Preparation And Electrochemical Behavior Of Conducting Polymers

Conducting polymer such as poly(o-pheyIenediamine)(PPD) has attracted considerable attention because of its applications in electrochemical diode, chemical sensor, permselectivity for a dissolved species, electrocatalysis, etc. Ionic liquids are environmentally benign and widely used in catalysis, synthesis and electrochemistry. In this dissertation, we studied the electropolymerization of o-phenylenediamine by using ionic liquid [EMIM]Br, [HMIMJBF4 as solvent and supporting electrolyte.We researched the electropolymerization of o-phenylenediamine in ionic liquid [EMIMJBr by cyclic voltammetry, constant potential and galvanostat method. It could't get the polymer film when the monomer concentration was lower than 0.01M. When the scan range was -l.2V~-t-0.2V, or the constant potential was lower than 0.2V, the polymer film was not produced. So scan and constant potential should be higher than the oxidation potential of the monomer. The PPD films were got at the galvanostat density 3mA/cm2~ 10mA/cm2. The prepared PPD films had perfect electrochemical activity in the HaSO4 solution, which the range of pH value was 1~ 4.We discussed the charge transport within the PPD films and estimated the charge diffusion coefficients by the potential-step technology-chronoamperometry and chronocoulometry. The polymer films showed the permselectivity for a dissolved species ion. The PPD films prepared in ionic liquid was permeable to catechol, and the reversible vollammetric wave of catechol was observed. However, the PPD film prepared in acidic solution could penetrated catechol, in which reaction of catechol is irreversible. So the PPD films prepared in ionic liquid had preferable stability.The IR absorption spectra of PPD was observed at 830~840cm-1, which was assigned to the skeletal vibrations of the phenazine ring. The UV-vis absorption spectra( max) of PPD was at 430nm in dimethyl sulfoxide. Through the analysis of thermogravimetry and derivative thermogravimetry of PPD, the PPD powders char yield at 850 C, which exhibited perfectly stability.Compared to electropolymerization of o-phenylenediamine in acidic solution, the oxidation potential of the monomer was reduced by 0.629V and 0.426V in ionic liquids [EMIMJBr and [HMIMJBF4, respectively. So the monomer was oxidized easily, avoiding peroxidization of the polymer. We discussed various factors about the electropolymerization of o-phenylenediamine in ionic liquid [HMIM]BF4, such as concentration, temperature, scan rate, and scan times. It was founded that the PPD films had perfect electrochemical activity in pure ionic liquids [HMIM]BF4. We studied the preparation of electrocatalytic performance of nanocrystalline TiO2 film electrode and electropolymerization of aniline.