This study introduces liquid crystal (LC) Janus droplets. We describe a process for the preparation of these droplets, which consist of nematic LC and polymer compartments. The process employs solvent-induced phase separation in emulsion droplets generated by microfluidics. The droplet morphology was systematically investigated and demonstrated to be sensitive to the surfactant concentration in the background phase, the compartment volume ratio, and the possible coalescence of multiple Janus droplets. Interestingly, the combination of a polymer and an anisotropic LC introduces new functionalities into Janus droplets, and these properties lead to unusual dynamical behaviors. The different densities and solubilities of the two compartments produce gravity-induced alignment, tumbling, and directional self-propelled motion of Janus droplets. LC Janus droplets with remarkable optical properties and dynamical behaviors thus offer new avenues for applications of Janus colloids and active soft matter.

With few exceptions, polydispersity or molecular heterogeneity in matter tends to impede selfassembly and state transformation 1-3. Here we report shape transition studies of nematic liquid crystal oligomer (NLCO) drops, which reveal, surprisingly, that molecular heterogeneity in the drops promotes reversible transitions to a rich variety of non-spherical morphologies with unique internal structure. Previously, shape transitions of homogeneous liquid drops with monodisperse ingredients have been reported in equilibrium 4-7 and non-equilibrium studies 8, 9 , with the latter producing filaments at active interfaces, albeit randomly without control. Our experiments employ equilibrium suspensions of drops composed of polydisperse NLCOs. Variation of oligomer chain length distribution, temperature, and surfactant concentration alters the balance between NLCO elastic energy and interfacial energy and drives formation of visually striking nematic structures ranging from roughened spheres to flowers to branched filamentous networks with controllable diameters. The branched structures with confined LC director fields can be produced reversibly over centimeter areas and converted into LC elastomers by UV curing. Remarkably, observations and modeling reveal that chain length polydispersity plays a crucial role in driving these morphogenic phenomena, via spatial segregation. This insight suggests new routes for encoding network structure and function in soft materials. We study NLCO drops, tens of microns in diameter, dispersed in water containing sodium dodecyl sulfate (SDS) surfactant. SDS creates a strong preference for homeotropic anchoring, wherein the nematic director (molecular orientation) is perpendicular to the drop surface (Fig. 1a). Each surfactant-stabilized NLCO emulsion drop contains a mixture of RM82 monomer and oligomers of RM82 (1,4-bis-[4-(6-Reprints and permissions information is available at www.nature.com/reprints.Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Liquid crystalline phases of matter often exhibit visually stunning patterns or textures. Mostly, these liquid crystal (LC) configurations are uniquely determined by bulk LC elasticity, surface anchoring conditions, and confinement...

We prepare two-dimensional crystalline packings of colloidal particles on surfaces of the nematic liquid crystal (NLC) 5CB, and we investigate the diffusion and vibrational phonon modes of these particles using video microscopy. Short-time particle diffusion at the air-NLC interface is well described by a Stokes-Einstein model with viscosity similar to that of 5CB. Crystal phonon modes, measured by particle displacement covariance techniques, are demonstrated to depend on the elastic constants of 5CB through interparticle forces produced by LC defects that extend from the interface into the underlying bulk material. The displacement correlations permit characterization of transverse and longitudinal sound velocities of the crystal packings, as well as the particle interactions produced by the LC defects. All behaviors are studied in the nematic phase as a function of increasing temperature up to the nematic-isotropic transition.