Alignment of carbon nanotubes in polyimide under electric and magnetic field

Abstract

The carbon black (CB)/polyimide nanocomposite films were investigated as basic information for studying the alignment of carbon nanotubes in polyimide. The efficiently disperse carbon black in polyimide using both of surfactant and ultrasonication was prepared by two step polymerization method, with 4’4-ODA and PMDA is a starting materials. TEM images and UV-vis spectra were evidenced that the appropriate CB to surfactant ratio, which achieve to improve the transparent properties, was 1:2. Dielectric properties of the CB/polyimide nanocomposite films without surfactant increase with increasing the CB loading and decreased as the addition of surfactant. The tensile properties of the CB/polyimide nanocomposite films were improved by surfactant amount up to 1:2 of CB to surfactant ratio and were optimized at 0.5 wt% of CB in composites. Alignment of carbon natubes in polyimide was performed under the optimize condition of the CB/polyimide nanocomposites. 2 Tesla of magnetic field and various electric field, included 150, 300, 450 and 600 V/cm, were employed to induce the alignment of nanotubes in matrix. Optical microscopy observation indicated that an alignment could clearly be found when field strength is highest and would be decreased when field strength was decreased. Polarizer Raman spectroscopy was used to assess the degree of alignment of nanotubes in polyimide. At the same electric field strength, incorporation of magnetic field will be enhance the level of alignment to be better than only using electric or magnetic field alone. The three forces from electric and magnetic field were displayed important role for improving the degree of alignment in composites.