Mechanically robust biocomposite films of chitosan grafted carbon nanotubes via the [2 + 1] cycloaddition of nitrenes
Chitosan functionalized multiwalled carbon nanotubes (CS-MWCNTs) are prepared using the [2 + 1] cycloaddition of nitrenes to the π electron system of carbon nanotubes followed by an amidation reaction with chitosan. The analysis of transmission electron microscopy (TEM) micrographs suggests the presence of more than 14 nm of chitosan grafted onto the MWCNTs, and the covalent linkage of chitosan with the MWCNTs is confirmed from FTIR and Raman spectra, XPS and energy dispersive X-ray spectroscopy (EDS) elemental mapping. The grafting density calculated using thermogravimetric analysis was 1.8 chitosan chains per 1000 MWCNT carbons. The effectiveness of the biofunctionalized CS-MWCNTs as a reinforcing filler (3 wt%) in a chitosan polymer matrix was verified by the dramatic enhancement of the mechanical properties (the tensile strength of the composite is significantly increased to 81.3 MPa from 36.5 MPa for pure chitosan, the highest modulus was up to 4.4 GPa for the composite with 3 wt% CS-MWCNTs) with a high elongation-at-break. The interfacial bonding between the CS-MWCNTs and the chitosan matrix plays a crucial role in the enhancement of the physical performance of the MWCNT-based composites.