Preparation and Characterization of Electrospun Fibers of Poly (methyl methacrylate) - Single walled carbon nanotube Nanocomposites

Electrospinning is a versatile method of preparing polymer nanocmposite fibers. Electrospun nanocomposite fibers of poly(methyl methacrylate) and single walled carbon nanotubes were prepared. The fibers were characterized by SEM, TEM, TGA and Raman spectroscopy. These fibers show dramatic improvement in the electrical conductivity compared to the polymer. The temperature dependent electrical resistance measurements show a one dimensional variable range hopping model (1-D VRH) type of conduction mechanism operating in these types of systems. INTRODUCTION Electrospinning is a method of producing fibers with diameters in the range of 10 μm to 10 nm by accelerating a charged polymer jet in an electric field [1-5]. This method has attracted much attention due to the ease with which such nano fibers can be produced from either natural or synthetic polymers. Such small fibers have numerous and diverse applications including filtration and composite materials. The large surface area to volume ratio of nanofibers makes them attractive as catalyst supports, sensors and in drug delivery. Electrospun nonwoven fabrics are being developed as scaffolds in tissue engineering. Electrospun conducting polymers have been used to fabricate nanowires. Since their discovery by Iijima, carbon nanotubes (CNTs) have gained widespread attention due to their unique structure and extraordinary physical properties [6, 7]. A single walled carbon nanotube (SWNT) can be described as a single graphene sheet rolled into a tube. These tubes are either semi conducting or metallic depending on their chirality and diameter. Exceptional mechanical and electrical properties of SWNTs, as well as their high aspect ratio and low density, make them ideal candidate as fillers for developing lightweight multifunctional and structural polymer composites. Polymer composites containing carbon nanotubes are of great interest because they may possess a novel combination of electrical, optical and mechanical properties. Polymer composites with carbon nanotubes have recently been investigated for improved electrical conductivity, optical devices and high strength composites. However, the realization of the excellent properties of carbon nanotubes is hampered due to the processing difficulties. Due to strong van der Waal forces between the CNTs, it is very difficult to disperse them uniformly in polymer solution. Several approaches have been reported for obtaining stable CNT dispersion [8-10]. Electrospinning is an ideal method for preparation of nanofibers of polymer composites with CNTs as filler. Till date several reports have been published on such composites with CNTs with different polymers [11-19]. Using the electrospinning method, Chang et al. have prepared SWNT/polyvinylidenefluoride (PVDF) fiber mats and investigated the percolation threshold for the insulator-to-conductor transition of the composite mats. Ko et al. have prepared continuous CNT-filled nanofibers (NFs) and reported that the elastic modulus has improved by120% in NFs containing 4 wt% SWNTs. Dror and Salalha et al., have achieved well-dispersed multiwalled carbon nanotubes (MWNTs) and SWNTs and successfully prepared the electrospun MWNT/PEO NFs in which MWNTs can be observed using transmission electron microscopy (TEM). Recently, Ge and Hou, et al. have prepared highly-oriented, large area continuous MWNTs -polyacrylonitrile (PAN) NF composite sheets and reported that, for the first time, the orientation of the MWNTs within the NFs was much higher than that of the PAN polymer crystal matrix. PMMA is a thermoplastic having excellent processiblity, optical properties and environmental stability, which makes it one of the best candidates for matrix in CNT-based nanocomposites.