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In recent years,with the fast development of science and technology, it provides tremendous convenience to human beings.But at the same time,it has seriously polluted the enviroment.Owing to the toxic and flammable gases threat to our health and wealth,human beings call for a high-qualiy environment.So it becomes more and more important in the study of gas sensor to detect and inspect the toxic and flammable gases. Now the main problem in the research and development is that high-sensitivity,normal-temperature,fast-response,good-selectivity, extended-stability can’t meet at the same time.Recently,the research and development focus on how to enhance the sensitivity,selectivity and stability,reduce the temperature,and shorten the response-recovery time.Now,a lot of work has been done in the research of MOS in our courtry,such as SnO2、Fe2O3、ZnO、TiO2,and organic polymer conductors, including the conjugated polymers and polymer composites,such as polypyrrole,polyaniline,phthalocyanin,polythiophene,composite of polymers with carbon black,composite of poly（vinyl alcohol）with polyaniline,etc.Inorganic semiconductors have recently attracted a great deal of attention for application in gas sensors.But there are still many disadvantages,such as high temperature（350～450℃）,energy-waste, unsafety,bad-selectivity,etc.The organic polymer conductor has more advantages when compared with the inorganic semiconductors,such as low-price,and easy-made.When prepared,we don’t need super clean room and high temperature treatment,what is more important,it can operate in room temperature avoiding the unsafety of flammable gases.In this work we investigate the properties of gas sensors made from PEO with good water-solubility,easy-shape and low-toxicity.As an unconjugated and insulated polymer,there are several reportes about its composites with conjugated polymers as gas sensing materials in foreign literature.However,there is little report about the application of pure PEO in gas sensor.In the paper,we prepare the films of PEO and PEO doped with I2 by solution and study the gas sensitivity of alcohols and organic acids in room temperature,including the sensitivity,selectivity, response-recovery time and stability.The corresponding morphology characterizations including SEM, AFM and Polarizing Microscope show that the spherulites of PEO grow and swell when the film of PEO dipping into the vapors of alcohols and organic acids.Hydrogen bond is formed when PEO dipped in methanol which is cleaty shown m the FTIR.And from the cyclic voltametry spectra,we fred there is no oxidation-reduction reaction when the thin-film of PEO dipped in the organic acids.Finally,the mechanism of the ionic conduct is confirmed according to the analysis of the impendance spectra.Furtherly,we stndy the gas=sensing properties of the film PEO doped with I2.However,the gas-sensing properties don’t improved when compared with the PEO.Morphology characerization show that the film PEO doped with I2 becomes swelling and there is no observation of a continuous conduct channel of I2.
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