| Carbon nanotubes(CNTs)/polymer composites are expected to have good processability of the polymer and excellent functional properties, owing to the superior mechanical, electrical, thermal, field-emission properties and the large aspect ratio of CNTs. Except for the challenges in uniform dispersion and interface bonding of CNTs in polymer matrix, aligning CNTs is the greatest difficulty limiting potential applications of composites, such as anisotropic functional materials, field emission display, nanoelectronic components.The quasi-straight CNTs and their bundles have been fabricated efficiently and continuously through the patent technique of our group, an arc-discharge device equipped with four graphite anodes. The extraction with toluene and a mixed nitric/sulphuric acid reflux procedure have been used to purify and functionalize the pristine CNTs. The oxidation debris, emerging in the mixed acid reflux, have been removed by the rinse and filtration with dilute NaOH (aq), diluted hydrochloric acid and deionized water repeatedly. The characterization results demonstrated that the purified quasi-straight single-walled carbon nanotubes (SWNTs) have an outstanding structural integrity and uniform diameters of close to 1.5～2.0nm, with a tube length that can be several microns. The existence of carboxyl, hydroxyl and other functional groups has been confirmed on the surface of SWNTs by FTIR. Meanwhile, it is significant that the increase in the stability of their DMF dispersions and the thermal decomposition temperature. The average yield of this purification procedure was about 60%.The in-situ bulk polymerization and a delay for the addition of SWNTs have been adopted to obtain the SWNTs/PMMA composites with a uniform dispersion, infrangible interface bonding and a high molecular weight, which are used in the electrospinning process. The electrospun setup combined with a capillary quartz tube and a rotatable cylinder collector has been assembled to realign SWNTs in the PMMA nano-fibers. The composite fibers are smooth, uninterrupted and arranged orderly with a minimum diameter of 70 nm. Under the experimental conditions, the optimum nanofiber morphologies were observed for an 8 wt% concentration solution, a 15 kV electric field, a 10 cm distance between the spinneret tip and grounded collector and a 1500 rpm rotation speed of collector. It has also been found that the temperature corresponding to the maximum decomposition rate and the electrical conductivity for the nano-fibers containing 8wt% of SWNTs increased by 62℃and 10 orders of magnitude, respectively.The blue shift of Raman spectrum for SWNTs in composites has been observed and interpreted. The formula for calculating the Hermans orientation factor S of CNTs in the non-perfectly arranged fibers has been amended and used to obtain S=0.89 in the case above, which illuminated the high alignment degree of SWNTs in composite fiber. It has been analyzed that the alignment mechanisms of CNTs in the various physical fields, the forces exerted on CNTs and the stability of alignment in the poiseuille flow inside capillary quartz tubes, as well as the orientation distribution function of CNTs in the Taylor cone at the spinneret tip.
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