  The ability to synthesize shape-controlled 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. Using a novel single-step
synthesis technique, a variety of shapes including nanospheres, hemispherical
micro-domes, orientation-controlled microgels, microspheres, spheroids, and
micro-discs were obtained. The shape-controlled particles were synthesized by
polymerizing divinylbenzene (DVB) via initiated chemical vapor deposition
(iCVD) in nematic liquid crystals (LC). iCVD continuously and precisely
delivered vapor-phase reactants, thus avoiding disruption of the LC structure,
a critical limitation in past LC-templated polymerization. That shape
controllability was further enabled by leveraging LC as a real-time display of
the polymerization conditions and progression, using a custom in-situ
long-focal range microscope. Detailed image analysis unraveled key mechanisms
in polymer synthesis in LC. Poor solubilization by nematic LC led to the
formation of pDVB nanospheres, distinct from microspheres obtained in isotropic
solvents. The nanospheres precipitated to the LC-solid interface and further
aggregated into microgel clusters with controlled orientation that was guided
by the LC molecular alignment. On further polymerization, microgel clusters
phase separated to form microspheres, spheroids, and unique disc-shaped
particles.
