Gas And Humidity Sensing Properties And Mechanism Of Electronic Polymer

Gas and humidity sensing properties and mechanism of electronic polymer are studied in this paper, which is an active field. Especially, a great deal investigation have been done on NH3 and NO2 gas sensing properties and nonlinear humidity switch effect, including some related basis questions and technology keys of electronic polymer sensitive materials, structure and properties, sensor preparation. The main research work are as follows: 1. The mechanism of polymer based conductive composite is analyzed. According swelling effect of polymer, relation between gas sensitive effect and swelling effect of polymer has been illustrated, the characteristics of polymer based composite sensing materials, principles and interfacial is first expouded, GEM equation is applied to analyze the dependence of gas sensing properties of composites on composition parameters, the following conclusions are obtained: (I) Gas and humidity sensing properties of polymer materials chiefly depend on polymer matrix, different polymer matrix should be selected for different gas (or humidity) sensor. (2) Gas (or humidity) sensing properties are closely related to conductive phase content. For certain polymer matrix, conductive phase content has a optimal value near the right of percolation 4~ relative change of composite materials resistivity reachs the most value at this point. Composite gas sensing materials have better gas sensing properties when conductive phase content lies in a very narrow range near 4~. 2. Microscopical dynamics equation of pyrrole chemical oxidation is first deducted, according to microcosmic dynamics of chemical oxidation polymerzation of pyrrole monomer(under concrete conditions). Polypyrrole submicron NH3 gas sensing films is prepared through study of polypyrrole submicron films, fitness between theory and experiment of polypyrrole chemical oxidation polymerzation dynamics shows that chemical oxidation polymerzation mechanism, pyrrole monomer microcosmic dynamics and microscopical dynamics equation which are 桰II? suggested in this paper are rational and applicable. The properties of Polypyrrole submicron NH3 gas sensing films include: 0?Oppm of concentration range; -10-60 of work temperature; response time~ 1mm; 0.O1條Op.m of film thickness.At the same time, its mechanism is analysed using semiconductor principle and interfacial absorption theory. 3. A part of raw materials for polyaniline self-assembly ultra thin films have been synthesized by chemical oxidation polymerzation and electrochemical oxidation polymerzation. The materials have been analysed and charactered using IR and UV spectrum. According properties of polyaniline ultra thin films, polyaniline self-assembly ultra thin composite sensing films are first prepared in method of doping induced deposition, its sensor function structure is designed as substrate crossed electrode ultra thin films,its NO2 sensing properties: 0梚 O0ppm of concentration range; response time<3OSec. Its sensing mechanism is analysed. 4. Nonlinear humidity sensing materials is first studied, including:cellulose polymer materials, composite humidity sensing materials, principles, technics, treating methods. The device structure of nonlinear humidity sensor is first studied. Crossed electrodes, substrate resistor type, composite films device structure and related tecbnics and treating methods are determined. The break switch point of this sensor may be firs...