The fabrication of single-walled carbon nanotube/polyelectrolyte multilayer composites bylayer-by-layer assembly and magnetic field assisted alignment

Abstract

Single-walled carbon nanotube (SWNT)/polymer composites are widely studied because oftheir potential for high mechanical performance and multifunctional applications. In orderto realize highly ordered multilayer nanostructures, we combined the layer-by-layer (LBL)assembly method with magnetic force-induced alignment to fabricate SWNT/poly(ethylamine)(PEI) multilayer composites. The SWNTs were functionalized with the anionicsurfactant sodium dodecylbenzenesulfonate (NaDDBS) to realize negative charge atpH>7, while the PEI ispositively charged at pH<7. The LBL method is based on the electrostatic absorption between the charged SWNTsand PEI resin to form multilayer composites on a solid substrate polydimethylsiloxane.Since the fabricated thickness of each SWNT–NaDDBS/PEI bilayer is uniform (∼150 nm), the multilayer film thickness can be strictly controlled via the number of depositioncycles. A high magnetic field (8.5 Tesla) was used to align the SWNTs during the LBLprocess. The resultant LBL composite samples demonstrated high SWNT loading ofapproximately 50 wt% and uniform distribution of SWNTs in the multilayer structures,which was verified using a quartz crystal microbalance. Good alignment was alsorealized and observed through using high magnetic fields to align the nanotubesduring the LBL deposition process. The results indicate that the LBL/magneticalignment approach has potential for fabricating nanotube composites with highlyordered nanostructures for multifunctional materials and device applications.