Poly(acrylic acid)-wrapped multi-walled carbon nanotubes composite solubilization in water: definitive spectroscopic properties

A non-conjugated polymeric poly( acrylic acid) (PAA) is shown to efficiently form a stable composite with multi-walled carbon nanotubes (MWNTs). The prepared PAA-wrapped MWNTs composite is readily soluble and stable in water. The PAA-MWNTs composite exhibits interesting optical properties. FT-IR spectra show that the characteristic peaks for MWNTs are unchanged, and new chemical bonds are not formed in PAA-MWNTs, indicating that the electronic structures of the MWNTs are still intact after polymer wrapping. The obvious blue-shift of the peak at 266 nm for the C=C double bonds of pristine MWNTs upon polymer-wrapping, the systematic upshift in peak position and the enhancement in the band intensities of characteristic Raman bands of MWNTs after winding with PAA as well as the disappearance of H-1 NMR spectra for the wrapped polymer in PAA-MWNTs composite were observed, which indicate that there is strong binding of PAA to MWNTs surface via the hydropholic attraction between PAA and MWNTs. The as-prepared PAA-MWNTs dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for bioelectronic devices and biological applications where a water-based environment is needed.