Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Significance Linear defects-disclinations in thermotropic liquid crystals are known to serve as templates for self-assembly of nanoparticles and molecules into continuous thread-like structures. Here, we show that disclinations in lyotropic cholesteric liquid crystals can act as templates for nanoparticle dispersions, producing both continuous and discontinuous morphologies, with discrete beads of the dispersion periodically organized along the disclination axis. The beading effect is rooted in the anisotropic properties of the cholesteric phase. The observed mode of assembly expands the design spectrum of architectures of soft materials. The lyotropic nature of the liquid crystal formed by an aqueous suspension of cellulose nanocrystals broadens the range of materials used for the self-assembly of periodical structures. An important goal of the modern soft matter science is to discover new self-assembly modalities to precisely control the placement of small particles in space. Spatial inhomogeneity of liquid crystals offers the capability to organize colloids in certain regions such as the cores of the topological defects. Here we report two self-assembly modes of nanoparticles in linear defects-disclinations in a lyotropic colloidal cholesteric liquid crystal: a continuous helicoidal thread and a periodic array of discrete beads. The beads form one-dimensional arrays with a periodicity that matches half a pitch of the cholesteric phase. The periodic assembly is governed by the anisotropic surface tension and elasticity at the interface of beads with the liquid crystal. This mode of self-assembly of nanoparticles in disclinations expands our ability to use topological defects in liquid crystals as templates for the organization of nanocolloids.