Effect of attached peroxyacid on liquid phase depositional polymerization of EDOT over PI film with adsorbed ferric chloride

To synthesize conducting PEDOT coating on polyimide (PI), hydrolyzed PI film was immersed in H2O2, FeCl3, and EDOT solutions sequentially. The surface compositions of PI after H2O2 immersion were analyzed with XPS and the content of introduced peroxide was determined by iodometry. The content of FeCl3 adsorbed on PI was evaluated by ash method. The effect of the peroxide and FeCl3 oxidants on the formation of PEDOT coating and the conductivity of the resultant PEDOT/PI were investigated. In H2O2 solution, carboxylic groups on hydrolyzed PI transformed to peroxyacid groups at magnitude of mmol/m2. H2O2 concentration promoted the formation of peroxyacid but depressed the adsorption of FeCl3. Attached peroxyacid alone could not initiate the oxidative polymerization of EDOT but could work as secondary oxidant with FeCl3 together. It enhanced the oxidizing capacity of adsorbed FeCl3 and led to more conducting PEDOT coating. The sheet resistance of PI film could decrease eight orders of magnitude to 400 Ω/□ after oxidative polymerization in EDOT solution. Without H2O2 treatment, the sheet resistance could be reduced to several kΩ/□ only. The attached peroxyacid enhanced the efficiency of adsorbed FeCl3 to the formation of conducting PEDOT coating greatly.