In materials science, controlling the architecture of a polymer to achieve a desired property or characteristic remains an important goal.

Researchers at the California Institute of Technology, Pasadena, USA, were able to access large cyclic organic nanostructures that would be otherwise challenging to synthesize. Robert H. Grubbs and co-workers prepared ultrahigh molecular weight cyclic brush polymers from various macromonomers by employing ruthenium-based catalysts that mediate ring expansion metathesis polymerization (REMP; see scheme). These macromolecules were characterized by static LS and GPC-LS.

Meanwhile AFM techniques were used to directly image individual cyclic brush polymers, which were measured at 100–180 nm in diameter (see AFM image).

• Synthesis and Direct Imaging of Ultrahigh Molecular Weight Cyclic Brush Polymers,
  Yan Xia, Andrew J. Boydston, Robert H. Grubbs,
  Angew. Chem. 2011.
  DOI: 10.1002/ange.201101860
• Synthesis and Direct Imaging of Ultrahigh Molecular Weight Cyclic Brush Polymers,
  Yan Xia, Andrew J. Boydston, Robert H. Grubbs,
  Angew. Chem. Int. Ed. 2011.
  DOI: 10.1002/anie.201101860