a nabipour - Materials Research School, NSTRI, Karaj, Iran,
b Zhang - ۲Center for Composite Materials,HIT, Harbin, China,
m Amirian - Teachers University, Ferdosi Center, Karaj, Iran
y Li - ۲Center for Composite Materials,HIT, Harbin, China,

An aromatic polyimide (PI) with rigid benzoxazole backbone and rigid bulky trifluoromethyl (-CF3) side group has been developed as matrix for in-situ polymerized carbon nanotube (CNT) reinforced nanocomposites. Due to the presence of bulky side group CF3 in the PI backbone, CNTs were carboxylated to engineer the interface between matrix and CNTs by covalent bond. Electron microscopy reveals that a homogeneous dispersion of individual nanotubes in their host PI matrix can be achieved with COOH groups attached on the CNT surface. Fourier transform infrared spectroscopy indicated the formation of covalent bonds between CNTs and PI chains. More significant increase in both elastic modulus and tensile strength was achieved in CNT-COOHs/PI nanocomposites than that of pristine CNT/PI nanocomposite. SEM images of the fracture surface suggest that the COOH groups on the CNT surface improve the nanoscale dispersion of nanotubes in PI matrix and their interfacial adhesion by creating chemical bond between CNTs and PI matrix. The thermal stability of nanocomposites is more greatly enhanced by addition of CNT-COOHs in comparison with pristine CNTs

Carbon nanotubes, Nanocomposites, Polyimide, Benzoxazole, In-situ Polymerization