Carbon Nanotube Gel

Carbon nanotube gel, a liquid crystalline material consisting of single-walled nanotubes, has been made by physicists at the University of Pennsylvania. Basically the gel is a mass of half-micron long nanotubes, aligned like little logs along a single direction, in a polymer matrix. The gel exhibits hallmark properties of a nematic liquid crystal (in which rod shaped molecules are aligned) including optical anisotropy (birefringence) and topological defects.

The gel's anisotropic characteristics and its sensitivity to changes in solvent quality might make it a candidate for novel applications. It could be useful, for example, as an osmotic or an electrical actuator in which changes in electrical field or salt concentration produce volume and shape changes.

The gel was made by coating the nanotubes with surfactant chemicals and mixing in polymers which form a cross-linking network among the tubes. Next the volume was compressed. The resultant densities of isolated single-wall nanotubes are higher than can be produced in simple aqueous suspensions. (Islam et al., Physical Review Letters, upcoming article; contact Arjun G. Yodh, yodh@physics.upenn.edu, 215-898-6354, Mohammad Islam, islam@physics.upenn.edu, or Tom Lubensky, tom@physics.upenn.edu.)