Synthesis and Electrophoretic Deposition of Single-Walled Carbon Nanotube Complexes with a Conjugated Polyelectrolyte

A conjugated tertiary amine-functionalized polymer, poly(9,9-bis(diethylaminopropyl)-2,7-fluoreneco-1,4-phenylene), was synthesized and employed in the supramolecular functionalization of single-walled carbon nanotubes. The formation of stable solutions in organic solvents, as well as in water upon protonation of the amine groups, indicates strong supramolecular interactions between the polymers and the carbon nanotube surface. UV-vis absorption spectroscopy and Raman spectroscopy were utilized to characterize the resulting functionalized nanotubes and it was found that the nanotube structure was unchanged due to the nature of noncovalent functionalization, thus preserving the nanotube's,inherent properties. Electrophoretic deposition techniques were developed to create uniform films of this polymer and also a mixture of the polymer with the supramolecularly functionalized carbon nanotubes. The deposition mechanism involves the electrophoresis of the charged polymer species in an acid solution followed by the charge neutralization of the polymer species at the high pH region of the cathode surface. Scanning electron microscopy was used to visualize cross sections of the films as well as the film surfaces, showing uniform coatings that are free of cracks but contain small pores having diameters below 100 nm. The deposition rate was measured using a quartz crystal microbalance and found to vary with voltage and solution concentration. Control over film thickness was demonstrated in the range of approximately 100 nm to 10 mu m.