A Practical Guide to the Preparation of Liquid Crystal-Templated Microparticles

We provide a practical guide to methods and protocols that use polymer networks templated from droplets of liquid crystal (LC) to synthesize micrometer-sized polymeric particles that are chemically patchy, are anisometric in shape, possess anisotropic optical properties, and/or are mesoporous. We describe a range of methods that permit the preparation of LC droplets (containing reactive monomers) as templates for polymerization, including formation of LC-in-water emulsions by mechanical methods (e.g., vortexing), encapsulation in polymeric shells, or microfluidics. The relative merits of the methods, including ease of use and potential pitfalls, and the resulting droplet size distributions, are described. We also report a menu of approaches that can be used to control the internal configurations of the LC droplets, including changes in composition of the continuous solvent phases (e.g., addition of glycerol) and adsorption of surfactants or colloids at the interfaces of the LC droplets. Photopolymerization of the LC droplets in bipolar, radial, axial, or preradial configurations and subsequent extraction of the nonreactive mesogens generates polymeric particles that have spindle, spherical, spherocylindrical, or tear shapes, respectively. Finally, we describe how to characterize these polymeric particles, including their shape, internal structure, optical properties, and porosity. The methods described in this paper, which provide access to complex microparticles with properties relevant to separation processes, drug delivery, and optical devices, are general and versatile and can be readily developed further (e.g., by changing the choice of LC) to create an even greater diversity of microparticles.