Synthesis, characterization, and enhanced properties of novel graphite-like carbon nitride/polyimide composite films

In this article, polyimide (PI) composite films reinforced by graphitic carbon nitride (g-C 3 N 4 ) have been synthesized using the in situ polymerization process via thermal imidization. Poly (amic acid) (PAA) solutions were prepared from pyromellitic dianhydride (PMDA) and 4,4′-(4,4′-isopropylidenediphenyl-1,1′-diyldioxy) dianiline (BAPP) in N,N-dimethylacetamide (DMAc) solvent. The different amounts of g-C 3 N 4 obtained from the direct pyrolysis of dicyandiamide (DCDA) at 600°C were incorporated into PAA matrix, which formed g-C 3 N 4 /PI composite films by thermal imidization. The morphological structures of the synthesized g-C 3 N 4 and g-C 3 N 4 /PI composite films were characterized using fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy and transmission electron microscopy. With 2 wt% g-C 3 N 4 incorporated, the tensile strength and elongation at break of g-C 3 N 4 /PI composites were increased by about 23% and 21%, respectively, due to the strong interaction between the g-C 3 N 4 particles and PI. Thermogravimetric analysis indicated that the incorporation of g-C 3 N 4 improved the thermal stability of the PI at low g-C 3 N 4 content. Besides, the dielectric and optical properties of these composites were also studied in this article.