Liquid Crystal-Templated Porous Microparticles via Photopolymerisation of Temperature-Induced Droplets in a Binary Liquid Mixture

Porous polymeric microspheres are an emerging class of materials, offering stimuli-responsive cargo uptake and release. Herein, we describe a new approach to fabricate porous anisotropic microspheres based on temperature-induced droplet formation and light-induced polymerisation. Anisotropic liquid crystal (LC) microparticles were prepared by exploiting the partial miscibility of a thermotropic LC mixture composed of 4-cyano-4’- pentylbiphenyl (5CB, unreactive mesogens) with 2-methyl- 1,4-phenylene bis4-[3-(acryloyloxy)propoxy] benzoate (RM257, reactive mesogens) in methanol (MeOH). Isotropic 5CB/RM257-rich droplets were generated by cooling below the binodal curve (20°C), and the isotropic-to-nematic transition occurred after cooling below 0°C. The resulting 5CB/RM257-rich droplets with radial configuration were subsequently polymerised under UV light, resulting in nematic microparticles. Upon heating the mixture, the 5CB mesogens underwent a nematic-isotropic transition and eventually became homogeneous with MeOH, while the polymerised RM257 preserved its radial configuration. Repeated cycles of cooling and heating resulted in swelling and shrinking of the porous microparticles. The use of a reversible materials templating approach to obtain porous microparticles provides new insights into binary liquid manipulation and potential for microparticle production.