Hydroxy-modified Conductive Polymer Organic Phosphine Poison Gas Sensing Properties Of Sensitive Materials

The chemical terrorism cases frequently happened in 20th Century caused great harm to the masses. Thus, it is very important to develop detectors and sensors that are able to warn about imminent chemical warfare agents(CWA) danger,to enable people to safely leave a contaminated zone or to protect themselves.The mass-sensitive chemical sensors have been widely used as detections of CWA over the last years due to small size and high sensitivity. And the performance of sensors is greatly affected by the sensitive materials. Compared to traditional inorganic semiconductor materials, conductive polymer material has a cheap, simple deposition process and low environmental requirements. It is the most important that the conductive polymer material can be deposited on various substrates, and can choose different structure of macromolecular chain. Furthermore, conductive polymer can get different sensitivity by chemical modification to improve its response sensitivity and selectivity. There were many kinds of hydrogen bond acidic materials which were used to detect the hydrogen bond basic gases such as never agents, but these materials were not conductive. Therefore, in this thsis conductive polymer with hydrogen bond acidic groups was proposed as the sensing polymers for nerve agents detection. Firstly, a great deal investigations have been done on the synthesis of hydroxyl groups modified conducting polymer. Then the sensitivity and conductivity of different materials were measured by Quartz Crystal Microbalance (QCM) and Interdigital Transducer (IDT) sensors. The main researchs were as follows:(1) According to the basic ideals of hydroxyl groups modified conducting polymer, poly(o-aminophenol) (POAP) were polymerized by o-aminophenol (OAP) and co-polymer were prepared by copolymerized with aniline (ANI). The polymer POAP has the similar structure with PANI, while there are hydroxyl groups on the benzene ring. Polyaniline (PANI) films, POAP films and poly(aniline-co-o-aminophenol) films were prepared by electrochemical method. The cyclic voltammogram showed that ANI and OAP can be copolymerized and the polymer films have good conductivities. But the hydroxyl groups which we needed were oxidized by the currents when the monomers were polymerized. Three kinds of films were prepared on QCM sensors which were used as the work electrode. Then the sensitivity to DMMP vapors was researched. The result showed that the POAP film sensors didn't response to DMMP at all, while the PANI films and copolymer films have low response. The conductive of different polymers were also tested.(2) Because the hydroxyl groups can be easily oxidized in the polymerization process, a new synthesis routine was proposed. To prevent the oxidization of the hydroxyl groups, the synthesis process should include at least three steps: 1) modify the molecular structure of the monomer to protect the hydroxyl groups before polymerization, 2) synthesize the conducting polymers by oxidizing, 3) remove the protection on the hydroxyl groups. According to this process, poly(3,4- dihydroxythiophene) was synthesized from 3,4-ethylenedioxythiphone (EDOT) monomer. The films were characterized by FTIR, and the Spectrum analyses indicated that the polymer have the similar structure with polythiophene, while there are hydroxyl groups on the thiophene ring. Then the polymer films were prepared on QCM sensors, and the sensitivity to DMMP vapors was researched. The polymer films sensors showed good response to DMMP, and the sensitivity of the sensors was greatly affected by the concentration of vapors and the thickness of film. However, the film sensors were hard to return to the initial frequencies after the absorption, and the responses decreased after the sensors were exposed to air for a long time. Then, the selectivity of the sensors were tested in several organic vapors and good selectivity to DMMP was confirmed. The polymer materials were also spinned on the IDT to test the gas sensetive properties. The result showed that the polymer have good conductivity, and the conductivity was affected by adsorbing the DMMP vapors..