Phase diagrams of charged colloidal rods: can a uniaxial charge distribution break chiral symmetry?

Abstract

We construct phase diagrams for charged rodlike colloids within the second-virial approximation as a function of rod concentration, salt concentration, and colloidal charge. Besides the expected isotropic-nematic transition, we also find parameter regimes with a coexistence between a nematic and a second, more highly aligned nematic phase including an isotropic-nematic-nematic triple point and a nematic-nematic critical point, which can all be explained in terms of the twisting effect. We compute the Frank elastic constants to see if the twist elastic constant can become negative, which would indicate the possibility of a cholesteric phase spontaneously forming. Although the twisting effect reduces the twist elastic constant, we find that it always remains positive. In addition, we find that for finite aspect-ratio rods the twist elastic constant is also always positive, such that there is no evidence of chiral symmetry breaking due to a uniaxial charge distribution.

Added a reference to Sec. 4 and extended discussions in Secs. 4 and 7, results unchanged

References in corpus (4)

• Cholesterics of colloidal helices: Predicting the macroscopic pitch from the particle shape and thermodynamic state
• Density Functional Theory for Chiral Nematic Liquid Crystals
• Effective shape and phase behaviour of short charged rods
• Chiral assembly of weakly curled hard rods: effect of steric chirality and polarity

Cited by in corpus (3)

• Shear induced tuning and memory effects in colloidal gels of rods and spheres
• Anisotropic electrostatic screening of charged colloids in nematic solvents
• Topological-defect-induced surface charge heterogeneities in nematic electrolytes