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.