Self-assembling, macroscopically oriented, polymer filaments; a doubly nematic organogel

Helen F. Gleeson, Sarabjot Kaur, Shajeth Srigengan, Verena Gortz, Richard Mandle, John Lydon, Harry Liu

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Nanoscale phase separation and self-organisation in liquid crystals leads to the formation of remarkable hierarchical
structures. There are several examples of heliconical nanofilament structures including in the nematic twist-bend (NTB)
phase, the B4 phase and liquid crystal gels formed from the B4 phase. Both the formation of the polymer-like structures
that permeate the soft-solids and their hierarchical structures are fascinating, not least because of the analogies that can
be drawn with naturally-occurring structures. Here, we report a remarkably simple binary system formed from a nonsymmetric
BC molecule and the rod-like liquid crystal, 5CB. The pure bent-core system exhibits both nematic and dark
conglomerate liquid crystal phases. At very low concentrations of the BC material (5-10%) this binary system
spontaneously self-assembles into a soft solid formed from nanoscale filaments that are aligned by their nematic
environment. Macroscopically, the soft solid shows behaviour that can be associated with both polymers and gels.
Interestingly, the sub-micron scale structure of the filaments appears remarkably similar to some organised fibrous
structures in nature (e.g. chitin, cellulose, insect cuticle, plant cell walls) something we attribute to self-assembly and selforganisation
in an aligned liquid crystalline environment. The nanoscale structure of the filaments show no features that
can be associated with heliconical ordering down to length scales of tens of nanometers. However, the x-ray data suggests
that a metastable rectangular columnar phase which is highly ordered in one dimension initially forms, changing to a
hexagonal lattice on a timescale of tens of minutes.
Original languageEnglish
JournalSoft Matter
Early online date29 Oct 2018
Publication statusE-pub ahead of print - 29 Oct 2018

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