Functionalization of multi-wall carbon nanotubes with amino acid and its influence on the properties of thiadiazol bearing poly(amide-thioester-imide) composites

Functionalization of multi-walled carbon nanotubes (MWCNTs) with amino acid molecule using microwave irradiation, followed by reaction with a carboxylic acid moiety allows direct attachment by an amide bond. The process is fast, one-pot, simple and resulted in a high degree of functionalization as well as dispersibility in organic solvents like N,N′-dimethylacetamide. Surface functionality groups and morphology of MWCNTs were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission and transmission electron microscopy (TEM), and thermogravimetric analysis. The results consistently confirmed the formation of amino acid functionalities on MWCNTs. After that, functionalized MWCNTs (f-MWCNTs) were dispersed throughout a thiadiazol and amino acid containing poly(amide-thioester-imide) (PATEI). Through casting of these dispersions, f-MWCNT/PATEI composite films were successfully fabricated on substrates and showed no signs of macroscopic aggregation. The f-MWCNTs were dispersed homogeneously in the PATEI matrix while the structure of the polymer and the MWCNTs structure were stable in the preparation process as revealed by TEM. The PATEI and the composites were characterized by the aforementioned techniques. Tensile tests and thermal analysis were also carried out on free-standing composite films for different f-MWCNT loading levels. The results indicated that thermal and mechanical properties of the composites can be improved by hydrogen bonding interaction between the modified f-MWCNT and PATEI matrix.