Materials Science

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

Authors

Abstract

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.

Content

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Supplementary material

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Supplementary Information (pdf)
Document containing: FigS1: Chemical structure of molecules; FigS2: Effect of UV light exposure on shrinkage of droplets upon heating FigS3: Optical microscopy on microparticle shrinking and swelling after photopolymerization FigS4: Schematic of microfluidic channel FigS5: Infrared analysis of 5CB, 5CB/RM257 at various processing stages FigS6: Images of fused polymer microparticles