The surface fractal investigation on carbon nanotubes modified by the adsorption of poly(acrylic acid)

In this paper, surface fractal analysis is carried out to study the surface of carbon nanotubes after the adsorption of poly(acrylic acid) (PAA) using the thermodynamic method. The fractal dimension (dSF ) of a fractal surface, BET surface area (SBET) and pore size distribution (PSD) are calculated from low-temperature nitrogen adsorption isotherms. The value of dSF declines as the adsorption amount of PAA increases, which means the adsorption may lower the surface roughness of the carbon nanotubes. The PSD pattern was modified obviously after the adsorption of PAA because of the pore-blocking effect. Additionally, an excellent linear decrease in the BET surface area of carbon nanotubes is found as the adsorption amount of PAA increases, which can be attributed to both the pore-blocking effect and the surface-screening effect. The results of the present work may facilitate our understanding of the interaction between polymer and the carbon nanotubes at the microscale occurring on irregular interfaces.