Preparation Of Polyaniline And Relative Derivatives And Their Humidity Sensing Properites

With the development of the modern industry and the increasing of people's living, the measurement and control accuracy of humidity put forward the higher demands. Therefore, it is increasing becoming importance to exploiture the high-performance, long-life humidity sensors. Compared with inorganic materials, macromolecule humidity materials own to easy preparation and processing. Furthermore, different physical and chemical properties material can be gaind through the molecular structure modified. It is received more attention due to abundance source of materials, wide range of relative humidity, small hysteretic of humidity and fast response.As the most investigated conducting polymers, polyaniline (PANI) and its derivtives have attacted considerable attention due to their special doping mechanism, high environmental stability, ease of processability and low cost, and the application in many fields.PANI has been obtained by chemical and electrochemical methods. However, it has many poor properites, for example, low molecular weight, poor solubility in common organic solvents and poor processing which limits their application. Two groups of the polymer have prepared and shown the special properties to enhance the electrical, chemical and physical properties such as copolymer, composite, dual-layerand mixture.Based on the above background, in order to improve the processability and stability of PANI, we chose aniline, aniline derivatives and oxides as the precursor to prepare the functional materials of polymer, copolymer and composite by using a simple method. Study the humidity sensing characteristics of these materials. We prepared the polymer films, copolymer films and polymer/inorganic composites by insitu polymerization on the slide on the gold-plated sensor electrodes.1. We prepared poly(o-phenylenediamine) based on self-assembled belt, board, block and strip nanostuctures by using a chemical oxidative polymerization of o-phenylenediamine (oPD) doped with hydrochloric acid, phosphatic acid, tartrate acid and sulfuric acid dopant on the lantern slide substrate. Study the humidity sensing characteristics of the materials doped with different acid. We found PoPD doped with phosphatic acid have the fast humidity and response reproducibility.2. We synthesis the oPD/An copolymer with the same method doped with phosphatic acid. Study the effect of the thermal stability, morphology and humidity sensing characteristics with the changing of the oPD/An molar ratios. We found that the copolymer has good thermal stability, conductivity and repose-recovery with the oPD/An molar ratios of 80:20. At the same time, we found that the copolymer has the fast sensitivity and reponse-recovery doped with D-camphor-10-sulfonic acid (CSA) dopant.3. We prepared m-phenylenediamine(mPD)/An copolymer by in-situ polymerization. By changing the molar ratios of reactants, reaction time, and concentration of hydrochloric acid, the morphology of nanoparitcles can be changed. We make a further humidity study on the copolymer.4. We synthesis the o-toluidine/An copolymer doped with hydrochloric acid. We found that the copolymer has good repose-recovery with the o-toluidine /An molar ratios of 1:1. This attribute to the interaction of copolymer and water molecules which may cause the electron charge delocalization along the polymer backbone.5. We prepare poly(o-toludine)/TiO2 composite doped with hydrochloric acid. We found that the increasing surface area as increased with the content of TiO2. This composite maybe used in the applications of sensors. The method of in-situ oxidative polymerization overcomes the shortcoming of the membrane by using traditional spin-coaitng.6. We study the mechanism of the PANI by using the FT-IR and Raman spectra with external voltage. Application of external voltage reduced the intensity in FTIR spectra and resulted in the shift of band situation.We concluded that external voltage could produce large average hopping energy, which allowed the charge transfer by hopping between the conducting domains during 0–75 V. The deprotonation of PANI was caused by Joule heating effect, resulting in the decreasing conductivity from 75 to 175V.