Statistical Theory of Elastic Constants of Cholesteric Liquid Crystals

Kapanowski, A.

doi:10.1515/zna-2002-3-401

Cited by 5 publications

(2 citation statements)

References 29 publications

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“…A more general electrostatic model potential for chiral interactions was proposed much earlier by Goossens [44] based on a spatial arrangement of dipoledipole and dipole-quadrupole interactions which can be cast as a multipole expansion in terms of tractable pseudo-scalar potentials [45]. This type of electrostatic description of the chiral interaction can be combined with a Maier-Saupe meanfield treatment [46][47][48][49][50][51], or with a bare hard-core model and treated within the seminal theory of Onsager [52][53][54].…”

Section: Introductionmentioning

confidence: 99%

Cholesteric order in systems of helical Yukawa rods

Wensink¹,

Jackson²

2011

J. Phys.: Condens. Matter

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We consider the interaction potential between two chiral rod-like colloids which consist of a thin cylindrical backbone decorated with a helical charge distribution on the cylinder surface. For sufficiently slender helical rods a simple scaling expression is derived which relates the chiral 'twisting' potential to the microscopic properties of the particles, such as the internal helical pitch, charge density and electrostatic screening parameter. To predict the behaviour of the macroscopic cholesteric pitch of the fluid bulk phase we invoke a simple second-virial theory generalized to treat anisotropic states with weakly twisted director fields. It is shown that, while particles with weakly coiled helices always form a cholesteric phase whose helical sense is commensurate with that of the internal helix, more strongly coiled rods lead to the formation of a cholesteric state of opposite sense. The correlation between the helical symmetry at the microscopic and macroscopic scale is found to be very sensitive to the pitch of the Yukawa helix. Mixing helical particles of sufficiently disparate length and internal pitch may give rise to a demixing of the uniform cholesteric phase into two fractions with a different macroscopic pitch. Our findings could be relevant to the interpretation of experimental observations in systems of cellulose and chitin microfibres, DNA and fd virus rods.

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Section: Introductionmentioning

confidence: 99%

Cholesteric order in systems of helical Yukawa rods

Wensink¹,

Jackson²

2011

J. Phys.: Condens. Matter

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“…A more general electrostatic model potential for chiral interactions was proposed much earlier by Goossens 29 based on a spatial arrangement of dipole-dipole and dipole-quadrupole interactions which can be cast into a multipole expansion in terms of tractable pseudo-scalar potentials 30 . This type of electrostatic description of the chiral interaction can be combined with a Maier-Saupe mean-field treatment (see, for example references 31,32,33,34,35,36 , or with a bare hard-core model and treated within the seminal theory of Onsager 37 (as in the recent study of chiral hard spherocylinders for systems with perfect local nematic order 38 ).…”

Section: Introductionmentioning

confidence: 99%

Generalized van der Waals theory for the twist elastic modulus and helical pitch of cholesterics

Wensink

Jackson

2009

The Journal of Chemical Physics

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We present a generalized van der Waals theory for a lyotropic cholesteric system of chiral spherocylinders based on the classical Onsager theory for hard anisometric bodies. The rods consist of a hard spherocylindrical backbone surrounded with a square-well potential to account for attractive (or soft repulsive) interactions. Long-ranged chiral interactions are described by means of a simple pseudoscalar potential which is appropriate for weak chiral forces of a predominant electrostatic origin. Based on the formalism proposed by Straley [Phys. Rev. A 14, 1835 (1976)], we derive explicit algebraic expressions for the twist elastic modulus and the cholesteric pitch for rods as a function of density and temperature. The pitch varies nonmonotonically with density, with a sharp decrease at low packing fractions and a marked increase at higher packing fractions. A similar trend is found for the temperature dependence. The unwinding of the helical pitch at high densities (or low temperatures) originates from a strong enhancement of the local nematic order and the corresponding increase in the twist elastic resistance associated with near-parallel local rod configurations. This contrasts with the commonly held view that the increase in pitch with decreasing temperature as often observed in cholesterics is due to layer formation resulting from presmectic fluctuations. The increase in pitch with increasing temperature is consistent with an entropic unwinding as the chiral interaction becomes less significant than the thermal energy. The variation of the pitch with density, temperature, and contour length is in qualitative agreement with recent experimental results on colloidal fd rods.

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A study of steric chirality: the chiral nematic phase of a system of chiral two-site HGO molecules

Varga

Jackson

2011

Molecular Physics

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Statistical Theory of Elastic Constants of Cholesteric Liquid Crystals

Cited by 5 publications

References 29 publications

Cholesteric order in systems of helical Yukawa rods

Cholesteric order in systems of helical Yukawa rods

Generalized van der Waals theory for the twist elastic modulus and helical pitch of cholesterics

A study of steric chirality: the chiral nematic phase of a system of chiral two-site HGO molecules

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