Alignment of carbon nanotubes in polyimide under electric and magnetic fields

Usually alignment of carbon nanotubes (CNT) in polymer composites can be induced by a single electrical or magnetic field. Here we report a comparison between the results of simultaneous application of both fields to the polyimide composite and a single field. Alignment of CNT in polyimide was performed under a 2 Tesla magnetic field and various electric fields (150, 300, 450, and 600 V/cm). Polarized Raman spectroscopy was used for assessing the degree of alignment of the nanotubes in the composites and many details of the alignment were examined. The results indicated that at the same electric field strength, incorporation of a magnetic field in a given direction will enhance the level of alignment as compared with only using an electric or magnetic field alone. The best alignment condition was for the CNT samples under parallel magnetic and electric fields. Optical microscopy observations also indicated that nanotube alignment appeared at the highest field strength and decreased when the field strength decreased. A possible mechanism for field alignment is presented. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012