(338z) Novel Single-Step Synthesis Technique for Shape and Size Controlled Poly(divinylbenzene) Particles Using Initiated Chemical Vapor Deposition in Nematic Liquid Crystals

The ability to synthesize shaped polymer particles will benefit a wide range of applications including targeted drug delivery and metamaterials with reconfigurable structures, but existing synthesis approaches are commonly multistep and limited to a narrow size/shape range. We have recently developed a novel single-step technology to create polymer nanoparticles and non-spherical micro particles including hemispherical micro-domes, orientation-controlled microgels, microspheres, spheroids, and disks. Divinylbenzene (DVB) was polymerized via initiated chemical vapor deposition (iCVD) in an anisotropic reaction medium such as nematic liquid crystals (LC). To avoid disruption of the LC structure, a critical limitation of past LC-templated polymerization, we leveraged LC as an intrinsic in-situ display for the tuning of the synthesis conditions and iCVD technology to precisely deliver vapor-phase reactants continuously throughout the polymerization reaction. This was accomplished by installing a custom assembly of in-situ long-focal range microscope over our reactors. Real-time monitoring, detailed image analysis and characterization of chemical composition for the particle shape progression in the polymerization process revealed key mechanistic insights of the pathway leading to formation of shaped particles. Polymerization in bulk LC led to the formation of pDVB nanoparticles, which precipitates at the LC-substrate interface to further generate secondary shaped microparticles. The nanoparticles first aggregated into oriented microgel clusters, directed by three different LC molecular alignments at the interface. On further polymerization, these microgel clusters give rise to microparticle shapes such as microspheres, spheroids, and disks. Owing to the role nanoparticle size plays in drug delivery, we have further devised strategies to tune size distributions of the nanoparticles synthesized using this innovative technique.