Electrical Conductivity of Polymer Blends of Poly(3,4- ethylenedioxythiophene) : Poly(styrenesulfonate) : N-Methyl-2-pyrrolidinone and Polyvinyl Alcohol Chang-hsiu Chen, 1 John C. LaRue, 2 Richard D. Nelson, 3 Lawrence Kulinsky, 2 Marc J. Madou 1,2,4,5 1 Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697 2 Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697 3 Department of Electrical Engineering and Computer Science, University of California, Irvine, California 92697 4 Department of Biomedical Engineering, University of California, Irvine, California 92697 5 Ulsan National Institute for Science and Technology, World Class University, Ulsan, South Korea Received 22 January 2011; accepted 11 November 2011 DOI 10.1002/app.36474 Published online 1 February 2012 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: The goal of this study is to determine the electrically conductivity of the polymers poly(3,4-ethylene- dioxythiophene) : poly(styrenesulfonate) : N-methyl-2-pyr- rolidinone (PEDOT : PSS : NMP) and PEDOT : PSS when blended with polyvinyl alcohol (PVA). While the conduct- ing polymers have high conductivity when not blended with PVA, they are brittle and difficult to spin-coat. Thus, the motivation for this study is to develop blends of these two conducting polymers with PVA to produce a material with optimized mechanical properties and that can also be spin-coated. The blends are produced using aqueous prep- arations of these materials. Mixtures of various weight percentages (wt %) of PEDOT : PSS : NMP and PEDOT : PSS are prepared and spin-coated on glass slides to form thin films. In the blends, the film conductivity increases with increasing content of either PEDOT : PSS : NMP or PEDOT : PSS. For example, 100 wt % of PEDOT : PSS : NMP and 60 wt % of PEDOT : PSS : NMP blended with PVA ex- hibit conductivities of, respectively, 10 and 4.02 S/cm. In contrast, conductivities of only 0.0525 and 0.000506 S/cm are observed, respectively, for 100 wt % of PEDOT : PSS and 60 wt % of PEDOT : PSS content in the PEDOT : PSS/PVA blends (No NMP). The addition of the NMP enhances the electrical conductivity by two to five orders of magnitude (depending on the amount of PVA in the blend) due to con- formational change of PEDOT chains. V C 2012 Wiley Periodi- cals, Inc. J Appl Polym Sci 125: 3134–3141, 2012 Key words: MEMS; PEDOT; PEDT; polyvinyl alcohol; NMP; conducting polymers; conductivity enhancement INTRODUCTION Throughout the past two decades, the field of micro- electromechanical systems (MEMS) has been grow- ing rapidly. 1 It is recognized that the rate of future growth in MEMS applications depends, in part, on the development of the novel functional materials, including polymers. 2 Low cost, easy processing, excellent thermal stability, relatively high flexibility, ability to fabricate films 1–10 lm thick, and low Young’s Modulus provide the motivation for the de- velopment of synthetic polymer materials for MEMS. Development of conducting polymers 3,4 sparked a wide variety of applications and novel devices in the fields of microelectronics, 5 electrolu- minescence, 6,7 optical amplifiers, 8,9 and organic transistors. 10,11 Single component polymers such as polypyrrole, polyimide, poly(3,4-ethylenedioxythiophene) (PEDOT), polydimethylsiloxane, poly(methyl methacrylate), and polyvinyl alcohol (PVA) have found a wide va- riety of applications in MEMS devices. Additionally, blending of polymers offers means to combine the useful and desired properties exhibited by the indi- vidual polymer components with a concomitant enhancement of selected properties. For example, PEDOT, 12–14 a conducting polymer used in organic light-emitting diodes and organic transistors, has high electrical conductivity (up to 500 S/cm) in the doped state, as well as good thermal and chemical stability. 15 However, PEDOT is insoluble in water and is difficult to process, but when polystyrene sul- fonic acid (PSS) (which serves as the charge-balanc- ing dopant during polymerization) is added to the mix, the PEDOT : PSS blend forms a highly stable dispersion in water that contributes to ease of proc- essing. In the PEDOT : PSS complex, oligomeric PEDOT segments are tightly attached to PSS chains by means of electrostatic forces. 16 This molecular Correspondence to: C.-h. Chen (changhsc@uci.edu). Contract grant sponsor: National Science Foundation (L.K. and M.M.); contract grant numbers: ECCS 0801792, CBET 0709085. Contract grant sponsor: UC Lab Fees Award (L.K. and M.M.); contract grant number: 09-LR-09-117362. Journal of Applied Polymer Science, Vol. 125, 3134–3141 (2012) V C 2012 Wiley Periodicals, Inc.