Processing Phase Diagram of Polymer Carbon-Nanotube Composites

The `phase diagram' of a model polymer/carbon-nanotube melt composite is measured as a function of concentration, shear stress and geometrical confinement. We observe a hierarchy of flow-induced structure, including dispersed (para) nematics, a variety of aggregates, and `jammed' fractal networks. By applying simple scaling arguments from polymer physics to rigid-rod gels, our data suggest that the portion of the network responsible for the arrest of flow is more diffuse than the full elastic network, akin to `force chains' in granular media.