme BDH.…”

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“…Ce domaine est limite par deux discontinuites ou dPjdT est infini ou nul. Ce phenomene semble etre caracteristique des smectiques A bicouches a transition smectique A-nematique quasi second ordre, car cet exemple ne se retrouve pas pour les smectiques A monocouches [4,11,12]. 11 serait interessant d'examiner ces phenomenes structuraux par rayons X ou neutrons sous pression, car la méthode d'observation optique des textures peut entrainer des ambiguites dans l'identification des mesophases.…”

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