Effect of Size Polydispersity on the Pitch of Nanorod Cholesterics
Laboratoire de Physique des Solides—UMR 8502, CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France
Received: 13 February 2019 / Revised: 4 March 2019 / Accepted: 4 March 2019 / Published: 10 March 2019
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Many nanoparticle-based chiral liquid crystals are composed of polydisperse rod-shaped particles with considerable spread in size or shape, affecting the mesoscale chiral properties in, as yet, unknown ways. Using an algebraic interpretation of Onsager-Straley theory for twisted nematics, we investigate the role of length polydispersity on the pitch of nanorod-based cholesterics with a continuous length polydispersity, and find that polydispersity enhances the twist elastic modulus,
, of the cholesteric material without affecting the effective helical amplitude,
. In addition, for the infinitely large average aspect ratios considered here, the dependence of the pitch on the overall rod concentration is completely unaffected by polydispersity. For a given concentration, the increase in twist elastic modulus (and reduction of the helical twist) may be up to 50% for strong size polydispersity, irrespective of the shape of the unimodal length distribution. We also demonstrate that the twist reduction is reinforced in bimodal distributions, obtained by doping a polydisperse cholesteric with very long rods. Finally, we identify a subtle, non-monotonic change of the pitch across the isotropic-cholesteric biphasic region.
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MDPI and ACS Style
Wensink, H.H. Effect of Size Polydispersity on the Pitch of Nanorod Cholesterics. Crystals 2019, 9, 143.
Wensink HH. Effect of Size Polydispersity on the Pitch of Nanorod Cholesterics. Crystals. 2019; 9(3):143.
Wensink, Henricus H. 2019. "Effect of Size Polydispersity on the Pitch of Nanorod Cholesterics." Crystals 9, no. 3: 143.
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