Fig. 1. Self-assembly of bent-core liquid crystal. Chemical structures of (a) NOBOW and (b) hexadecane molecules; (c) the director, n, which is along the molecular long axis, and the polarization, p, which is along the bow direction; (d) smectic layers of tilted bent-core molecules. The molecules are tilted from the layer normal z, and the macroscopic polarization p, is orthogonal to both n and z; (e) the tilt directions of the top and bottom molecular arms of bent-core liquid crystals are essentially orthogonal to each other. If each molecular arm is regarded as an elastic slab, the two elastic slabs dilate along their local molecular tilt directions, which are orthogonal to each other, thus resulting in internal structural mismatch. The internal structural mismatch could be released by the formation of saddle-splay deformations; (f) bicontinuous smectic layer of the dark conglomerate (DC) phase, in which smectic layers organize into disordered focal conics; (g) helical nanofilaments of the B4 phase, in which smectic layers of finite width form uniformly twisted ribbons.

Fig. 2. Organogels formed by self-assembled 3D helical nanofilament networks of bent-core liquid crystals: (a) At 25 ℃, bent-core liquid crystal molecules self-assemble into helical nanofilament networks and the 1 wt.% NOBOW/hexadecane mixture forms organogels. At 120 ℃, NOBOW dissolves in the hexadecane solvent and the system appears as transparent fluid, showing reversible gel-sol transitions upon heating and cooling; (b) freeze-fracture transmission electron microscopy (FFTEM) image of helical nanofilament networks in the organogels; (c) transmission electron microscopy (TEM) image of individual helical nano-filaments. The inset shows the distribution of internal stress in the helical nanofilaments. The internal stress gradually increases from the helical axis towards the edges, accompanied by the color increase.

Fig. 3. Temperature sweeps of the elastic (G', solid symbols) and viscous moduli (G'', open symbols) of NOBOW/ hexadecane mixtures: (a) 0.25 wt.% NOBOW/hexadecane mixture could not form organogels and its G'' is larger than G'; (b), (c) 0.5 wt.% and 1 wt.% NOBOW/hexadecane mixtures could self-assemble into helical nanofilament networks, forming organogels. The increase rate of the elastic modulus of 0.5 wt.% NOBOW/hexadecane is 10.3 Pa/℃ and that of 1 wt.% NOBOW/hexadecane is 14.2 Pa/℃. The measurements are taken at a fixed strain of 0.5% and a fixed strain rate of 1 Hz.

Fig. 4. Strain sweeps of the elastic (G', solid symbols) and viscous moduli (G'', open symbols) of (a) 0.25 wt.%, (b) 0.5 wt.% and (c) 1 wt.% NOBOW/hexadecane mixtures measured at different temperatures of 20 ℃, 60 ℃ and 90 ℃. The mea-surements are taken at a fixed strain rate of 1 Hz.

Fig. 5. Strain rate sweeps of the elastic (G', solid symbols) and viscous moduli (G'', open symbols) of (a) 0.25 wt.%, (b) 0.5 wt.% and (c) 1 wt.% NOBOW/hexadecane mixtures measured at different temperatures of 20, 90, 100 and 120 ℃. The measurements are taken at a fixed strain of 0.5%.