Issue 41, 2014

Self-assembly of hard helices: a rich and unconventional polymorphism

Abstract

Hard helices can be regarded as a paradigmatic elementary model for a number of natural and synthetic soft matter systems, all featuring the helix as their basic structural unit, from natural polynucleotides and polypeptides to synthetic helical polymers, and from bacterial flagella to colloidal helices. Here we present an extensive investigation of the phase diagram of hard helices using a variety of methods. Isobaric Monte Carlo numerical simulations are used to trace the phase diagram; on going from the low-density isotropic to the high-density compact phases a rich polymorphism is observed, exhibiting a special chiral screw-like nematic phase and a number of chiral and/or polar smectic phases. We present full characterization of the latter, showing that they have unconventional features, ascribable to the helical shape of the constituent particles. Equal area construction is used to locate the isotropic-to-nematic phase transition, and the results are compared with those stemming from an Onsager-like theory. Density functional theory is also used to study the nematic-to-screw-nematic phase transition; within the simplifying assumption of perfectly parallel helices, we compare different levels of approximation, that is second- and third-virial expansions and a Parsons–Lee correction.

Graphical abstract: Self-assembly of hard helices: a rich and unconventional polymorphism

Article information

Article type
Paper
Submitted
17 Jun 2014
Accepted
31 Jul 2014
First published
01 Aug 2014

Soft Matter, 2014,10, 8171-8187

Author version available

Self-assembly of hard helices: a rich and unconventional polymorphism

H. B. Kolli, E. Frezza, G. Cinacchi, A. Ferrarini, A. Giacometti, T. S. Hudson, C. De Michele and F. Sciortino, Soft Matter, 2014, 10, 8171 DOI: 10.1039/C4SM01305K

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