Effects of polymer wrapping and covalent functionalization on the stability of MWCNT in aqueous dispersions

The colloidal behavior of aqueous dispersions of functionalized multiwall carbon nanotubes (F-CNTS) formed via carboxylation and polymer wrapping with polyvinyl pyrrolidone (PVP) is presented. The presence of polymer on the nanotube surface provided steric stabilization, and the aggregation behavior of the colloidal system was quite different from its covalently functionalized analog. Based on hydrophobicity index, particle size distribution, zeta potential as well as the aggregation kinetics studied using time-resolved dynamic light scattering, the PVP wrapped CNT was somewhat less prone to agglomeration. However, its long-term stability was lower, and this was attributed to the partial unwrapping of the polyvinyl pyrrolidone layer on the CNT surface.

(a) Particle size distribution and (b) zeta potential of the F-CNTs as a function of salt concentration. Based on hydrophobicity index, particle size distribution, zeta potential as well as the aggregation kinetics studied using time-resolved dynamic light scattering, the PVP wrapped CNT was somewhat less prone to agglomeration than the covalently functionalized MWCNT–COOH. However, its long-term stability was lower, and this was attributed to the partial unwrapping of the polyvinyl pyrrolidone layer on the CNT surface.Figure optionsDownload high-quality image (136 K)Download as PowerPoint slideResearch highlights
► Aggregation behavior of covalent functionalized and poly wrapped colloidal systems differed.
► MWCNT–PVP agglomerated less based on hydrophobicity index, particle size, zeta potential.
► MWCNT–COOH showed higher attachment efficiencies due to stronger surface charges.
► Long-term stability of MWCNT–PVP lower due to potential partial unwrapping of PVP layer.