Influence of biosafe amino acid-functionalized multiwalled carbon nanotubes on the morphology and thermal properties of the poly(amide–imide) nanocomposites containing N,N ′-(pyromellitoyl)-bis- S -valine segments

In this study, S-valine-functionalized multiwalled carbon nanotubes (f-MWCNTs)/poly(amide–imide) (PAI) bionanocomposites (BNC)s were prepared by a simple ultrasonication-assisted solution blending process. First, carboxylated MWCNTs were functionalized with S-valine to achieve a fine dispersion of f-MWCNT bundles in the PAI matrix due to hydrogen bonding and π–π stacking interaction between f-MWCNTs and polymer functional groups and aromatic moieties. The existence of S-valine as a biodegradable segment in both f-MWCNTs and optically active PAI provided potentially biodegradable nanocomposites and caused compatibility between f-MWCNTs and the polymer matrix. The obtained BNCs were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The TEM and FESEM images confirmed good dispersion of f-MWCNTs in the polymer matrix. The results of TGA and XRD analysis suggested that a good thermal stability and dispersion occurred especially with low filler amounts (5 wt%) of f-MWCNTs.