Study On Electrosynthesis, Electrochromic Behavier Of Couducting Copolymers Based On Poly(O-anisidine)

Poly(o-anisidine),as a hopeful conducting polymers,have attracted considerable attention due to its relatively easy preparation,low-cost,excellent environmental stability,good electric conductivity and its wide range of potential applications, including presently fields such as sensors, electrochromic and photovoltaic devices,supercapacitors, and so on. Especially in the aspect of electrochromic materials, it shows attractive electrochromic properties, such as fast response time, high coloration efficiency and contrast ratio, good stability, and wide range of colors. Poly(o-anisidine), copolymers of o-anisidine and o-chloroaniline,copolymers of o-anisidine and anthranilic acid, copolymers of o-anisidine and o-chloroaniline in the presence of SDS, copolymers of o-anisidine and anthranilic acid in the presence of SDS, terpolymers of o-anisidine, anthranilic acid and aniline,respectively, were prepared by potentiostatic method in aqueous acidic solution of 0.5mol/L H2SO4. The resulting homopolymers/copolymers were washed with deionized water and subsequently characterized in situ UV-vis spectroelectrochemical, SEM, FTIR and so on. The electrochromic behaviors of the polymer films were stuied in detail. Experimental results showed that polymers could be improved by adjusting the parameters of the polymerization process (polymerization potential, monomer concentration), copolymerization, and changing the reaction medium. (1) The structure, surface morphology, electrical conductivity, electrochemical activity and electrochromic behavior of poly(o-anisidine) prepared by constant potential electrolysis were closely linked with electrode potential.Poly (o-anisidine) films were electrochemically synthesized on Pt electrode at different electrode potential(650mV,750mV and 800mV) and investigated by cyclic voltammetry, electrochemical impedance spectroscopy, SEM, Raman spectroscopy and XRD.The results showed that the surface morphology of PtPOA750 prepared at 750mV was more rough and grainy.At the same time,it had poor conductivity.Poly(o-anisidine) deposited on ITO conductive glass had good electrochromic properties, which POA650 prepared at 650mV possess the fastest electrochromic rate.It was related to the order chain of POA650 surface morphology.The result of XRD showed that POA650 polymer had a larger lattice spacing, further confirmed that the ordered crystal structure of the polymer film was more conducive to the ion exchange in redox process. (2) Two series of copolymers, one of o-anisidine with o-chloroaniline and the other of o-anisidine with anthranilic, have been synthesized by electrochemical polymerization on ITO electrode.The copolymerization of o-anisidine with o-chloroaniline was carried out using a constant concentration of o-anisidine (20mM) and different o-chloroaniline concentrations (20mM - 100mM) in the feed. The presence of o-chloroaniline was not only accelerated polymerization but also promoted polymerization.The electrochromic reversibility of copolymers was improved significantly, the electrochromic properties of CP2080 copolymer is the best, which was obtained by the constant potential electro-polymerization of solution containing 20mM o-anisidine and 80mM o-chloroaniline.The copolymerization of o-anisidine with anthranilic acid was carried out with different feed concentrations of anthranilic acid (20mM-100mM) and a constant concentration of o-anisidine (20mM). The copolymer CPA2080, prepared from the solution containing 20 mM of o-anisidine and 80 mM of anthranilic acid, had the best electrochromism performance, and was better than CP2080 copolymer. The reason is that aniline derivatives with acidic side groups,-COOH, are of particular interest as the -COOH can also act as internal proton-doping agents, which formed self-doped polymers. At the same time, opolymers of o-anisidine and anthranilic acid were more stable under high potential, which is caused by the strong electrostatic interaction between the -COO- groups and nitrogen atom of the cationic group. (3) Study on the influence of surfactant SDS in the polymerization process of the monomers and evaluate the properties and structure of the polymers formed in presence of SDS.In the presence of SDS, poly(o-anisidine), poly(o-chloroaniline), poly(anthanilic) poly(o-anisidine-co-o-chloroaniline), poly(o-anisidine-co-anthranilic acid) were prepared by potentiostatic method in aqueous acidic solution of 0.5mol/L H2SO4. By adding SDS anionic surfactant to the monomer solution, the rate of polymerization increased considerably and the monomer oxidation potential lowered significantly. The films electrodeposited in the presence of SDS were more rough, more stable, better electrochromism and not easy degradation under high potential than those deposited in the absence of SDS. So the surfactants also could improve physical and mechanical properties of the polymers and produce adherent and well-organized films on the electrode surface. (4) In this study, ter-polymer films of o-anisidine, anthranilic acid and aniline have been electrochemically synthesized on ITO electrode.The resulting ter-polymer films were characterized with in situ UV-Vis Spetroelectrochemistry and scanning electron microscopy (SEM). It was observed that the adding aniline to the soulution of o-anisidine and anthranilic acid could accelerate polymerization. The synthesized ter-polymer films were completely different in aspect of morphology, stability and structural properties when compared to single polyaniline film. The results showed that there was an optimum concentration of aniline in trimerization system making ter-polymer film with better electrochromism performance.