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

Abstract

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.

Protein expression profiles of intestinal epithelial co-cultures: effect of functionalised carbon nanotube exposure

“…Colloidal stability in the culture medium, when plotted against the overall effect of the f-CNT (10 μg/mL) on protein expression [Figure 3(b)], suggests that the least stable MWCNT-COOH (which displayed the most extensive agglomeration) had the greatest effect, while the most stable SWCNT-COOH (which displayed the least agglomeration) has the least affect at this exposure. The comparative behaviour of MWCNT-COOH and MWCNT-PVP confirms our previous observations concerning their stability in aqueous dispersions (Ntim et al, 2011). …”

“…This led to the formation of carboxylic acid groups on the surface of the CNTs resulting in high aqueous dispersibility. MWCNT-PVPs were prepared according to a procedure previously reported byNtim et al (2011). Purified MWCNTs were dispersed in deionised water at a concentration of 50 mg/L with the aid of 1% sodium dodecyl sulphate (SDS).…”

Size dependent aqueous dispersibility of carboxylated multiwall carbon nanotubes

“…The HI was computed as: $$\mathrm{normalH}\mathrm{normalI}false(\%false)=\frac{A_{\mathrm{o}}-A_{\mathrm{i}}}{A_{\mathrm{normalo}}}*100$$ where A o is the UV-Visible absorbance of the c-MWCNTs before 1-octanol extraction and A i is the absorbance after extraction. 23,24 After the addition of salt however some of the CNTs were extracted into the organic layer as shown in Fig. 3(a–c).…”

“…The dispersion stability index was then determined as the UV absorbance at 24 hours relative to initial UV-Visible absorbance. 23,24 …”

Multifunctionalized Carbon Nanotubes Polymer Composites: Properties and Applications

“…However, this is not always desirable for applications in polymeric composite systems. Indeed, the surface energy of CNTs significantly different form that of the polymer matrices thus makes CNTs may not have chemical affinity to organic matrices (Song et al 2010;Ntim et al 2011). Therefore, the dispersion of CNTs into matrices becomes the biggest obstacle in practice.…”