Synthesis of Optically Complex, Porous and Anisometric Polymeric Microparticles by Templating from Liquid Crystalline...

We demonstrate that aqueous dispersions of micrometer-sized liquid crystal (LC) droplets provide the basis of a general and facile methodology for the templated synthesis of spherical and non-spherical polymeric microparticles with complex internal structure and porosity. Specifically, we prepared nematic droplets of reactive/non-reactive mesogens with distinct internal configurations using a range of approaches, photo-polymerized the reactive mesogen 4-(3-acryloyoxypropyloxy) benzoic acid 2-methyl-1,4-phenylene ester (RM257) within the LC droplets, and then extracted the non-reactive mesogens to yield polymeric particles. We found that LC droplets exhibiting bipolar, radial, axial or preradial configurations template the formation of spindle-shaped, spherical, spherocylindrical or tear-shaped polymeric microparticles, respectively. Each type of microparticle exhibited distinct optical signatures indicating the presence of an internal LC-templated, anisotropic polymer network. In addition, by using a microfluidic system to generate monodisperse LC droplets containing 10% - 40% wt/wt of RM257, we formed spindle-shaped microparticles with tailored aspect ratios ranging from 2.4 to 1.2. We show also the mass density of spherical microparticles templated from radial LC droplets can be tuned to range from 0.2 to 0.6 g/cm³, revealing the introduction of porosity (confirmed by electron microscopy) with a volume-average pore diameter of 39 ± 16 nm (obtained from nitrogen sorption isotherms).