Electron beam modification and functionalization of MWNT for covalent dispersion into polymeric systems Mary E. Sullivan a , Don Klosterman b , Giuseppe R. Palmese a, * a Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, United States b University of Dayton Research Institute, Dayton, OH 45469, United States Available online 8 September 2007 Abstract The development of nanotube-based polymer composites with improved mechanical properties and electrical conductivity requires the covalent dispersion of carbon nanotubes to utilize their stress transfer capabilities. Covalent dispersion of nanotubes therefore requires the functionalization of their surface to interact with solvents or monomers. In this work, we have developed a novel method of nanotube surface modification in which dry MWNT are irradiated with a high-energy electron beam (EB) in ambient air environment. Raman spectroscopy was performed to characterize the influence of EB irradiation on nanotubes, namely, variance of the disorder, or D band (1360 cm 1 ) with respect to the graphitic, or G, band (1580 cm 1 ). Raman spectra show increased deformation to the graphitic structure, as well as increased strain on the carbon–carbon bonds, weakening the nanotube. Transmission electron microscopy (TEM) confirms that nanotubes remain intact despite high EB dose. In addition, minimal surface deformation and length reduction occurred on irradiated MWNT. Ó 2007 Elsevier B.V. All rights reserved. PACS: 61.80.Fe Keywords: Carbon nanotubes; Surface modification; Raman spectroscopy; Transmission electron microscopy 1. Introduction The discovery of multiwalled carbon nanotubes (MWNT) in 1991 [1] and singlewalled nanotubes (SWNT) in 1993 [2] has allowed for the development of structural and conductive reinforcement fillers for polymers and elec- tronic systems. Due to their small diameter, high aspect ratio, strength, and conductive and semi-conductive prop- erties, nanotubes are excellent reinforcing fillers for systems requiring enhanced electrical or material properties and may disperse into such systems at low percolation concen- trations. However, despite their potential for enhanced composites properties, van der Waals interactions between nanotubes as well as their highly stable graphitic structure render them insoluble in water, organic solvents and most monomers. As a result, nanotubes separate from solution, and their excellent material properties are not realized on a macroscopic scale. Furthermore, in order for nanotube- reinforced systems to be structurally enhanced (allowing for load transfer from the bulk material to the nanotube fil- ler), covalent interactions between nanotubes and the poly- mer chains are preferred [3]. Without their covalent dispersion into a polymer system, their high strength and elasticity provide little improvement to the material proper- ties of the system. Various methods of chemical modifica- tion of nanotubes are being conducted to covalently disperse nanotubes into different media. However, many of these methods induce high deformation to the nanotubes graphitic structure, which may damage or destroy the nanotube. Such methods include irradiation through focused a transmission electron microscope (TEM) beam [4,5] and inorganic acid oxidation [6]. 0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.09.002 * Corresponding author. Tel.: +1 215 895 5814; fax: +1 215 895 5837. E-mail address: palmese@coe.drexel.edu (G.R. Palmese). www.elsevier.com/locate/nimb Available online at www.sciencedirect.com Nuclear Instruments and Methods in Physics Research B 265 (2007) 352–355 NIM B Beam Interactions with Materials & Atoms