Lipophilic carbon nanotubes and their phase-separation in SBS

Highly lipophilic multi-walled carbon nanotubes (MWNTs) were successfully prepared by grafting PAA onto the surface of MWNT, followed by replacing carboxyl groups of PAA with octadecylamine through amidation. The improved dispersion of functionalized MWNTs and enhanced mechanical properties of nanotube/SBS composites were observed. The composite thin films with different MWNT loading prepared via spin-coating were investigated by means of atomic force microscopy (AFM) in order to study the dispersion of MWNTs in the polymer matrix. The evolution of MWNT/SBS composite thin film surface morphology with the variation of MWNT concentration is presented. When the MWNT concentration is lower than 1 wt%, the composite thin film is homogeneous. With increase of MWNT concentration, phase separation can be clearly observed. It is found that the state of aggregation of MWNTs in the polymer matrix determine the mechanical properties of the composites.