Structure and properties of polyacrylonitrile/single wall carbon nanotube composite films Huina Guo, T.V. Sreekumar, Tao Liu, Marilyn Minus, Satish Kumar * School of Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, P.O. Box 0295, Atlanta, GA 30332, USA Received 4 December 2004; received in revised form 5 February 2005; accepted 9 February 2005 Available online 9 March 2005 Abstract Polyacrylonitrile (PAN)/single wall carbon nanotube (SWNT) composite films have been processed with unique combination of tensile strength (103 MPa), modulus (10.9 GPa), electrical conductivity (1.5!10 4 S/m), dimensional stability (coefficient of thermal expansion 1.7!10 K6 /8C), low density (1.08 g/cm 3 ), solvent resistance, and thermal stability. PAN molecular motion above the glass transition temperature (T g ) in the composite film is significantly suppressed, resulting in high PAN/SWNT storage modulus above T g (40 times the PAN storage modulus). Rope diameter in the SWNT powder was 26 nm, while in 60/40 PAN/SWNT film, the rope diameter was 40 nm. PAN crystallite size from (110) plane in PAN and PAN/SWNT films was 5.3 and 2.9 nm, respectively. This study suggests good interaction between PAN and SWNT. q 2005 Elsevier Ltd. All rights reserved. Keywords: Polyacrylonitrile; Single wall carbon nanotube; Nanotube 1. Introduction SWNTs possess high intrinsic strength, stiffness, and electrical conductivity [1,2], and are being incorporate in polymers to obtain composites with unique properties. Various matrix systems that have been studied for this purpose include: poly(vinyl alcohol) (PVA) [3–5], poly (methyl methacrylate) [6–9], poly(m-phenylenevinylene- co-2, 5-dioctoxy p-phenylenevinylene) [10], polypropylene [11], epoxy [12,13], poly(3-octylthiophene) [14,15], poly- imide [16,17], polycarbonate [18], polystyrene (PS) [19,20], polyaniline [21], polypyrrole [22], alkoxysilane terminated amide acid (ASTAA) [23], PAN [24,25], and poly(p- phenylene benzobisoxazole) [26]. Most of these studies have been carried out at nanotube loadings generally below 10 wt%. However, several studies at high nanotube loadings have been reported. For example, exceptionally tough PVA fibers with 60 wt% SWNTs have been processed [27]. Polyelectrolyte film with 50 wt% SWNT resulted in a tensile strength of 220 MPa [28]. Improvements in modulus, strength, and toughness of SWNT films have been reported with PVA or PS infiltration [29]. PAN, a commercially important polymer and carbon precursor [30], is generally processed from solution [31]. Carbonized PAN/SWNT films are good candidates for electrochemical supercapa- citor electrodes [32]. Here, we report PAN/SWNT films with unique combination of tensile, electrical, and thermo- mechanical properties, low density, and solvent resistance. 2. Experimental Unpurified HiPCO SWNTs (catalytic impurity based on the thermogravemetric analysis was about 30 wt%) obtained from Carbon Nanotechnologies Inc. were used as received. Dimethyl formamide (DMF) and polyacrylonitrile containing 10% methyl acrylate (random copolymer, molecular weight 100,000 g/mol) were purchased from Sigma-Aldrich and were also used as received. Vacuum dried 0.137 g SWNTs were dispersed in 50 ml DMF by a combination of sonication (Cole-Parmer 8891 bath soni- cator) and homogenization using a bio-homogenizer (Biospec products Inc. M133/1281-0). To this SWNT/DMF dispersion, 0.2055 g PAN was added and dissolved by stirring. The PAN/SWNT/DMF solution was cast onto a hot Polymer 46 (2005) 3001–3005 www.elsevier.com/locate/polymer 0032-3861/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2005.02.013 * Corresponding author. Tel.: C1 404 894 7550. E-mail address: satish.kumar@ptfe.gatech.edu (S. Kumar).