Functionalization and dispersion of multiwalled carbon nanotubes modified with poly- l -lysine

Poly-l-lysine (PLL) was synthesized using lysine as raw material by N-carboxyanhydride polymerization and characterized by Fourier transform infrared spectroscopy and 1H NMR. Multiwalled carbon nanotubes (MWCNTs) were non-covalently functionalized using PLL in order to prepare MWCNTs-PLL composite. MWCNTs-PLL was characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis and UV-Vis absorption spectroscopy. The dispersion of MWCNTs-PLL composite was investigated by UV-Vis absorption spectroscopy, dynamic light scattering analysis and digital photograph. The results showed that the dispersion of MWCNTs-PLL composite was obviously better than that of MWCNTs-SDS composite in water while it was also approximate with that of MWCNTs-SDBS. In addition, MWCNTs-PLL was pH-responsive in water so that it could be used as bio-nanomaterial in future.