Ring closure of carbon nanotubes

Lightly etched single-waited carbon nanotubes are chemically reacted to for m rings. The rings appear to be fully closed as opposed to open coils, as r ing-opening reactions did not change the structure of the observed rings. T he average diameter of the rings was 540 nanometers with a narrow size dist ribution. The nanotubes in solution were modeled as wormlike polymer chains , yielding a persistence length of 800 nanometers. Nanotubes shorter than t his length behave stiffly and stay nearly straight in solution. However, na notubes longer than the Kuhn segment length of 1600 nanometers undergo cons iderable thermal fluctuation, suggesting a greater flexibility of these mat erials than is generally assumed.