Electrically Conductive Sensors for Liquids Based on Quaternary Ethylene Vinyl Acetate (EVA)/Copolyamide/ Maleated-EVA/Polyaniline Blends H. Cooper, E. Segal, S. Srebnik, R. Tchoudakov, M. Narkis, A. Siegmann Department of Chemical Engineering and Department of Materials Engineering, Technion, IIT, Haifa 32000, Israel Received 7 March 2005; accepted 27 March 2005 DOI 10.1002/app.21969 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Electrically conductive blends, containing two immiscible polymers (ethylene vinyl acetate copolymer, EVA-19, and copolyamide 6/6.9, CoPA), polyaniline (PANI), and maleated EVA compatibilizer were studied as sensing materials for a homologous series of alcohols (meth- anol, ethanol, and 1-propanol). Recent results have shown that the corresponding uncompatiblized blends exhibited a preferred localization of PANI in the CoPA phase, leading to a cocontinuous morphology (i.e., both the CoPA phase and the PANI component located in it are continuous). The concept of the compatibilizer addition was to improve com- patibility between the EVA-19 and the CoPA, modifying the morphology of the PANI-containing blend and altering its sensing properties. Extruded EVA-19/CoPA/maleated- EVA/PANI filaments produced by a capillary rheometer process at various shear rate levels were used for the sensing experiments. The filaments displayed high sensitivity levels upon exposure to the various alcohols as well as improved sensing stability and reproducibility at low compatibilizer contents. The sensing properties vary with compatibilizer concentration and are of inferior quality beyond a certain content. The sensing behavior of the compatibilized fila- ments is compared to the previously reported results for the corresponding uncompatibilized filaments. © 2006 Wiley Pe- riodicals, Inc. J Appl Polym Sci 101: 110 –117, 2006 Key words: sensors; plastics; blends; conductivity INTRODUCTION The increasing concern of environmental pollution and health or fire hazards due to various chemicals used in industry, together with the widespread re- quirements for more accurate process control, has cre- ated a need for new or improved sensing elements for measuring both physical and chemical parameters. 1,2 Intrinsically conductive polymers (ICPs) have been suggested as an effective medium for chemical sens- ing of airborne volatile compounds. Such conductive polymers offer chemical sensing ability due to elec- tronic (conductivity) changes, arising with adsorption of the volatile compounds (analytes), and which are commonly attributed to the interaction of the electron- ically active analytes with either the polymer back- bone itself or the dopant molecules incorporated within the polymer, thereby modulating the mobility and/or the number of available free charge carriers. 3 There are numerous studies on ICP/polymer blends reported in the literature. These studies concluded that the ICP/polymer blends combine the advanta- geous mechanical properties of the host polymer with the electrical properties of the ICP. Thus, in the past few years, special attention has been focused on the application of ICP/polymer composites or blends as sensing materials. The responses of the blends are better defined compared with the neat conducting polymer. 2,4–8 Recently, the sensing behavior of melt-processed polyaniline (PANI) containing immiscible polymer blends of ethylene vinyl acetate copolymer (EVA)/ copolyamide 6/6.9 (CoPA) has been studied. 9 These blends were designed to have a double-percolation structure. The PANI phase showed a preferred lo- calization within the minor-continuous CoPA phase, thus enhancing the formation of continuous conducting networks. A series of electrically con- ductive blends’ filaments was produced by a capil- lary rheometer process. Liquid immersion/drying cycling of the filaments showed relatively high sen- sitivity and selectivity toward the studied liquids; however, the filaments’ rate of production signifi- cantly affects the relative resistance change and their reproducibility. An attempt to improve the sensing properties of these filaments can be done by Correspondence to: M. Narkis (narkis@tx.technion.ac.il). Contract grant sponsor: U.S.–Israel Binational Science Foundation. Contract grant sponsor: Levi Eshkol Scholarship from the Israel Ministry of Science. Journal of Applied Polymer Science, Vol. 101, 110 –117 (2006) © 2006 Wiley Periodicals, Inc.