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.

Rheology and structure of aqueous nanocrystalline cellulose suspensions

“…The deviation may be attributed to that, under certain combination of aspect ratio and surface potential, an increasing ionic strength leads to the formation of another liquid crystalline phase at high ionic strengths. Similar results have been reported by a theoretical work by Drwenski et al [97], which was discussed in section 2.2.2 and illustrated in figure 2.8. Temperature can also affect the liquid crystallinity of NCC aqueous suspension.…”

“…where b is the ration between Deff and D. SLO method provides reasonable agreement with experimentally-observed isotropic-nematic transition for polyelectrolytes with variation in ionic strength [95], and has been used to characterise liquid crystalline behaviour of charged rigid rods including NCC [96]. Based on the SLO theory, Drwenski et al [97] recently built a isotropic-anisotropic phase map reproduced as figure 2.8 for charged rods as function of concentration, ionic strength and surface charge density. This showed two nematic phases located at low and high ionic strength respectively (as previously reported qualitatively [98,99]).…”

“…Although a few works [70,195,199], have been done on examining rheology as NCC concentration is increased to transition from isotropic, to liquid crystalline and then to jammed solid states, to the best of our knowledge, there is so far no study on the connection between liquid-solid transitions (especially phase separation or gelation process) and isotropic-anisotropic transitions. From computational works based on the modified Onsager's theory [97], Therefore, from this literature review, we conclude that classic theories in colloidal science and liquid crystalline (as discussed in section 2.2) have not been appropriately referred to in rationalising rheological observation, or that have not been sufficiently used to characterise and predict the phase transitions and behaviours of NCC aqueous suspensions.…”

Theoretical Platform for Liquid-Crystalline Self-Assembly of Collagen-Based Biomaterials

“…Second term is related to biaxial contribution and has the dependence on both polar and azimuthal angles. The intermolecular interaction and angle between rods interchangeably affect each other because the electrostatic repulsion and twisting favors perpendicular orientation while the van der Waals attraction prefers the parallel alignment (i.e., nematic phase) [49,50,54]. Hence, based on our previous work [20] and [51], we suggest the net interchain potential expressed by…”

“…Since we focus on rod-like rigid mesogen, the second virial approximation is capable of accurately describing the excluded volume effect, given by Odijk [49] and Drwenski et al [50]:…”