(105d) Characterizing the Inter-Particle Interactions between Length Separated Populations of Single-Wall Carbon Nanotubes Using Analytical Ultracentrifugation

For anisotropic nanoparticles such as single-wall carbon nanotubes (SWCNTs) with aspect ratios >> 10 the effects of interparticle interactions become apparent on solution behavior at very low mass fractions. In the effort that will be described, the concentration dependence of the sedimentation rate of different populations of length-separated SWCNTs was determined via analytical ultracentrifugation and used to determine the effective concentration limit for the dilute sedimentation regime and to characterize the interparticle interactions. Above the transition from the dilute sedimentation regime, on the order of 0.0001 % by particle mass fraction, sedimentation rates for the surfactant-stabilized nanotubes used in this work display significant retardation and self-sharpening not generally accounted for in published reports. The slope of the self sharpening is further utilized to determine the sign and strength of the interactions between the SWCNTs of various lengths.