Nature Chem. http://doi.org/qrv (2014)

Credit: © 2014 NPG

Polymeric microscale rings with an interior nanoscale space — or more specifically, hollow toroids — have remained a synthetic challenge for chemists. Now, Kimoon Kim and colleagues report the preparation of polymeric toroids (pictured) that retain their shape and mechanical robustness in solution. The toroids are formed from the photopolymerization of rectangular, rigid-core monomers that comprise four alkene functionalities with flexible thiol-containing crosslinkers. Using microscopic techniques, Kim and colleagues show that the structures result from the initial formation of ellipsoidal oligomeric patches that roll-up, in the longitudinal direction, to yield hollow nanotubes. These straight nanotubes bend into arc-shaped structures, and then further growth results in the formation of energetically stable, hollow microrings. The size of the microrings and the cross-sectional diameter of the hollow nanotubes can be controlled by the initial monomer and crosslinker concentrations. Cross-sectional diameters of approximately 40 nm can be achieved and this interior space can encapsulate fullerenes or ferrocene derivatives. Furthermore, the outer surface of the toroids can be decorated with silver nanoparticles.