Preparation And Properties Of Aniline Derivatives Composite Electropolymerization Coatings

The corrosion of copper ions from copper-containing equipment poses a potential threat to biological systems.In this thesis,composite electropolymerization coatings of aniline and its derivatives were prepared by cyclic voltammetry（CV）on the surface of pure copper.The structural characterizations were featured by scanning electron microscope（SEM）,attenuated total reflectance infrared spectra（ATR-IR）,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.Besides,the anticorrosive performance of electropolymerized coatings were investigated for copper corrosion in corrosive medium through electrochemical measurements and spatial topography.Molecular dynamics（MD）simulation was introduced to study the morphology of polymers and the types and interaction energies of interactions with metallic copper substrates.The main research contents are as follows:（1）Nanostructured polyaniline（PANi）was electropolymerized on passivated copper surface via 20 CV in oxalic acid solution.Results of ATR-IR and XRD documented the occurrence of electropolymerization over copper surface.Electrochemical measurements showed that the corrosion current density i_corr（9.91μA/cm²）of the PANi electropolymerization coating was lower than that of bare copper（33.28μA/cm²）.Due to the obstruction of the PANi electropolymerization coating,the charge transfer process was blocked and the protection efficiencyη₂ value can reach79.90%,and its protection efficiency was significantly better than that of aniline（ANi）monomer adsorption coating.XPS analyses revealed that repeat units of polymer were in mixed state with predominantly oxidative type,which were inclined to parallelly deposit on copper surface with a strong anchoring strength.Molecular dynamics simulations well supported the configuration and forceful adhesion of polymers on Cu（1 1 1）plane.（2）Poly（N-methylaniline）（PNMA）and poly（N-ethylaniline）（PNEA）were electropolymerized on passivated copper surface via 20 CV in oxalic acid solution.SEM results showed that the average thickness of the PNMA and PNEA electropolymerized coatings was better than that of PANi electropolymerized coating.Electrochemical measurements showed that the i_corr values of the PNMA and PNEA electropolymerization coatings were 9.53 and 7.13μA/cm²,and the protection efficiencyη₂ were 80.10 and 85.10%,respectively.At the same time,the protection efficiency was significantly better than PANi.In addition,the protective effect of PNEA electropolymerization coating was slightly higher than that of PNMA.（3）Polyaniline molybdate-doped coating（PANi-Mo）and poly（N-ethylaniline）molybdate-doped coating（PNEA-Mo）were electropolymerized on passivated copper surface via 20 CV in oxalic acid solution.SEM results showed that the presence of molybdate increased the thickness of polymer coating.Electrochemical measurements showed that due to the cathode-induced dedoping and in-situ dissolution of molybdate,the i_corr values of the PANi-Mo and PNEA-Mo composite electropolymerization coatings were 3.55 and 2.75μA/cm²,respectively,and their protective effects were significantly better undoped.In equivalent monomers using dopants,the i_corr values were even higher than bare copper.Theη₂ value of the PNEA-Mo composite electropolymerization coating reached 93.46%.XPS analysis and MD simulation showd that the electropolymerized polymer is mainly composed of oxidized repeating units.The deposited polymer had a parallel configuration and forceful adhesion on Cu（1 1 1）plane,and the polymer and dopant had a favorable compatibility.（4）poly（N-ethylaniline）（PNEA）and its silicate-doped coating（PNEA-Si）,cinnamate-doped coating（PNEA-CA）,phosphate-doped coating（PNEA-P）were electropolymerized on passivated copper surface via 20 CV in H₂SO₄ solution.Different morphological features were obtained by SEM.The more regular the structure,the better the density of the electropolymerized coating.Potentiodynamic polarization showed that when immersed in 3.5%Na Cl solution for different periods of time,the i_corr value of the PNEA-CA composite electropolymerization coating reached the lowest value（0.42μA/cm²）after 48 h of immersion,and the protection effect was the best;The i_corr value of the PNEA-Si composite electropolymerization coating showed a trend of decreasing first and then increasing.When immersed for 96 h,it reached the lowest value（1.27μA/cm²）and the protection was higher than that of PNEA.The i_corr value of PNEA-P also showed a trend of decreasing first and then increasing,when immersed for 48 h,it reached the minimum value（0.59μA/cm²）.Electrochemical impedance spectroscopy can also verify the improvement of protection performance of different electropolymerization coatings.The protection effect of different electropolymer coatings followed the sequence of PNEA-CA>PNEA-Si>PNEA-P>PNEA.