Role of Polymer–Salt–Solvent Interactions in the Electrospinning of Polyacrylonitrile/Iron Acetylacetonate Jinmei Du, Xiangwu Zhang Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry, and Science, North Carolina State University, Raleigh, North Carolina 27695-8301 Received 21 December 2007; accepted 6 March 2008 DOI 10.1002/app.28396 Published online 20 May 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Electrospinning is a process of producing ultrafine fibers by overcoming the surface tension of a poly- mer solution with electrostatic force. In this study, iron ace- tylacetonate was added to a polyacrylonitrile solution, and the role of polymer–salt–solvent interactions in the electro- spinning of the ultrafine fibers was investigated. The poly- mer–salt–solvent interactions were characterized by Fourier transform infrared spectroscopy; and the solution viscosity, conductivity and surface tension were measured in solu- tions with different salt concentrations. The formation of polymer–salt–solvent interactions increased the solution vis- cosity, conductivity, and surface tension values at low salt concentrations. At high concentrations, the solution viscos- ity and surface tension decreased, but the conductivity remained relatively constant. The polymer–salt–solvent interactions influenced the structures of the electrospun fibers by changing the balance among the solution viscosity, conductivity, and surface tension. Ó 2008 Wiley Periodicals, Inc. J Appl Polym Sci 109: 2935–2941, 2008 Key words: association; composites; fibers; nanocompo- sites; nanotechnology INTRODUCTION Electrospinning is a relatively versatile, flexible, and easy method for producing ultrafine fibers with diameters ranging from 20 nm to 1 lm, and these fibers have a wide variety of applications, such as scaffolds for tissue engineering, filter media, protec- tive clothing, capacitors, battery separators, and fuel cells. 1–5 Many polymers have been electrospun into ultrafine fibers, including polyacrylonitrile (PAN), polyethylene, polycarbonate, polystyrene, poly(vinyl alcohol), and collagen. 6,7 Among these polymers, PAN has been widely used to produce fine fibers because of the high dielectric constant that is desira- ble for electrospinning and many other applica- tions. 8–10 PAN also provides well-known routes to carbon fibers, which can be used in many applica- tions, such as sensors, catalyst supports, and bat- teries. 8 Compared with other polymer carbon pre- cursors, PAN has advantages of a high carbon yield and flexibility in the control of the structure and properties of the final carbon fiber products. 11–13 In addition, salts are often added to the PAN precur- sors to obtain active carbon fibers. 14 Many efforts have been carried out to study the electrospinning process, including studies on the effects of voltage, feed rate, and needle–collector dis- tance. 15–17 However, there is less information in the literature about the role of polymer–salt–solvent interactions in the electrospinning of polymer fibers. 18 The addition of salts can introduce compli- cated polymer–salt–solvent interactions and can change solution properties, such as viscosity, con- ductivity, and surface tension. 19–22 The diameter of electrospun fibers is largely determined by the bal- ance between the viscoelastic forces, electrostatic repulsion (conductivity), and surface tension. 23 Qin et al. 18 found that the addition of salts can change the viscosity of PAN solutions and the diameter of the resulting electrospun PAN. However, the influ- ence of salt on other solution properties, such as con- ductivity and surface tension, was not addressed. In this study, the polymer–salt–solvent interactions of PAN and iron acetylacetonate (AAI) solutions in N,N-dimethylformamide (DMF) were investigated. Their relationships to the solution properties, such as viscosity, conductivity, and surface tension, and the resultant fiber structure were established. EXPERIMENTAL Materials AAI (purity 5 99.9%), PAN (weight-average molecular weight 5 150,000, typical), and DMF (purity 5 99.8%) were purchased from Sigma-Aldrich (Milwaukee, WI). They were used without further purification. Correspondence to: X. Zhang (xiangwu_zhang@ncsu.edu). Journal of Applied Polymer Science, Vol. 109, 2935–2941 (2008) V V C 2008 Wiley Periodicals, Inc.