scholarly journals Comment on ‘‘Photoselection in uniaxial liquid crystals: The effect of rotational Brownian motion on measurements of orientational distribution functions’’

1980 ◽  
Vol 73 (6) ◽  
pp. 3021-3021
Author(s):  
Donald B. DuPré ◽  
L. Lawrence Chapoy
Keyword(s):  
Brownian Motion ◽  
Liquid Crystals ◽  
Distribution Functions ◽  
Orientational Distribution ◽  
Rotational Brownian Motion

scholarly journals Order Parameters, Orientational Distribution Functions and Heliconical Tilt Angles of Oligomeric Liquid Crystals

2019 ◽  
Author(s):  
Richard Mandle ◽  
John W. Goodby
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Tilt Angle ◽  
Order Parameter ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Thermal Evolution ◽  
Order Parameters ◽  
Distribution Functions ◽  
Orientational Distribution

We compare the order parameters, orientational distribution functions (ODF) and heliconical tilt angles of the TB phase exhibited by a liquid-crystalline dimer (CB7CB) to a tetramer (O47) and hexamer (O67) by SAXS/WAXS. Following the N-TB phase transition we find that all order parameters decrease, and while 〈P2 〉 remains positive 〈P4 〉 becomes negative. For all three materials the order parameter 〈P6 〉 is near zero in both phases. The ODF is sugarloaf-like in the nematic phase and volcano-like in the TB phase, allowing us to estimate the heliconical tilt angle of each material and its thermal evolution. The heliconical tilt angle appears to be largely independent of the material studied despite the differing number of mesogenic units.

scholarly journals On the orientational distribution functions in de Vries-type smectic liquid crystals

2018 ◽  
Vol 45 (13-15) ◽  
pp. 2097-2108 ◽  
Author(s):  
Per Rudquist ◽  
Mikhail A. Osipov ◽  
Frank Giesselmann
Keyword(s):  
Liquid Crystals ◽  
Distribution Functions ◽  
Smectic Liquid Crystals ◽  
De Vries ◽  
Orientational Distribution

On the Behavior of an Oblate Spheroidal Hematite Particle in a Simple Shear Flow Under a Uniform Magnetic Field Applied in the Flow Direction

2013 ◽  
Author(s):  
Haruka Yokoyama ◽  
Akira Satoh
Keyword(s):  
Magnetic Field ◽  
Brownian Motion ◽  
Shear Flow ◽  
Field Strength ◽  
Flow Direction ◽  
Hematite Particle ◽  
Oblate Spheroidal ◽  
Orientational Distribution ◽  
The Magnetic Field ◽  
Rotational Brownian Motion

We discuss the orientational properties of an oblate spheroidal hematite particle and also its influence on the rheological characteristics of a dilute suspension of these magnetic particles, by means of an analytical approach based on the orientational distribution function. An oblate spheroidal hematite particle has an important characteristic that it is magnetized in a direction normal to the particle axis. This particle is assumed to conduct the rotational Brownian motion including both the usual and spin Brownian motion in a simple shear flow under a uniform magnetic field applied in the shear flow direction. In the present analysis, we have taken into account only the friction force (torque) with neglecting the hydrodynamic interactions among particles. From the balance of the torques acting on a particle, we have developed the basic equation of the orientational distribution function. This basic equation has been numerically solved in order to investigate the dependence of the orientational distribution on the magnetic field strength, shear rate and rotational Brownian motion, and also the relationship between the orientational distribution and the transport coefficients such as viscosity and diffusion coefficient. The results obtained here are summarized as follows. If both the magnetic field and the shear flow are weak, the particle does not exhibit specific directional characteristics under the influence of rotational Brownian motion. If the magnetic field is more dominant, the particle inclines such that the oblate surface is parallel to the magnetic field direction. If the Peclet number increases and the shear flow becomes more dominant, the particle shows a sharper peak of the orientational distribution in the shear flow direction. The viscosity due to the magnetic torque increases and finally converges to a constant value as the magnetic field increases. The viscosity curve has an overshoot profile and this overshoot appears at a larger value of the magnetic field strength for the case of a larger Peclet number. Moreover, the viscosity increases more significantly for a larger aspect ratio or for a more oblate hematite particle. In a sedimentation process under the gravitational field, the translational diffusion coefficient decreases with increasing magnetic field strength in the present case of the magnetic field direction.

scholarly journals Order parameters, orientational distribution functions and heliconical tilt angles of oligomeric liquid crystals

2019 ◽  
Vol 21 (13) ◽  
pp. 6839-6843 ◽  
Author(s):  
Richard J. Mandle ◽  
John W. Goodby
Keyword(s):  
Liquid Crystals ◽  
Orientational Order ◽  
Helical Structure ◽  
Order Parameters ◽  
Distribution Functions ◽  
X Ray ◽  
X Ray Scattering ◽  
Orientational Distribution ◽  
Pitch Length ◽  
Ray Scattering

Twist-bend (TB) phases possess a local helical structure with a pitch length of a few nanometers. X-ray scattering experiments on aligned samples of dimeric and oligomeric materials allows the orientational order parameters, orientational distribution functions and heliconical tilt angles to be calculated.

scholarly journals Order Parameters, Orientational Distribution Functions and Heliconical Tilt Angles of Oligomeric Liquid Crystals

2019 ◽  
Author(s):  
Richard Mandle ◽  
John W. Goodby
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Tilt Angle ◽  
Order Parameter ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Thermal Evolution ◽  
Order Parameters ◽  
Distribution Functions ◽  
Orientational Distribution

We compare the order parameters, orientational distribution functions (ODF) and heliconical tilt angles of the TB phase exhibited by a liquid-crystalline dimer (CB7CB) to a tetramer (O47) and hexamer (O67) by SAXS/WAXS. Following the N-TB phase transition we find that all order parameters decrease, and while 〈P2 〉 remains positive 〈P4 〉 becomes negative. For all three materials the order parameter 〈P6 〉 is near zero in both phases. The ODF is sugarloaf-like in the nematic phase and volcano-like in the TB phase, allowing us to estimate the heliconical tilt angle of each material and its thermal evolution. The heliconical tilt angle appears to be largely independent of the material studied despite the differing number of mesogenic units.

scholarly journals Rotational Brownian motion of an asymmetric top

1979 ◽  
Vol 19 (2) ◽  
pp. 907-919 ◽  
Author(s):  
G. W. Ford ◽  
J. T. Lewis ◽  
J. McConnell
Keyword(s):  
Brownian Motion ◽  
Asymmetric Top ◽  
Rotational Brownian Motion
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