Chemical and Electrochemical Synthesis of Homopolymer and Copolymers of 3-Methoxyethoxythiophene with Aniline, Thiophene and Pyrrole for Studies of Their Gas and Vapour Sensing S. Hossein Hosseini 1 * and Ali A. Entezami 2 1 Department of Chemistry, Imam Hossein Univ., Tehran-Iran 2 Polymer Lab. Faculty of Chemistry, Tabriz Univ., Tabriz-Iran ABSTRACT WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW Herein we report chemical and electrochemical formation of poly3-methoxyethoxythiophene) and its copolymers with aniline, thiophene and pyrrole which give highly conducting polymeric materials. These are soluble in common organic solvents in the conducting state. The response mechanism of these compounds, to a selection of gases and vapours, was investigated using two tech- niques: measurement of conductance and mass changes using a four probe method and X-ray fluorescence XRF) device, respectively. Prepared films were exposed to hydrogen halides, hydrogen cyanide, halogens, mono- chloroacetic acid MCAA), 1-3-5 trichloromethylbenzene TCMB), methylbenzyl bromide MBB), bromoacetone BA) and cyanogen bromide CB). These gas sensors may have advantages compared to other sensors in their ability to operate at room temperature, low concentra- tion, stability in air, sufficient diffusion and their selectivity. Copyright  2001 John Wiley & Sons, Ltd. KEYWORDS: Chemical and electrochemical poly- merization, Gas sensors, Conducting polymers, 3- Methoxyethoxythiophene, Polyaniline, Polythiophene, Polypyrrole INTRODUCTION WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW Conducting polymers such as polypyrroles or polythiophenes have been extensively studied [1± 3] and they have potential applications in various domains: battery, electrocatalytic material, electro- magnetic shielding and sensors. However, their main drawback is their insolubility. Therefore, many studies have been devoted to the develop- ment of processible conducting polymers. To that purpose, pyrrole and thiophene have been sub- stituted in 3-position by alkyl chains [4±7] and thiophene by alkyl sulfonate chains [8,9]. After polymerization of these substituted heterocycles, the polymers show indeed new properties as fusibilityorsolubility.Inthelastfewyears,another route to obtain organosoluble polymers have been developed by substituting the thiophene ring with POLYMERS FOR ADVANCED TECHNOLOGIES Polym. Adv. Technol. 12, 524±534 2001) DOI:10.1002/pat.122 * Correspondence to: S. Hossein Hosseini, Department of Chem- istry, Imam Hossein Univ., Tehran-Iran. Copyright  2001 John Wiley & Sons, Ltd. Received 8 May 2000 Accepted 18 August 2000