The Synthesis Of Topological Ionic Polymers For Application To The Corrosion Inhibition On Metal

With the development of chemical industry,metal materials play vital roles in manufacturing and processing of the products.Copper and its alloys have been widely used in industry because of their excellent physical and chemical properties,such as excellent electrical conductivity,thermal conductivity,processability and corrosion resistance.However,copper and its alloys are vulnerable to corrosion damage in acid pickling solution or acid rain environment.Hence,these metal materials can be seriusly threatened by acid corrosion,and it may lead serious consequences.Therefore,it is of great significance to prevent the corrosion of copper in acid medium effectively,which is related to the national economy,people’s livelihood and sustainable development.Ionic polymers are widely used in many fields due to their good amphiphilicity,self-assembly,thermal stability and so on.Thus,a series of ionic polymers（IPs）with topological structure were designed and synthesized in this paper.Based on the self-assembly properties of IPs,the corrosion inhibition properties of target ionic-type polymer aggregates are investigated,which reveals the relationship between chemical structure and corrosion inhibition properties of the target polymers.The mainly research work and corresponding results of this thesis are highlighted as following:（1）The new linear ionic liquid copolymers IP1 and IP2,which were based on alkyl chain linked bis-imidazole monomer,were designed and synthesized,and their aggregation behaviors in 0.5 M H₂SO₄ solution were studied.The results show that IP1and IP2 can form regular aggregates in sulfuric acid solution.The chemisorption mechanism of IP1 and IP2 aggregates on copper surface was revealed by Fourier transform infrared（FT-IR）,Raman spectroscopy,X-ray photoelectron spectroscopy（XPS）.The results of electrochemical test indicate that the studied IP1 and IP2aggregates could simultaneously restrain the anodic and cathodic corrosion reaction process of copper in sulfuric acid solution,and the inhibition effect on the cathodic corrosion reaction is more significant.The adsorption behavior of IP1 and IP2aggregates on the metal surface follows the Langmuir isothermal adsorption model.The thermodynamic parameters obtained by fitting the adsorption isotherms curves as well as the results based on the density functional theory（DFT）reveal the adsorption and anti-corrosion mechanisms at the molecular level.（2）The novel linear solid-liquid ionic polymers IP3 and IP4 were prepared,which can process self-assembly in 0.5 M sulfuric acid aqueous solution.It is discovered that the size and morphology of the resulted aggregates are shown dependence on aggregation concentration and aggregation time.The chemical chelation interaction between the aggregates and copper substrates was studied by FT-IR,Raman and XPS spectra.Furthermore,the characterization of polarization curves at various temperatures indicate the presence of physical adsorption behavior during the adsorption process of the IP3 aggregates and IP4 aggregates on metal surface.The electrochemical characterizations show that the protection layer of IP3 aggregates and IP4 aggregates formed on copper electrode possess good corrosion resistance property in aggressive acid medium.The quantum chemical calculation further implies that the imidazole ring is the mainly active site for chemical chelation interaction with the copper surface,Furthermore,the nitrogen atom with the most electronegativity has the strongest reactivity with cuprous ions.The molecular dynamics simulation（MD）results reveal that the parallel adsorption configuration of IP3 and IP4 aggregates on copper surfaces can form the maximal surface coverage,and the adsorption capacity of IP3 and IP4aggregates on metal surfaces is quantified by the calculated E_binding values.（3）Based on the molecular preconstruction,the novel synthesized"A2/A3+B3"topological hyperbranched solid-state ionic polymer aggregates were used to achieve effectively corrosion resistance for copper in sulfuric acid solution.The results imply that the as-prepared two topological hyperbranched solid-state ionic polymers with different degrees of branching（IP5 and IP6）can form the regular aggregates in mixed ethanol/0.5 M H₂SO₄ aqueous solution.In addition,the morphology and size of the obtained aggregates are closely related to the aggregation concentration and aggregation time.The metal surface study shows that the protective IP5 and IP6 aggregates film formed on the copper surface is mainly due to the Cu（I）-N chelating bond.Furthermore,the physical adsorption was confirmed by polarization curve tests at different temperatures,which could ensure the growth and stability of protective aggregates layer.The electrochemical results indicate that the protective aggregates film formed on the copper surface shows good corrosion resistance capability in strongly aggressive sulfuric acid aqueous solution.Moreover,the local distribution of electron density and Mulliken charge in the HOMOs and LUMOs orbitals.In addition,the MD simulation results imply that the nitrogen atoms in the imidazole ring play an important role in the chemisorption process.（4）The“A2+B3”topological hyperbranched ionic liquid type polymers were designed and synthesized,and their self-assembly behavior in mixed ethanol/0.5 M H₂SO₄ aqueous solution was investigated.The inhibition ability and mechanism of the above ionic liquid polymers（IP7,IP8 and IP9）aggregates on copper corrosion in dilute sulfuric acid aqueous solution were studied.The results of metal surface analysis indicate that IP7,IP8 and IP9 aggregates can form thick adsorption films on copper substrates by chemical complexation,and the adsorption process obeys the Langmuir adsorption isothermal model.The polarization curves and electrochemical impedance spectroscopy imply that the corrosion inhibition efficiency of the above ionic liquid polymer aggregates increases with the increase of alkyl chain length in the repeating unit structure.The DFT quantum chemical calculation results show that the energy gap values of repeating units of the three ionic liquid polymers conform the following order:IP7>IP8>IP9,indicates that IP9 containing the longer alkyl chains exhibits the stronger corrosion inhibition effect.This conclusion is consistent with the results of electrochemical test.Mulliken charge distribution further reveals that the nitrogen atoms in the imidazole ring of the three polymers have a stronger electron-donating capability.Beaises,the binding energy between the repeating units and copper substrate obtained by MD calculation also increases with the increase of the chain length,which further interpret the experimental results well.（5）The"A2/A3+B4"topological hyperbranched solid-liquid ionic polymer IP10,IP11 and IP12 are designed and synthesized.It is demonstrated that these ionic polymers can form regular nano-to micro-meter J-type aggregates in ethanol-sulfuric acid mixed solution.The results of the copper surface test indicate that the IP10,IP11and IP12 aggregates can chelate with Cu（I）through the nitrogen atoms in the imidazole ring to form the dense protective film on the metal surface,and these adsorption films possess good corrosion resistance capability in sulfuric acid aqueous solution.The quantum chemical calculations further demonstrate the key roles of nitrogen atoms in the chemical adsorption process.The electrochemical test reveals that the above three ionic polymer aggregates can efficiently inhibit the cathodic and anodic reactions at the same time,and decrease the cathodic corrosion reaction rate more greatly.In addition,the adsorption of IP10,IP11 and IP12 aggregates on copper surface follow the similar inhibition mechanism on copper corrosion.The MD simulation results reveal the parallel adsorption configurations of the target aggregates on the metal copper surface,and the order of calculated binding energy values is IP10 aggregates<IP11aggregates<IP12 aggregates,which is positive correlation with the corrosion inhibition efficiency obtained by electrochemical tests,indicating that the IP12 aggregates with the higher branching degree of molecular skeleton presents the stronger corrosion inhibition ability on copper corrosion.