The remarkable properties of carbon nanotubes has led to an explosion of interest in their potential to impart new functional properties to polymer materials by dispersing them at low concentrations. The properties and performance of such materials will depend critically on how processing operations such as molding or extrusion induce alignment of the nanotubes. Using the Advanced Photon Source at Argonne National Lab, researchers at Northwestern University’s MRSEC have applied powerful x-ray scattering methods to directly study flow-induced orientation in dispersions of multi-walled carbon nanotubes subjected to a well-defined shearing flow. These are the first measurements that directly quantify both the degree and direction of nanotube alignment during flow. The Northwestern team has shown that it is surprisingly difficult to generate significant nanotube alignment, a fact attributed to the propensity of the tubes to ‘entangle’ in flow due to their length.
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