Functionalization of multiwalled carbon nanotubes with S-valine amino acid and its reinforcement on amino acid-containing poly(amide-imide) bionanocomposites

Abstract

Chemical functionalization of multiwalled carbon nanotubes (MWCNT)s with S-valine amino acid was discussed to give enhanced solubility and dispersibility by rapidly and efficiently generating an appreciable amount of hydrophilic functional groups using microwave radiation. Surface functionality groups and the morphology of S-valine functionalized MWCNTs (MWCNTs-Val) were characterized by means of field emission scanning and transmission electron microscopy (FE-SEM and TEM), Fourier transform infrared (FT-IR) spectroscopy, x-ray diffraction (XRD), and thermogravimetric analysis (TGA) measurements. The surface-modified MWCNTs showed better chemical stability in common solvents. The amino acid-containing poly(amide-imide) (PAI) composites, which had been reinforced with amino acid-functionalized MWCNTs, were fabricated using the solution blending process. Through this method, MWCNTs-Val (5–15 wt%) was dispersed in the polymer matrix by high energy ultrasound. Microstructure observations, using FE-SEM and TEM, confirmed that the fabricated composites had a good dispersion of MWCNTs-Val in the polymer matrix, and they did not agglomerate with each other. The dispersion of CNTs could be improved by the functional groups, due to the carbonyl groups on the PAI matrix itself. A thorough characterization of bionanocomposites synthesized in the present work was carried out using FT-IR, XRD, TGA, FE-SEM, and TEM techniques. The mechanical strength of the composites was also demonstrated in this work.