Mechanical and morphological characterization of polymer–carbon nanocomposites from functionalized carbon nanotubes M.C.Paiva a, * ,B.Zhou a,b ,K.A.S.Fernando a,b ,Y.Lin a,b ,J.M.Kennedy a,c ,Y.-P.Sun a,b a Center for Advanced Engineering Fibers and Films, Clemson University, Clemson, SC 29634-0910, USA b Department of Chemistry, Clemson University, SC 29634, USA c Department of Mechanical Engineering, Clemson University, SC 29634, USA Received 29 February 2004; accepted 22 June 2004 Available online 14 August 2004 Abstract Carbonnanotubeswerefunctionalizedwithpoly(vinylalcohol)(PVA).Thewater-solublePVA–functionalizedcarbonnanotubes were then embedded into PVA matrix via a wet-casting method, resulting in polymer–carbon nanocomposite films with homoge- neous nanotube dispersion. Composites with pristine and functionalized nanotubes were tested in tension. It was found that the mechanical properties of these nanocomposite films were significantly improved compared to the neat polymer film. Functionaliza- tionallowedgooddistributionofthenanotubesinthematrix,leadingtohigherfilmstrength.Scanningelectronmicroscopyshows anapparentgoodwettingofthenanotubesbythePVAmatrix.Theseresultsaresupportiveofgoodinterfacialbondingbetweenthe functionalized carbon nanotubes and the hosting polymer matrix. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: A. Carbon composites, Carbon nanotubes; C. Electron microscopy, Raman spectroscopy; D. Mechanical properties 1. Introduction Therehasbeenintenserecentresearchconcerningthe fabrication, characterization and application of poly- mer–carbon nanotube composites, driven by a growing recognitionoftheuniquemechanical,electrical,thermal andothermaterials-relatedpropertiesofcarbonnanotu- bes [1,2].Inthefabricationofhigh-qualitypolymer–car- bon nanocomposites with predictable and optimal performance, a homogeneous dispersion of the carbon nanotubesinthepolymermatrixisrequired.Methodol- ogies such as sonication of carbon nanotubes in a poly- mer solution [3,4] and in situ polymerization in the presence of carbon nanotubes [5,6] were developed for the homogeneous dispersion of the nanotubes in the polymer matrix. Presently, the chemical functionaliza- tion and solubilization of carbon nanotubes has emergedasaneffectivemeansforthehomogeneousdis- persionofcarbonnanotubesinsolutionandforthesub- sequent wet-casting of polymer–carbon nanocomposite films [7]. Improvement in the compatibility between the functionalized carbon nanotubes and the hosting polymer matrices have been discussed. For example, Tour, Krishnamoorti and coworkers reported the func- tionalization of single-walled carbon nanotubes (SWNTs) with diazonium salts, and the functionalized SWNTs were used to form polystyrene-based compos- ites [8]. These nanocomposites were found to have a lower percolation threshold than those obtained with pristine SWNTs. Sun and coworkers reported the func- tionalizationandsolubilizationofSWNTsandmultiple- walled carbon nanotubes (MWNTs) with polystyrene 0008-6223/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2004.06.031 * Corresponding author. Present address: Department of Polymer Engineering, Institute for Polymers and Composites, University of Minho,CampusofAzure ´m,4800-058Guimara ˜es,Portugal.Tel.:+351 253510327; fax: +351 253510339. E-mail address: mcpaiva@dep.uminho.pt (M.C. Paiva). Carbon 42 (2004) 2849–2854 www.elsevier.com/locate/carbon