Study On Electro Polymerization Of Aniline On Steel And Effect Of Titania On The Polymerization

In-situ reflecting ellipsometry and cyclic voltammetry have been used to study the electro polymerization of aniline on steel electrode in sulfuric acid electrolytes containing TiO2 and only sulfuric acid electrolytes. The influence of scan rate, scan potential ranges on the growth and performance of polyaniline film has been analyzed. The mechanism of aniline polymerization in two different electrolytes has been investigated. The results indicate that aniline free radicals produce and begin to polymerize at scan potential of 0.6V(vs.SCE) and polymerize promptly at 0.75V(vs.SCE) upwards. Besides, The results also indicate that polymerization rate increases rapidly when there is little polyaniline on the electrode. All these show that aniline polymerizes in a mean of catalyzing itself. An increase earlier and a decrease again in the ellipsometric spectroscopy parameter prove that growth and dissolution exist alternately in the growth of film. That Cyclic voltammograms for the electro-deposition of PAn are similar in shape to each other in the two different sulfuric acid electrolytes indicates that the principle of aniline polymerization is not affected by the presence of titania.The X-ray diffraction (XRD) and differential scanning caloricity (DSC) experiments have been used to study the ingredient of PAn film and PAn-TiO2 composite film. The results reveal that polyaniline as-electrodeposited is uncrystallized. The courses of implanting TiO2 and formulating N-Ti band go with polymerization of aniline when depositing polyaniline film from sulfuric acid electrolytes containing TiO2 and TiO2 exsists in as-deposited polyaniline film. The N-Ti band is explained in term of the formation of the band between Ti having empty orbits and N having solitary pair electrons. The resistance of various films is measured by "layer cell" designed to study the influence of TiO2 on electrical performance of polyaniline films. It is founded that the incorporation of TiO2 enhances conducting performance of polyaniline films. The reason is analyzed and conducting mechanism of composite film is discussed. The particular effects of nano-TiO2 enhancing doping efficiency of polyaniline make electrical conductivity increase. Conducting mechanism of composite film remains dependent on energy band theory for semiconductor and limit region state theory for polymers. The solubility of polyaniline film is also discussed. Polyaniline film can be dissolved by thick HNO3(75%) and HNO3(40%)+H3PO4(40%)but not by dilute HNO3 and H3PO4. The former is attributed to the same nitration reaction between polyaniline and thick HNO3 as between aniline and thick HNO3.