Small-angle light scattering is used to assess the dispersion of poly(ethylene glycol) (PEG)-functionalized carbon nanofibers suspended in water. Analysis of these data elucidates the mechanism by which the functionalized nanofibers are solubilized in water. Linear, tube-like morphology is observed for the PEGfunctionalized nanofibers dispersed in water. However, dispersion is not down to the individual tube level as determined by analysis of the light scattering data in conjunction with transmission electron micrographs. Rather, scattering entities are polydisperse side-by-side fiber aggregates (bundles). Because of the presence of water-soluble PEG oligomers on the surfaces of the nanofibers these small-scale aggregates do not agglomerate to form the large-scale clusters that are observed for untreated and acid-treated nanofibers. Acidtreated nanofibers, by contrast, do agglomerate, but in an unusual fashion, showing a 10-h induction period of followed by linear growth of large-scale agglomerates. PEG-functionalization of the acid-treated fibers leads to stabilization by inhibiting formation of the large-scale agglomerates, not by disrupting the side-byside bundles.
