Orderly self-assembly of new ionic copolymers for efficiently protecting copper in aggressive sulfuric acid solution

Journal Pre-proofs Orderly self-assembly of new ionic copolymers for efficiently protecting copper in aggressive sulfuric acid solution Haijun Huang, Yan Fu, Fuhua Li, Zhenqiang Wang, Shengtao Zhang, Xinchao Wang, Zhiyong Wang, Hongru Li, Fang Gao PII: DOI: Reference:

S1385-8947(19)32705-6 https://doi.org/10.1016/j.cej.2019.123293 CEJ 123293

To appear in:

Chemical Engineering Journal

Received Date: Revised Date: Accepted Date:

2 June 2019 24 August 2019 25 October 2019

Please cite this article as: H. Huang, Y. Fu, F. Li, Z. Wang, S. Zhang, X. Wang, Z. Wang, H. Li, F. Gao, Orderly self-assembly of new ionic copolymers for efficiently protecting copper in aggressive sulfuric acid solution, Chemical Engineering Journal (2019), doi: https://doi.org/10.1016/j.cej.2019.123293

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Orderly self-assembly of new ionic copolymers for efficiently protecting copper in aggressive sulfuric acid solution Haijun Huang1, Yan Fu1, Fuhua Li1, Zhenqiang Wang1, Shengtao Zhang1*, Xinchao Wang1, 2*, Zhiyong Wang1*, Hongru Li1*, Fang Gao1*

1College

of Chemistry and Chemical Engineering, Chongqing University, Chongqing, China, 400044

2College

of Pharmacy, Heze University, Heze, Shandong Province, China, 274000

Tel: 86-23-65102531, Emails, [email protected]; [email protected]; [email protected]; [email protected];

[email protected]

Abstract In this study, new ionic polymers (IPs) based on the copolymerization of rigid aromatic phenylmethyl-linked bisimidazole and dibromide derivatives are presented. The prepared IPs display orderly self-assembly in 0.5 mol/L aqueous sulfuric acid solution. Furthermore, the formed IPs aggregates with regular elliptic or circular-like shape exhibit the strong adsorption capability on the studied copper surface in aggressive acid medium, which occurs mainly via the chemical chelation bonding with cuprous ions demonstrated by the FT-IR spectroscopy, Raman spectroscopy together with XPS spectroscopy. In addition, the polarization tests at the different temperatures indicate the physisorption of the IPs aggregates on Cu surface can be presence. The electrochemical measurements show that the formed robust IPs-assemblies layers can protect the studied copper specimens efficiently with the maximal corrosion inhibition efficiency of 97.8% (IP1) and 96.8% (IP2) in aqueous sulfuric acid solution. The results are further understood by the molecular modeling and molecule dynamic simulation, and the electronic density distribution of the surveyed IPs and the optimal equilibrium configurations on Cu slab are revealed and analyzed. The results presented in this study could act as the models for guiding us to develop new organic corrosion inhibitors for metal in aggressive media.

Keywords: Self-assembly; Ionic copolymer; Copper; Corrosion inhibition; Sulfuric acid solution 1. Introduction 1

With the development of modern industry, metal materials play crucial roles in manufacturing and processing of the products. Copper and its alloys are extensively employed in industry due to the extraordinary physical and chemical natures, such as excellent electrical, thermal conductibility and fine machinability as well as neat corrosion resistance [1-5]. It is accepted that the oxidation films of Cu2O and CuO can be formed on copper surface, which may decrease the corrosion process of the metal. On the other hand, the covered copper oxides film may perform quite inferior electrical and thermal conductivity in the chemical and microelectronic industrial production. Thus, aqueous sulfuric acid solution is often employed to remove the metal oxides film from the copper surface. Unfortunately, the metal surface can be destroyed by the aggressive acid ions [6, 7]. Besides, copper and its alloys are easily attacked by acid rain that often happens due to the excess emission of NOx and SOx yielded by the large coral and oil consuming. Hence, it is a significant challenge to develop highly efficient inhibition methods for copper in aqueous sulfuric acid medium. Some organic molecules including the hetero-atoms (such as nitrogen, oxygen, sulfur, phosphorus etc.) may show strong inhibition corrosion nature, because they are capable of forming protective films through the chemical coordination bonding with metal ions [8-12]. This means that the adsorbed films on copper may be determined by chemical chelating between organic inhibitor molecules and copper ions. Therefore, it is significant to improve the protective films covered on metal surface by strengthening the chemical interactions of organic inhibiting molecules with metal ions. Ionic polymers (IPs) that are composed of cations and counter anions are characterized with various advantageous properties such as ions conductivities [13, 14], ions exchange properties 2

[15], nonflammability [16]. In particular, good amphiphilic nature of IPs receives more considerable interests [17-19] due to the self-assembly [20] and surface activity [21] in aqueous solutions without any organic solvents. Thus, IPs are found in a variety of applications including corrosion inhibition [22], electronic devices [23, 24], electrochemical sensors [25, 26], electrolytes for batteries [27], membranes for fuel cells [28], polymer actuators [29], and even antimicrobial materials [30]. Our previous work investigated the self-aggregation behavior and anti-corrosion performance of soft alkyl chain linked bisimidazolium (1,4-di(1H-imidazol-1-yl)butane, DIB) based polymer ionic liquids (PILs), which could produce assembled PILs aggregates for notable corrosion inhibition to copper in sulfuric acid aqueous solution [31]. In this study, we propose to employ the aromatic rigid phenmethyl as the linker to construct the starting monomer, which offers more phenyl rings and greater amphiphilicity. Hence, the aromatic rigid linker-included bisimidazolium based ionic polymers (IPs) could display more regular self-aggregation in aqueous aggressive acid solutions. Therefore, the target self-assembly of new ionic copolymers contains more aromatic rings, which favors the chemical adsorption of the acquired IPs assembly on the metal surface. As a consequence, the IPs aggregates contain thousands of heterocyclic functional groups and aromatic rings that can chelate with metal ions, and thus the yielded organic aggregates protective layer adsorbed on the metal surface can efficiently restrain the corrosion in aqueous acid solutions. Therefore, the current work presents the synthesis of the target IPs based on the copolymerization of aromatic rigid phenylmethyl-linked bisimidazole and dibromide derivatives (Scheme 1). The prepared target IPs may produce the orderly aggregates in aggressive H2SO4 aqueous solution, which inspires strengthening the chemical coordination with metal ions. The 3

acquired IPs aggregates are characterized by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS) as well as zeta potential. In addition, the Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) are performed to farther investigate the chemisorption of the target IPs aggregates on the surveyed Cu sample surfaces.

Br Br DBMB

N DMF/Methanol 110 0C, one week

N

Br-

N

NBS/BPO CCl4

Methanol

Br Br

N

N

N Br -

IP1

n

N

NH N

N

DIMB DMF/Methanol 130 0 C, one week

Br

Br

N

N

Br -

IP2

N

N Br-

n

DBT

Scheme 1. Chemical structures and synthesis routes of the target IPs.

The current work further studies the anti-corrosion nature of the investigated IPs aggregates in 0.5 mol/L (M) H2SO4 solution via different means including the polarization curves, the electrochemical impendence spectroscopy (EIS) and the atomic force microscopy (AFM). The interaction mechanism between the surveyed IPs aggregates and the Cu specimen surfaces is understood by the Langmuir isotherm plot, molecular modeling as well as the molecular dynamic simulation.

2. Experimental procedures 2.1. Materials and characterizations The IPs (IP1, 2) were synthesized according to Scheme 1. The initial materials were supplied by the Sigma-Aldrich Chemical Corporation. The analytical grade organic solvents in this study were provided by Acros Chemical Corporation. The detail synthesis description was 4

given in “Supplementary Materials”. The Bruker nuclear magnetic resonance (NMR) apparatus (600 MHz) was employed to identify the chemical structures of monomers and target IPs at room temperature (298 K), the chemical shifts of 1H or 13C NMR peaks were referenced to those of tetramethylsilane (TMS). The FT-IR spectroscopy of the samples was obtained by Thermo Scientific apparatus of Nicolet iS50 Fourier transform infrared spectrometer. The differential scanning calorimetry (DSC) 204F1 apparatus was used to survey the thermal properties of the target IPs in the range of 5-300 °C at a 10 °C min−1 heating rate in N2 atmosphere. A Waters Gel Permeation Chromatography (GPC) (HLC-8320 GPC) system was used to determine the molecular weights of the surveyed IPs. The CE440 elemental analysis meter was used to obtain the elemental information of the monomers. The refined Cu (99.99 wt%) was utilized as the working electrode (WE) in the electrochemical experiments. The copper samples were processed into cylinder with a diameter of 1 cm and a thickness of 0.2 cm before the electrochemical determination. The most part of the metal sample was covered with epoxy resin, and 0.25π cm2 area part directly contacted with air or acid aggressive media. The Cu samples were polished successively by SiC waterproof abrasive with different meshes including 400, 800, 1200, 2000, 3000, 5000 grits prior to the measurements. The polished copper samples were ultrasonically washed and dried for the experimental surveys. 2.2. Self-assembly of the target IPs and formation of the IPs aggregates protective layers on copper substrate The self-assembly processes of the studied IPs aggregates and the following measurements were presented in Figure 1. The studied IPs aggregates with the concentrations of 0.025-0.300 5

g/L were prepared in aqueous sulfuric acid solution, and the self-assembly was performed at room temperature.

Figure 1. A diagram of the surveyed IPs aggregation formation process and the following experiments.

The morphologies and sizes of the studied IPs aggregates were identified by the SEM (Jeol-JSM-3.5 CF, Japan) and TEM (JEM 1200EX, Japan), which used 5.0 kV and 120 kV as the acceleration voltages, respectively. The gained IPs aggregates dispersed in aqueous sulfuric acid solution was slightly titrated on the surface of a silicon plate by using a micro-syringe, which was then dried under vacuum to prepare the SEM and TEM samples. The tiny amount of gold powder was sputtered on the sample surfaces for enhancing the electronic conductivity of organic species. The crystalline states of the investigated IPs aggregates were determined by X-ray diffraction (XRD). A Perkin Elmer (PE) amorphous silicon detector was employed to measure the XRD patterns of the samples. The preparation of the XRD samples was similar to that of the SEM samples. The dynamic light scattering (DLS) surveys were employed to investigate the IPs aggregates by Malvern nano-zetasizer (Malvern Instrument, UK). Besides, the zeta potential was detected via Zetasizer (Nano-ZS, Malvern Instrument, UK) to 6

determine the stable aggregation state of the acquired IPs aggregates with Dispersion Technology Software (DTS). The ultraviolet/visible absorption spectra of the IPs aqueous acid solution at different aggregation time were performed by a TU1901 spectrophotometer of Beijing PUXI General Equipment Limited Corporation. The freshly polished copper samples were ultrasonically processed by 7 M hydrogen nitrate solution for 10 s, then washed with deionized water and absolute ethanol sequently and promptly. Thus, the clean and oxide-free metal samples were obtained, which was then transferred rapidly into the aqueous sulfuric acid solution including the stable IPs aggregates for 2 h (it has been shown that the stable adsorbed protective film was formed on the metal surface accompanying with the steady electrochemical performance acquired via 2 h immersion time). After that, the modified copper specimens were cleaned by pure ethanol and dried in vacuum for the following detection. 2.3. Copper surface determination The FT-IR spectroscopy of the investigated IPs and IPs-aggregates was performed ex-situ, employing Nicolet iS50 (Thermal Fisher, USA) in the range of 500-4000 cm-1. The Raman spectroscopy of Cu substrates which were covered by the IPs-aggregates was obtained through a Raman spectrometer (Renishaw, UK). The Raman shift was calibrated by silicon at 519 cm-1. The XPS spectra of the metal samples were collected in a K-Alpha XPS apparatus (Thermal Fisher, USA) at the room temperature. The binding energy scales were adjusted by the C 1s peak of the aliphatic carbon contamination at 284.8 eV. The XPS spectra of the samples were de-convoluted and analyzed by the XPS peak software with the Shirley-type background. The SEM (Jeol-JSM-3.5 CF, Japan) at 5.0 kV and the AFM (MFP-3D-BIO, Asylum Research, 7

America) were carried out to study the morphologies of the uncovered copper samples, and IPs aggregates covered Cu surfaces. 2.4. Electrochemical characterizations The routine three-electrode cell was employed in the electrochemical characterization, including the potentiodynamic polarization curves (Tafel curves) and electrochemical impedance spectroscopy (EIS) at 298 K. In addition, the Tafel curves were also detected at 308 K, 318 K, 328 K and 338 K, respectively, to investigate the effect of corrosion temperatures, and the kinetic parameters on the corrosion process were obtained. The prepared Cu specimen was used as WE, and the saturated calomel electrode (SCE) equipped in a Luggin Capillary was employed as the reference electrode (RE), and a platinum foil (area, 2.0 × 2.0 cm2) acted as the counter electrode (CE). It is noted that all the potential values in the current work were measured relative to ESCE. The electrochemical determination was conducted by the CHI660C electrochemical working station (Shanghai Chenhua, China). The steady values of open-circuit potentials (OCPs) for WEs were obtained within 30 min, which was presented in Figure S1. The Tafel curves were detected in the potential range of ± 250 mV versus the OCPs with a scanning speed of 1 mV s-1. The EIS were surveyed in the frequency range of 100 kHz to 0.01 Hz at the steady-state of the OCPs, and the amplitude of the alternating voltage used in the EIS determination was 5 mV. The corrosion rate (CR) in milli-inches per year (mpy) could be calculated from the detected value of corrosion current density by Eq. (1) [32]: CR  0.13 jcorr EW / d

(1)

wherein jcorr was the corrosion current densities (μA•cm-2), EW represented the equivalent weight of copper and d showed the density. 8

The corrosion inhibition efficiency (η) of the studied IPs-aggregates was obtained by the following equations [1, 33]:

η j = (1 ηE 

jcorr jcorr,0

)  100%

R ct  R ct,0 R ct

 100%

(2) (3)

wherein, jcorr,0 and jcorr were the corrosion current densities of the unmodified and modified WEs by the investigated IPs aggregates, respectively; and Rct,0 and Rct showed the charge transfer resistances without and with the investigated IPs-aggregates, respectively. 2.5. Molecular modeling and molecular dynamic (MD) simulation details The density functional theory (DFT) was adopted to perform the molecular modeling by Gaussian 09 program package [34]. The representative IPs repeating units were used in the geometry optimization at DFT level using B3LYP methods under the basis set of 6-311++G (d, p), and water was employed as the solvent in the molecular modeling process [35, 36]. In addition, the calculated results containing the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO) and the energy gap ΔE (ΔE= ELUMO EHOMO) were analyzed. To investigate the interaction mechanism of the IPs aggregates with copper surface in the presence of aggressive acid aqueous solution, the molecular dynamic (MD) simulation was carried out by Materials Studio (MS) 5.5 software [37]. The cleaved Cu(1 1 1) surface from pure copper crystal was employed as the representative owning to its most steady structure with low Miller indices [38]. Followed by the geometry optimization under molecular mechanics, the Cu (1 1 1) was enlarged to 10 × 10, and all the four layers of copper atoms are fixed subsequently. The simulation box included a Cu slab, an aqueous phase (consists of 300 H2O, 1 IP repeating unit, 3 9

H2O+ and 3 HSO4-) and a vacuum layer with height of 30 Å. Thus, the approximately real state simulation of the IPs aggregates interacting with the Cu surface in 0.5 M H2SO4 aqueous solution could be achieved. The COMPASS force field with periodic boundary conditions was employed to carry out the simulation box. The simulation temperature was set at 298 K which controlled by Anderson thermostat, NVT canonical ensemble, a time step of 1.0 fs and total simulation time of 3000 ps were assigned in MD simulations, respectively [39, 40]. In addition, the interaction strength between the inhibitor molecule and Cu surface can investigate quantitatively using the values of the adsorption energy (Eadsorption) and binding energy (Ebinding) which can be calculated by Eqs. (4) and (5) [41, 42]: Eadsorption= Etotal - (Esurface+solution + Einhibitor+solution) + Esolution (4) Ebinding= -Eadsorption (5) wherein Etotal was the total energy of the simulation box, Esurface+solution represented the total energy of the system without any inhibitor molecule, Einhibitor+solution showed the total energy of the system without the copper slab, and Esolution was the energy of the aggressive medium solution [43]. 3. Results and discussion 3.1. Synthesis and characterization of the target IPs The copolymerization of aromatic rigid phenylmethyl-linked bisimidazole and dibromide derivatives was conducted in a long reaction process (one week) to yield the great weight-average molecular mass of the target IPs, which are in the values at approximate 14000. The DSC curves (Figure S2) reveal that the studied IPs do not exhibit the dramatic endothermic peaks, suggesting the thermal-stable nature of the IPs. Figure 2 presents the 1H-NMR spectra of the prepared IPs. It is shown that the 1H-NMR 10

peak of H(a) of IP1 is located in a quite lower magnetic field, which is due to the electron-accepting effect of Br- (Figure 2a). The 1H-NMR peaks assigned to H(b, c) of the target IP1 display the close chemical shifts of 7.638 and 7.592 ppm because of the similar chemical environments. The remaining 1H-NMR peaks of the studied IP1 can be easily identified. The similar 1H-NMR spectral phenomena of the target IP2 are discovered in Figure 2b.

Figure 2. 1H-NMR spectra of the target IP1 and IP2.

3.2. Formation of the studied IPs aggregates in aqueous H2SO4 solution Figure 3 presents the variations of the formed IP1 aggregates with increasing the assembly evolving time in sulfuric acid aqueous solution at 0.200 g/L. It is shown the sizes of the IP1 aggregates increase from approximate 300 nm (30 min) to 2.5 μm (4 h). However, as the assembly time further increases at 8 h, the sizes of the IP1 aggregates do not show the great changes. The results indicate that the aggregation of the IP1 achieves a stable state at 4 h self-assembly time. In addition, the IP1 aggregates show elliptic or circular-like particles at various aggregation time. Furthermore, the TEM imaging results also show the elliptic or circular-like shape of the acquired IP1 aggregates obtained at 2 h self-organization time (Figure S3a). The inner structure could not be recognized by the TEM image due to the too thick aggregates [44].

11

Figure 3. SEM images of the IP1 aggregates in 0.5 M H2SO4 solution at various aggregation time, 30 min (a), 2 h (b), 4 h (c) and 8 h (d), 0.200 g/L.

The DLS determination shows that the size distribution of the aggregates is concentrated in about 300 nm after 30 min self-assembly time. While the assembly time increases to 4 h, the average size value increases to approximately 2.5 μm (Figure S4a), and the homologous zeta potential reaches -46.0 mV (Figure S5a), which implies that a stable assembly state is achieved [45]. Figure 4 further shows that the IP1 aggregates present the size increases with the increasing concentrations of IP1 from 0.025 g/L (400 nm) to 0.200 g/L (2.5 μm). On the other hand, no orderly aggregates are formed at 0.300 g/L. It indicates that the IP1 aggregates reach the peak size values at 0.200 g/L with 4 h assembly evolving time. The results show that the shapes and sizes of the produced IPs aggregates are shown the dependence on the concentrations of the IPs in aqueous acid solution. This can be further demonstrated by the DLS determination. The similar self-assembly phenomena of the IP2 are presented in Figure S6 and Figure S7. 12

Figure 4. SEM images of the studied IP1 aggregates at various concentrations in 0.5 M aqueous H2SO4 solution at 4 h, (a) 0.025 g/L, (b) 0.050 g/L, (c) 0.100 g/L, (d) 0.200 g/L and (e) 0.300 g/L.

The crystalline states of the studied IPs aggregates at the different aggregation concentrations and the assembly evolving time are discovered by the determined XRD patterns (Figures S8a (IP1) and S8b (IP2)). The results imply that the presence of crystalline and harmonious arrangement of the target IPs. Furthermore, the crystalline states of the surveyed IPs aggregates show the close relationship with the assembly concentrations and time. In addition, the UV/visible absorption spectroscopy of the studied IP1 aggregates (Figure S9a) and IP2 aggregates (Figure S9b) present the red-shift of the peak wavelength as well as the formation of a new level-off absorption tail at the stable assembly state (4 h), which reflects the occurrence of J-type aggregation of the IPs in aqueous acid solution [46, 47]. It is understood that π-π interactions between the imidazolium rings as well as the attendant formation of an H-bonded network involving hydrogen ions, counter anions, imidazolium cations can result in molecular-molecular 13

stacking, and the aggregated networks are formed. In addition, the amphiphilic nature of the cations of the target IPs favors the generation of the aggregates. 3.3. Experimental evidence of chemical adsorption 3.3.1. FT-IR spectroscopic and Raman spectroscopic evidence Figures 5 (a, b) show that the broad bands in the region of 3600-3300 cm-1 are produced by the remaining water molecules in the target copolymers, and the bands locating in 3300-2900 cm-1 are ascribed to C-H groups in the IP1 molecular skeleton. As compared to Figure 5a, Figure 5b suggests that the characteristic peak of the C=N (1561.3 cm-1) and the C-N bonding can not be discovered. The results indicate that the chemical chelation bonding between N-heterocyclic rings in the IP1-aggregates and Cu ions may be formed [48, 49]. The similar results are found in the IP2 (Figures S10 (a, b)).

Figure 5. (a) FT-IR spectra of the studied IP1, (b) the adsorbed surveyed IP1-aggregates on the investigated Cu substrates and (c) Raman spectra of the covered studied IP1-aggregates on the investigated Cu substrates.

The Raman spectra of the prepared IPs-aggregates modified Cu specimens are displayed in Figure 5c and Figure S10c. The peaks locating in 2840-3080 cm-1 and 3300-3600 cm-1 are yielded by the vibration of C-H groups derived from benzene ring and alkyl chain [50, 51]. Besides, no stretching of single chemical bonding or double chemical bonding between the carbon and the 14

nitrogen atoms range in 960-1280 cm-1 is discovered, while N:Cu bands situating in 390-570 cm-1 are found [52, 53]. The results further reflect the chemical interactions of the surveyed IPs aggregates with the Cu sample surfaces. 3.3.2. XPS evidence Figures 6-7 and Figure S11 present the XPS spectra acquired at 90° relative to the copper sample surface. Figure 6a compares the XPS survey spectra of bare copper and the studied IPs-aggregates covered copper (Cu-IP1 aggregates, Cu-IP2 aggregates), and the detection of N and Br elements from the target IPs-aggregates modified copper surfaces indicates the adsorption of the surveyed IPs-aggregates. The detected high-resolution XPS spectra of Cu 2p, C 1s, N 1s and Br 3d are resolved. The de-convolution parameters (Tables S(1-4)) including the chemical states, the binding energies, and the FWHMs (full width at half maximum) are supplied in Supplementary Materials.

Figure 6. (a) Representative XPS survey spectra of the bare Cu, the Cu samples covered by the stable IPs aggregates, respectively; (b) Representative XPS spectra of Cu 2p from surfaces of the bare Cu, the Cu samples treated by the stable IPs aggregates, respectively.

The typical double peaks of Cu 2p1/2 and Cu 2p3/2 are discovered, and their distance is 15

approximately 19.8 eV (such as in Figure 6b) [54]. It is found that the Cu 2p spectra of Cu-IPs aggregates exhibit no remarkable cupric satellite peaks between the Cu 2p1/2 and the Cu 2p3/2 peaks, which is distinct from the studied uncovered copper sample [55, 56].

Figure 7. XPS high-resolution spectra from the surfaces of uncovered copper (a) Cu 2p3/2, (c) C 1s, and IP1 aggregates covered copper (b) Cu 2p3/2, (d) C 1s, (e) N 1s, (f) Br 3d.

It further demonstrates that the Cu 2p3/2 peaks of Cu-IPs aggregates specimens are symmetric, but the Cu 2p3/2 peak of Cu-Bare surface are asymmetric [57]. Figure 7a reveals that the resolved 16

Cu 2p3/2 spectrum of Cu-Bare including two peaks, which are attributed to Cu(0)/Cu(I) and Cu(II). On the contrary, the Cu 2p3/2 spectra of IPs-aggregates-covered copper surfaces are not split, and only Cu(0)/Cu(I) components are contained (Figure 7b, Figure S11a). The results suggest that the covered IPs aggregates layers produced on the copper substrate may prevent the copper surfaces from the deep oxidation, and no Cu(II) species are detected on the IPs-aggregates adsorbed metal surfaces. Figures 7c-d and Figure S11b shows the de-convoluted C 1s XPS spectra of the detected Cu surfaces. Table S2 further lists the de-convolution parameters of C 1s spectra. Figure 7c presents three de-convoluted C 1s peaks of the bare copper surface locating at 284.78, 286.33 and 288.23 eV attributes to C-C, C-O-C and O-C=O components, respectively. The detected components are originated by the adventitious carbon contamination [58]. The IPs aggregates modified copper surface presents five de-convoluted C 1s peaks ascribed to C-C/C-H, C=N, C-O-C, C-N and O-C=O, respectively (Figure 7d and Figure S11b) [59-61]. The additional two components C=N and C-N are yielded by the IPs aggregates, reflect their adsorption on the studied Cu sample surface together with the adventitious carbon contamination. The N 1s spectra detected from surfaces of Cu-IP1 and Cu-IP2 are resolved into three peaks (Figure 7e, Figure S11c). Table S3 lists the de-convolution parameters of N 1s spectra. Two of the de-convoluted peaks are corresponding to C=N and C-N components [62, 63], while the left one is the characteristic peak of N:Cu, which is produced by the complexation process occurs between nitrogen and copper ions [64]. There are no N 1s spectra detected on the bare copper surface, which indicates the chemical coordination bonding resulting in the adsorption of IPs aggregates upon the studied Cu surface. 17

The high-resolution Br 3d XPS spectra can be de-convoluted into two peaks corresponding to the conventional Br 3d5/2 and Br 3d3/2 peaks, which are the characteristic peaks of Br- in the IP1 and IP2 aggregates (Figure 7f, Figure S11d) [65]. The corresponding de-convolution parameters are listed in Table S4. For the IP1-aggregates covered metal samples, the resolved Br 3d peaks locate at 69.32 eV (Br 3d5/2) and 70.18 eV (Br 3d3/2), which are similar to those of the IP2-aggregtes adsorbed copper specimen [66]. The Br 3d XPS spectra of Cu-IP1 and Cu-IP2 specimens further confirm the chemical chelation interactions of IPs aggregates with the surveyed copper surfaces. 3.4. XRD (X-ray diffraction) evidence The XRD patterns are acquired to determine the corrosion products of the unmodified copper and the stable IPs-aggregates modified copper samples (Cu-Bare, Cu-IP1, Cu-IP2) in aggressive sulfuric acid solution (Figure S12). The Cu-Bare presents three XRD peaks at 43.6°, 50.7°, 74.3° , which are corresponding to Cu, and the two other XRD peaks at 26.2°, 33.1° are yielded by CuO. In addition, the XRD peaks observed at 29.8°, 36.9°, 62.1°are produced by Cu2O [67, 68]. However, the XRD patterns of Cu-IP1 and Cu-IP2 display only the double peaks of cuprous oxide, but without the peaks of cupric oxide. The results indicate that the covered IPs-aggregates on copper surface suppress the further oxidation of the metal substrate. 3.5. Microscopic observation of the studied Cu specimen surfaces 3.5.1. SEM analyses of the studied Cu specimen surfaces Figure 8 displays the micrograph of the studied Cu sample surfaces. The freshly polished bare Cu surface exhibits the grinding marks such as the nicks and lines (Figure 8a). However, the surveyed corroded copper sample presents the seriously destroyed surface in the aggressive acid 18

medium (Figure 8b).

Figure 8. SEM micrographs of the studied copper specimen surfaces: (a) the freshly polished copper specimen, (b) immersed in 0.5 M H2SO4 solution for 48 h, (c) immersed in 0.5 M H2SO4 solution for 48 h with 0.100 g/L of IP1 aggregates yielded at 4 h aggregation time, (d) immersed in 0.5 M H2SO4 solution for 48 h with 0.200 g/L of IP1 aggregates formed at 4 h aggregation time, (e) immersed in 0.5 M H2SO4 solution for 48 h with 0.300 g/L of IP1 aggregates yielded at 4 h aggregation time.

Figures 8(c-e) and Figures S13(a-c) show the SEM images of the obtained stable IPs-aggregates covered copper sample surface. It is given that the IPs-aggregates of 0.100 g/L are adsorbed upon the Cu sample surface (such as in Figure 8c, Figure S13a). With the increasing concentrations of the surveyed IPs-aggregates (0.200 g/L), they are adsorbed on the entire metal substrates, and the grinding traces even can not be discovered (such as in Figure 8d, Figure S13b). However, the further increasing concentrations of the IPs-aggregates (0.300 g/L), the covered films look loose (such as in Figure 8e, Figure S13c). The results show that the more orderly IPs aggregates of 0.200 g/L lead to the stronger chemical binding with the studied metal 19

surface than the amorphous IPs-aggregates of 0.300 g/L. 3.5.2. AFM analyses of the studied copper specimen surfaces Figure S14 shows the 3D AFM images and homologous height profiles of the uncovered and covered Cu samples by the stable IPs-aggregates in aqueous H2SO4 acid solution for 2 h. The freshly burnished copper surface is smooth with the average roughness (Ra) of 2.6 nm (Figure S14a). However, the corroded uncovered copper surface displays the great changes in the aggressive acid medium, and the Ra value reaches 43.5 nm (Figure S14b). Figures S14(c, d) show that the adsorbed IPs aggregates cause the flat and uniform metal surfaces, which indicates that the covered IPs aggregates inhibit the corrosion of the studied metal specimen surfaces due to the aggressive acid ions. The relevant height profiles presented in Figures 14 (g, h) exhibit the slight fluctuation with the reduced Ra of the IPs-aggregates modified copper specimens (11.8 and 12.9 nm). Figure S15 further suggests that the studied copper specimens present the smoother surfaces covered by the more orderly IPs-aggregates of 0.200 g/L. 3.6. Corrosion resistance performance assessed by the electrochemical measurements 3.6.1. Potentiodynamic polarization determinations Figure 9 presents the Tafel plots of the investigated unmodified Cu electrodes (Blank), the stable IP1 and IP2 aggregates (yielded at 4 h aggregation) covered copper electrodes at 298 K, respectively. The anodic reaction of copper dissolution in aqueous acid solutions may be described by the Eqs. (6) and (7) [69], which reflects the dissolution of Cu electrode and transferring process from the Cu surface to the aggressive acid media. The cathodic reaction in acid solutions is typically considered as the oxygen reduction reaction (ORR) shown by the Eq. (8) [70]. 20

Cu → Cu+ + e-

(6)

Cu+ → Cu2+ + e-

(7)

O2 + 4H++ 4e- → 2H2O

(8)

Figure 9. Tafel curves in 0.5 M H2SO4 solution at 298 K for the investigated uncovered Cu electrodes (Blank) and the stable IP1-aggregates of various concentrations covered Cu electrodes for 2 h.

The Tafel curves (Figure 9 and Figure S16) show that both the cathodic and anodic branches of the stable IPs-aggregates modified copper electrodes shift to a lower position of the vertical axis, as compared to the bare copper. Besides, the cathodic curves show the more notably decrease tendency with the concentrations increasing from 0.025 g/L to 0.200 g/L. The results suggest that the process of oxygen reduction can be suppressed by the stable IPs-aggregates that are adsorbed upon the WEs, which thus effectively prevents the copper corrosion in the aggressive media. In addition, the parallel cathodic branches of the Tafel curves indicate that the reaction mechanism of cathodic branches are not varied with the adsorption amount of IPs aggregates on Cu electrode [71]. Table S5 lists the polarization parameters achieved from the Tafel plots which include the corrosion potential (Ecorr), corrosion current density (jcorr), cathodic Tafel slopes (βc), anodic Tafel 21

slopes (βa) and corrosion inhibition efficiencies (ηj). The parameters imply that the values of jcorr and CR show the decrease tendency with increasing the IPs-aggregates concentration rang in 0.025-0.200 g/L, and the minimal value is gained at 0.200 g/L. Furthermore, the corrosion inhibition efficiency ηj reaches the maximal value (96.3% for the IP1 aggregates, 95.2% for the IP2 aggregates). However, ηj shows a decrease at 0.300 g/L, which suggests that the produced disorderly aggregates cover on Cu WEs loosely. In addition, the values of Ecorr show the similar change tendency with enhancing the concentrations of the IPs-aggregates, and it becomes more remarkable in the negative direction. This phenomenon further confirms that the studied IPs-aggregates can protect the copper in sulfuric acid medium primarily through controlling the cathodic electrode reaction, which involves the ORR process. The close slop values (βa, βb) of the Tafel curves for the covered copper electrodes by various concentrations of the IPs-aggregates further demonstrates the similar mechanism of the cathodic and anodic electrode reaction. 3.6.2. Electrochemical impedance spectroscopy determinations Figure 10a (the IP1 aggregates) and Figure S17a (the IP2 aggregates) display the homologous Nyquist diagrams detected in 0.5 M H2SO4 solution at room temperature for the bare Cu sample (Blank) and the stable IPs-aggregates of different concentrations covered Cu specimens. It is shown that the Nyquist plot of the naked Cu electrode includes a depressed capacitive semicircle in the high frequency (HF) range, followed by a straight line in the low frequency (LF) region. The semicircle is ascribed to the charge-transport process of Cu dissolving. The straight line is ascribed to the Warburg impedance which is related to the migration of dissolved oxygen molecules in the bulk solution, or the corrosion products, or the aggressive 22

species.

Figure 10. (a) Nyquist, (b) Bode plots, in 0.5 M H2SO4 solution at 298 K for the studied naked copper electrodes and the stable IP1-aggregates of various concentrations (formed at 4 h aggregation) covered copper electrodes obtained at 2 h.

For the stable IPs-aggregates covered copper electrodes, the diameters of the capacitive arcs show the increase, and no Warburg impedance is presented (Figure 10a and Figure S17a). The disappearance of the Warburg impedance suggests that the diffusion process may be effectively restricted by the covered IPs-aggregates. In addition, the capacitive arcs of IPs-aggregates adsorbed copper electrodes display the increase tendency with improving the concentrations of the stable IPs-aggregates in 0.025-0.200 g/L. However, the capacitive arc diminishes as the concentration increases to 0.300 g/L, which demonstrates again that the corrosion inhibition performance of the IPs-aggregates may decrease at the amorphous aggregation state owing to the weak adsorption on the studied WEs surface. The Bode plots (Figure 10b and Figure S17b) imply that the impedance values increase in the defined frequency range with the IPs-aggregates concentrations increasing from 0.025 to 0.200 g/L, and the maximal value achieves at 0.200 g/L. Furthermore, the largest phase angles increase with the enhancing concentrations of the IPs-aggregates (0.025-0.200 g/L) within the determined frequency regions. However, the impedance values and the phase angle values of the 23

0.300 g/L IPs-aggregates adsorbed copper electrode decrease. Additionally, it is noticed that the IPs-aggregates covered copper shows the broader region of phase angles as compared to the uncovered copper, which may be due to the more remarkable inhibition nature.

Figure 11. Equivalent circuit models suitable the EIS experimental data: (a) Blank copper sample, (b) the stable IPs-aggregates modified copper sample.

The electrochemical parameters obtained by fitting the equivalent circuits (R(Q(R(Q(RW)))), Figure 11a, R(Q(R(Q(R)))), Figure 11b) through ZSimpWin software are listed in Table S6. Besides, the chi-squares suggesting that the above equivalent circuits match well with the experimental results. As depicted in Figure 11 and Table S6, Rs shows the resistance of the solution between WEs and REs, Rct represents the charge transfer resistance, and Rpore is the resistance of pore solution, W means the Warburg impedance. Furthermore, the constant phase element CPEf consists of the membrane capacitance Cf and the deviation parameter n1 , and CPEdl includes the double-layer capacitance Cdl and the deviation parameter n2 . In addition, the impedance of CPE may be described by Eq. (9) [72]: Z CPE 

1 Y ( jω )

(9)

n

wherein Y is the admittance of the electrochemical system, j shows the imaginary root, ω is the angular frequency, n represents the deviation parameter. If n = 0, CPE becomes a pure resistor, 24

and for n = 1, means a pure capacitor. Furthermore, the capacitance values of Cdl can be calculated from the value of Y and n obtained by the Eq. (10) [73].

Cdl =

Yω

n -1 (10)

sin( nπ 2)

Table S6 reflects that the fitted values of Rct and Rpore increase with the enhancing concentrations of the investigated IPs-aggregates in 0.025-0.200 g/L, which may be resulted by the adsorbed protective layers upon WEs. Besides, the values of Cf and Cdl decrease with the adsorption of the IPs-aggregates, which can be resulted from the replacement of water molecules as well as the aggressive species by the adsorbed IPs-aggregates, and thus leading to the reduced contacting areas of WEs with the aggressive media [74]. By increasing the concentrations of the IPs-aggregates in range of 0.025-0.200 g/L, the coverage areas of the formed protective film increase. Thus, the thickness of electric double-layer increases, and the local dielectric constant decreases. These factors result in the decreases of the Cf and Cdl values. Thus, the corrosion inhibition efficiency ηz reaches the largest value of 97.8% for the IP1-aggregates and 96.8% for IP2-aggregates at 0.200 g/L. It is noticed that the corrosion inhibition efficiencies of the IPs aggregates based on EIS are found to be greater that those of the reported organic inhibitors in 0.5 mol/L H2SO4 (Table S7). The IP2-aggregates present a little lower corrosion inhibition efficiency than the IP1-aggregates, which may be ascribed to the smaller sizes of the IP2-aggregates and the different molecular structure of the IP2. However, the corrosion inhibition efficiency ηz of the IPs-aggregates of 0.300 g/L shows the decrease, which is mostly due to that the amorphous aggregation state may produce the weak adsorption upon the studied Cu surface. 3.7. Effect of corrosion temperature and kinetic parameters 25

In order to study the temperature effect on copper corrosion process and obtain the kinetic parameters, the Tafel plots of copper electrodes unmodified and modified by 0.2 g/L IPs aggregates are acquired at the higher temperature of 308 K, 318 K, 328 K, 338 K in 0.5 M H2SO4 solution, which are given in Figure 12 and Figure S18. The polarization parameters including Ecorr, jcorr, βc, βa, ηj and CR detected at different temperature are listed in Table S8.

Figure 12. Tafel curves in 0.5 M sulfuric acid solution at various temperatures for the surveyed unmodified copper electrodes (Blank) and the stable 0.2 g/L IP1-aggregates covered Cu electrodes for 2 h.

It can be deduced that with increasing the temperature, the values of jcorr and CR increase along with the decrease of ηj. The phenomena may be induced by the faster damage of the oxide film for the uncovered copper electrodes, the desorption and/or rearrangement of the IPs aggregates for the covered copper electrodes at the higher temperature[75]. To further investigate the temperature effect on copper corrosion, the activation parameters for the corrosion process and the temperature dependency of CR are fitted by the Arrhenius equation as shown in Eq. (11) [32]: lnCR = lnA 

Ea RT

(11)

wherein, CR is the corrosion rate in mpy, Ea shows the apparent activation energy, A represents the Arrhenius pre-exponential factor, R is the universal gas constant, T represents the absolute 26

temperature. As shown in Figure 13, the apparent activation energy (Ea) at the optimal concentration of the IPs aggregates is calculated by linear regression between ln Rcorr and 1/T. Typically, the calculated values of the apparent activation energy Ea of the inhibitor-modified specimens are larger than that of the unmodified one, meaning that a physical (electrostatic) adsorption could be presence [32, 76, 77]. In this study, the determined values of Ea are 29.50 kJ.mol-1 for the Blank, 49.55 kJ.mol-1 for the IP1 aggregates, 46.72 kJ.mol-1 for the IP2 aggregates. Thus, the physical adsorption during the adsorption process of the IPs aggregates upon Cu surface could occur.

Figure 13. Arrhenius plots of ln CR vs. 1/T for copper in 0.5 M H2SO4 solution unmodified and modified by the optimal concentrations of the IPs aggregates.

3.8. Adsorption isotherm plots The typically four types of adsorption isotherms containing Temkin, Freundlich, Flory-Huggins and Langmuir isotherms were derived by the linear regression between the surface coverages and the concentrations of the IPs-aggregates. The Langmuir isotherm (Eq. 12) is the most ideal model to acquire the linear regression coefficient (R2) closing to 1 [78]:

1 c  c θ K ads

(12)

27

wherein, θ is the surface coverage determined by the inhibition efficiency (η) achieved from the electrochemical determination, Kads shows the equilibrium constant of the adsorption, and c represents the concentration of the IPs-aggregates.

Figure 14. Langmuir adsorption isotherm of the stable IP1 aggregates adsorbed upon the studied Cu specimen surfaces in 0.5 M H2SO4 solution at 298 K (yP to potentiodynamic polarization, yE to electrochemical impedance spectroscopy).

The plots of c/θ as the function of c show the straight lines with an intercept of 1/K, which are presented in Figure 14 and Figure S19. The standard adsorption free energy Gads can be 0

calculated by the Eq. (13) [79]: 0 Gads   RTln( 1  103 K ads )

(13)

wherein, R is the universal gas constant, and T shows the absolute temperature. A higher value of Kads typically implies that the investigated inhibition species display the stronger adsorption on the studied metal surface. Furthermore, it is well known that a Gads value of -20 kJ/mol or less 0

negative, the physisorption may play a key role. In addition, if the value of Gads is -40 kJ/mol 0

or more negative, the chemisorption can be primary [80, 81]. Figure 14 and Figure S19 suggest that the calculated values of Gads are in around -30 kJ/mol, which means the mix-type 0

28

physisorption and chemisorption of the surveyed IPs-aggregates on the investigated Cu specimen surfaces. 3.8. Molecular modeling The electron density distribution originating from the frontier orbitals and the Mulliken charge distribution of IP1 and IP2 repeating segments are presented in Figure 15 and Figure S20. The HOMOs of the IP1 and IP2 repeating segments are mainly concentrated in benzene ring or alkyl chain, and the LUMOs of IPs repeating segments locate in the part of imidazolinium ring and benzene ring or alkyl chain. The acquired results suggest that imidazolinium ring parts of the IPs play crucial roles in the chemical coordination with copper ions. It is noticed that the IP1 repeating unit shows a lower energy gap as compared to the IP2 repeating unit (IP1, ΔE=0.131 eV, IP2, ΔE=0.215 eV), which reflects the greater chemical chelating of the IP1 with the copper substrate [82].

Figure 15. The optimized structures, frontier orbital density distributions, and Mulliken charge for the studied IP1 repeating segments.

The Mulliken charge is calculated to further investigate the local reactivity of single atom in 29

the IPs compund, which could be employed to determine the mostly contributed atoms in donating electrons to copper surface [83]. The obtained Mulliken charge distribution of the IPs repeating segments reveals that the electronegative atoms (red color) include nitrogen atoms root in imidazolinium rings, carbon atoms root in benzene rings, and carbon atoms root in -CH2 or CH3 (actually -CH2 in IPs). It is noticed that the nitrogen atoms root in the imidazolinium rings of the IPs are mostly negative (around -0.40 e), implies the strongest reactivity with cuprous ions. 3.9. Molecular dynamic simulations The molecular dynamic (MD) simulations further reveal the details of the IPs repeating segments motions in the atomic level, which presents the more details of inhibition process of the IPs aggregates on copper surface in acid aggressive medium. As shown in Figure 16 and Figure S21, the optimal configurations of the IPs repeating segments-Cu (1 1 1) surface adsorption system under the equilibrium conditions with the steady fluctuation of temperature and energy are obtained.

Figure 16. Side (a) and top (b) views of the equilibrium configurations for the IP1 repeating unit adsorbed on Cu (111) surface in 0.5 M H2SO4 solution.

From the side and top view of the configurations (Figure 15a, Figure S21a), the IPs 30

repeating segments attach tightly and approximately parallel with the Cu surface. As a result, the chelation bond could form between the N atoms in IPs segments and copper surface. Similarly, the adsorbed IPs aggregates in the parallel orientation with a maximal surface coverage can efficiently prevent the contact of water and acid medium on copper surface. Additionally, the calculated adsorption energies and binding energies for the further quantificational study of the adsorption capability of the IPs repeating segments on copper surface are listed in Table S9. Typically, a smaller Eadsorption demonstrates a spontaneous, strong, and stable adsorption process [84]. On the contrary, a higher value of Ebinding indicates a more steady adsorption system. Thus, the corrosion inhibitor may efficiently protect the metal surface in corrosive medium. Therefore, the efficient anti-corrosion capability of the IPs can be determined by the large Ebinding value of 100.12 kcal mol−1 (the IP1 repeating segment) and 79.67 kcal mol−1 (the IP2 repeating segment). The results may also undertstand the covered IPs aggregates film on the metal surface determined by the micrograph analysis and the high inhibition efficiency. 3.10. Adsorption mechanism and anti-corrosion mechanism The chemical chelation between the IPs aggregates and Cu substrate is confirmed by FT-IR, Raman, and XPS characterizations. The XRD analysis further shows that the corrosion products of IPs-aggregates covered copper surface are mainly attributed to the cuprous oxide. Thus, the chelation bonding between nitrogen and cuprous ion plays a crucial role for the IPs aggregates in forming the chemical interaction with copper slab. On the other hand, the obtained value of CR by the polarization tests at various temperatures are in good accordance with the Arrhenius equation, and the calculated values of activation energy (Ea) further indicate the accompanying physisorption occurrence in the adsorption process of the IPs aggregates on Cu surface. The 31

simultaneous presence of chemisorption and physisorption is further demonstrated by the Langmuir isotherm plots through the calculated values of Gads . 0

The molecular modeling results reveal the localized distribution of HOMOs and LUMOs suggests that imidazolinium ring parts of the IPs is significant in the chemical coordination with copper ions. The lower energy gap reflects the stronger chemical chelating. Moreover, the MD simulation presents the parallel orientated equilibrium configurations of the IPs repeating segments on Cu(1 1 1) surface in 0.5 M H2SO4 aqueous solution, and the maximal coverage area can be determined. The calculated small value of Eadsorption and the large Ebinding value reflect the strong adsorption strength of the IPs aggregates on copper surface. Scheme 2 shows a concise diagram of the corrosion inhibition mechanism. The self-assembly target IPs aggregates can form protective film on the surveyed copper surface through the strong chemical chelation interaction with Cu substrate along with the physisorption on copper electrode. The electrochemical measurements suggest that the IPs aggregates layers may control both the anodic and cathodic corrosion reactions, and primarily the cathodic reaction in sulfuric acid solution efficiently. Thus, the covered IPs aggregates display notable anti-corrosion performance on copper electrode with the decreased jcorr and increased Rct.

Scheme 2. A concise diagram of anti-corrosion mechanism. 32

4. Conclusions In summary, this study prepares two new IPs based on rigid aromatic phenylmethyl-linked bisimidazole and dibromide derivatives copolymerization that can process self-assembly in 0.5 M aqueous sulfuric acid solution. The sizes and morphologies of the yielded IPs-aggregates are shown dependence on the assembly concentrations and time. Furthermore, the chemical chelating bonding between the IPs-aggregates and Cu substrate is demonstrated by the FT-IR, Raman, XPS and XRD spectroscopy. The chemical chelation occurs primarily through nitrogen atoms and Cu(I), resulting in the formation of protective films upon the studied copper substrates. In addition, the physisorption in the adsorption process of the IPs aggregates on metal surface can occur based on the polarization tests at various temperatures. The electrochemical measurements suggesting that the IPs aggregates layers may control both the anodic and cathodic corrosion reactions, and primarily control the cathodic reaction in sulfuric acid solution efficiently. Hence, the neat anti-corrosion performance of Cu in aggressive acid medium is reached. The molecular modeling further reveals that the imidazolinium cycles can be the active centers chelating with copper surface, and the most electronegative nitrogen atoms present the strongest reactivity with cuprous ions. The MD simulation reveals that the parallel orientated equilibrium configurations of the IPs aggregates form the maximal coverage areas on copper slab, along with the strong adsorption strength determined by the calculated binding energy (Ebinding). The results presented herein benefit us to develop new organic corrosion inhibitors for various metals in aggressive acid medium. Supplementary Data The supplementary materials associated with this study can be found in the online version, at 33

http://dx.doi.org/XXXX. Detail synthesis and characterization of monomers and the target IPs, characterization results and discussions for the IP2 aggregates, OCP curves, DSC curves, TEM images, DLS plots, Zeta potentials; SEM images; UV/visible absorption spectra; XRD patterns; AFM images; FT-IR spectra, Raman spectra; Tafel curves; Nyquist plots and Bode plots; Langmuir adsorption isotherm; molecular modeling results; MD results; 1H NMR and

13C-NMR

spectra of monomers and the IPs; XPS resolved parameters; polarization parameters; electrochemical impedance parameters, the calculated energies. Acknowledgements We thank the supporting of NSFC of China (# 21376282, 21676035, 21878029). We shall give

our

appreciation

to

Chongqing

Science

and

Technology

Commission

(#

cstc2018jcyjAX0668). H. L. thanks China Postdoctoral Science Foundation (# 22012T50762 & 2011M501388). H.-J. H thanks Graduate Student Research Innovation Project, Chongqing University (CYB18046). Z. W. shall express his thanks to the Fundamental Research Funds for the Central Universities (# 2018CDXYHG0028). We shall specially thank Prof. Xinzheng Li of Peking University for his warm help in the molecular modeling. We appreciate greatly the warm help from Analytical and Testing Center of Chongqing University. References [1] S. Pareek, D. Jain, S. Hussain, A. Biswas, R. Shrivastava, S.K. Parida, H.K. Kisan, H. Lgaz, I.-M. Chung, D. Behera, A new insight into corrosion inhibition mechanism of copper in aerated 3.5 wt.% NaCl solution by eco-friendly Imidazopyrimidine Dye: experimental and theoretical approach, Chem. Eng. J. 358 (2019) 725-742. [2] M. Mousavi, T. Baghgoli, Application of interaction energy in quantitative structure-inhibition 34

relationship study of some benzenethiol derivatives on copper corrosion, Corros. Sci. 105 (2016) 170-176. [3] Z. Wang, Y. Gong, L. Zhang, C. Jing, F. Gao, S. Zhang, H. Li, Self-assembly of new dendrimers basing on strong π-π intermolecular interaction for application to protect copper, Chem. Eng. J. 342 (2018) 238-250. [4] G. Žerjav, I. Milošev, Protection of copper against corrosion in simulated urban rain by the combined action of benzotriazole, 2-mercaptobenzimidazole and stearic acid, Corros. Sci. 98 (2015) 180-191. [5] M.A. Hegazy, A.A. Nazeer, K. Shalabi, Electrochemical studies on the inhibition behavior of copper corrosion in pickling acid using quaternary ammonium salts, J. Mol. Liq. 209 (2015) 419-427. [6] M. Bozorg, T. Shahrabi Farahani, J. Neshati, Z. Chaghazardi, G. Mohammadi Ziarani, Myrtus communis as green inhibitor of copper corrosion in sulfuric acid, Ind. Eng. Chem. Res. 53 (2014) 4295-4303. [7] R. Solmaz, E. Altunbaş Şahin, A. Döner, G. Kardaş, The investigation of synergistic inhibition effect of rhodanine and iodide ion on the corrosion of copper in sulphuric acid solution, Corros. Sci. 53 (2011) 3231-3240. [8] A. Zarrouk, B. Hammouti, A. Dafali, F. Bentiss, Inhibitive properties and adsorption of purpald as a corrosion inhibitor for copper in nitric acid medium, Ind. Eng. Chem. Res. 52 (2013) 2560-2568. [9] H. Gerengi, M. Mielniczek, G. Gece, M.M. Solomon, Experimental and quantum chemical evaluation of 8-Hydroxyquinoline as a corrosion inhibitor for copper in 0.1 M HCl, Ind. Eng. Chem. Res. 55 (2016) 9614-9624. [10] L. Guo, I.B. Obot, X. Zheng, X. Shen, Y. Qiang, S. Kaya, C. Kaya, Theoretical insight into an 35

empirical rule about organic corrosion inhibitors containing nitrogen, oxygen, and sulfur atoms, Appl. Surf. Sci. 406 (2017) 301-306. [11] Y. Qiang, S. Fu, S. Zhang, S. Chen, X. Zou, Designing and fabricating of single and double alkyl-chain indazole derivatives self-assembled monolayer for corrosion inhibition of copper, Corros. Sci. 140 (2018) 111-121. [12] R. Fuchs-Godec, G. Zerjav, Corrosion resistance of high-level-hydrophobic layers in combination with Vitamin E – (α-tocopherol) as green inhibitor, Corros. Sci. 97 (2015) 7-16. [13] M. Joo, J. Shin, J. Kim, J.B. You, Y. Yoo, M.J. Kwak, M.S. Oh, S.G. Im, One-step synthesis of cross-linked ionic polymer thin films in vapor phase and its application to an oil/water separation membrane, J. Am. Chem. Soc. 139 (2017) 2329-2337. [14] F. Fan, Y. Wang, T. Hong, M.F. Heres, T. Saito, A.P. Sokolov, Ion conduction in polymerized ionic liquids with different pendant groups, Macromolecules 48 (2015) 4461-4470. [15] J. Yuan, M. Antonietti, Poly(ionic liquid)s: Polymers expanding classical property profiles, Polymer 52 (2011) 1469-1482. [16] M. González-Burgos, J.A. Pomposo, Mapping the extra solvent power of ionic liquids for monomers, polymers, and dry/wet globular single-chain polymer nanoparticles, Langmuir 34 (2018) 3275-3282. [17] D. Mecerreyes, Polymeric ionic liquids: Broadening the properties and applications of polyelectrolytes, Prog. Polym. Sci. 36 (2011) 1629-1648. [18] O. Green, S. Grubjesic, S. Lee, M.A. Firestone, The design of polymeric ionic liquids for the preparation of functional materials, Polym. Rev. 49 (2009) 339-360. [19] J. Lu, F. Yan, J. Texter, Advanced applications of ionic liquids in polymer science, Prog. Polym. 36

Sci. 34 (2009) 431-448. [20] Y. Yang, J. Zheng, S. Man, X. Sun, Z. An, Synthesis of poly(ionic liquid)-based nano-objects with morphological transitions via RAFT polymerization-induced self-assembly in ethanol, Polym. Chem. 9 (2018) 824-827. [21] A.M. Atta, M.M.S. Abdullah, H.A. Al-Lohedan, A.K. Gaffer, Synthesis and application of amphiphilic poly(ionic liquid) dendron from cashew nut shell oil as a green oilfield chemical for heavy petroleum crude oil emulsion, Energ. Fuel. 32 (2018) 4873-4884. [22] M. Taghavikish, S. Subianto, N. Roy Choudhury, N.K. Dutta, Effect of polymerized ionic liquid based gel inhibitor on electrochemical performance of self-assembled nanophase coating, Prog. Org. Coat. 120 (2018) 143-152. [23] S.K. Hwang, T.J. Park, K.L. Kim, S.M. Cho, B.J. Jeong, C. Park, Organic one-transistor-type nonvolatile memory gated with thin ionic liquid-polymer film for low voltage operation, ACS Appl. Mater. Inter. 6 (2014) 20179-20187. [24] Y. Li, Y. Song, X. Zhang, X. Wu, F. Wang, Z. Wang, Programmable polymer memory device based on hydrophilic polythiophene and poly(ionic liquid) electrolyte, Macromol. Chem. Phys. 216 (2014) 113-121. [25] X. Zhu, Y. Zeng, Z. Zhang, Y. Yang, Y. Zhai, H. Wang, L. Liu, J. Hu, L. Li, A new composite of graphene and molecularly imprinted polymer based on ionic liquids as functional monomer and cross-linker for electrochemical sensing 6-benzylaminopurine, Biosens. Bioelectron. 108 (2018) 38-45. [26] Y. Wang, C. Li, T. Wu, X. Ye, Polymerized ionic liquid functionalized graphene oxide nanosheets as a sensitive platform for bisphenol a sensing, Carbon 129 (2018) 21-28. [27] A. Vizintin, R. Guterman, J. Schmidt, M. Antonietti, R. Dominko, Linear and cross-linked ionic 37

liquid polymers as binders in lithium–sulfur batteries, Chem. Mater. 30 (2018) 5444-5450. [28] J. Maiti, N. Kakati, S.P. Woo, Y.S. Yoon, Nafion® based hybrid composite membrane containing GO and dihydrogen phosphate functionalized ionic liquid for high temperature polymer electrolyte membrane fuel cell, Compos. Sci. Technol. 155 (2018) 189-196. [29] W. Hong, C. Meis, J.R. Heflin, R. Montazami, Evidence of counterion migration in ionic polymer actuators via investigation of electromechanical performance, Sensor. Actuat. B: Chem. 205 (2014) 371-376. [30] A. Muñoz-Bonilla, M. Fernández-García, Poly(ionic liquid)s as antimicrobial materials, Eur. Polym. J. 105 (2018) 135-149. [31] H. Huang, Y. Fu, X. Wang, Y. Gao, Z. Wang, S. Zhang, H. Li, F. Gao, L. Chen, Nano- to micro-self-aggregates of new bisimidazole-based copoly(ionic liquid)s for protecting copper in aqueous sulfuric acid solution, ACS Appl. Mater. Inter. 11 (2019) 10135-10145. [32] L.H. Madkour, S. Kaya, I.B. Obot, Computational, Monte Carlo simulation and experimental studies of some arylazotriazoles (AATR) and their copper complexes in corrosion inhibition process, J. Mol. Liq. 260 (2018) 351-374. [33] S. Qiu, W. Li, W. Zheng, H. Zhao, L. Wang, Synergistic effect of polypyrrole-intercalated graphene for enhanced corrosion protection of aqueous coating in 3.5% NaCl solution, ACS Appl. Mater. Inter. 9 (2017) 34294-34304.

[34] M. Frisch, G. Trucks, H. Schlegel, G. Scuseria, M. Robb, J. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. Petersson, Gaussian 09, Revision A. 02; Gaussian, Inc: Wallingford, CT, 2009. [35] B. Tan, S. Zhang, H. Liu, Y. Guo, Y. Qiang, W. Li, L. Guo, C. Xu, S. Chen, Corrosion inhibition 38

of X65 steel in sulfuric acid by two food flavorants 2-isobutylthiazole and 1-(1,3-Thiazol-2-yl) ethanone as the green environmental corrosion inhibitors: Combination of experimental and theoretical researches, J. Colloid Interf. Sci. 538 (2019) 519-529.

[36] Y. Qiang, S. Zhang, L. Guo, X. Zheng, B. Xiang, S. Chen, Experimental and theoretical studies of four allyl imidazolium-based ionic liquids as green inhibitors for copper corrosion in sulfuric acid, Corros. Sci. 119 (2017) 68-78.

[37] T. Semoto, Y. Tsuji, K. Yoshizawa, Accelrys Materials Studio 5.5, 2011, B. Chem. Soc. Japan 85 (2012) 672-678. [38] L. Vitos, A.V. Ruban, H.L. Skriver, J. Kollár, The surface energy of metals, Surf. Sci. 411 (1998) 186-202. [39] F. Li, M. Bai, S.a. Wei, S. Jin, W. Shen, Multidimension insight involving experimental and in silico investigation into the corrosion inhibition of N,N-dibenzyl dithiocarbamate acid on copper in sulfuric acid solution, Ind. Eng. Chem. Res. 58 (2019) 7166-7178. [40] Y. Qiang, S. Zhang, S. Yan, X. Zou, S. Chen, Three indazole derivatives as corrosion inhibitors of copper in a neutral chloride solution, Corros. Sci. 126 (2017) 295-304. [41] S. Sun, Y. Geng, L. Tian, S. Chen, Y. Yan, S. Hu, Density functional theory study of imidazole, benzimidazole and 2-mercaptobenzimidazole adsorption onto clean Cu(111) surface, Corros. Sci. 63 (2012) 140-147. [42] B. Tan, S. Zhang, W. Li, X. Zuo, Y. Qiang, L. Xu, J. Hao, S. Chen, Experimental and theoretical studies on inhibition performance of Cu corrosion in 0.5 M H2SO4 by three disulfide derivatives, J. Ind. Eng. Chem. 77 (2019) 449-460. [43] P. Hu, W. Dai, Computer simulation and density functional theory study on relationship between 39

structure of amino acid and inhibition performance, Mater. Res. Innov. 16 (2012) 67-72. [44] N.-W. Pu, C.-A. Wang, Y. Sung, Y.-M. Liu, M.-D. Ger, Production of few-layer graphene by supercritical CO2 exfoliation of graphite, Mater. Lett. 63 (2009) 1987-1989. [45] A.L. Lorenzen, T.S. Rossi, I.C. Riegel-Vidotti, M. Vidotti, Influence of cationic and anionic micelles in the (sono)chemical synthesis of stable Ni(OH)2 nanoparticles: “In situ” zeta-potential measurements and electrochemical properties, Appl. Surf. Sci. 455 (2018) 357-366. [46] H. Li, Y. Zhang, B. Chen, Y. Wang, C. Teh, G.H.B. Ng, J. Meng, Z. Huang, W. Dong, M.Y. Tan, X. Sun, X. Sun, X. Li, J. Li, J-Aggregation of perylene diimides in silica nanocapsules for stable near-infrared photothermal conversion, ACS Appl. Bio Mater. 2 (2019) 1569-1577. [47] Y. Qiu, H. Hu, D. Zhao, J. Wang, H. Wang, Q. Wang, H. Peng, Y. Liao, X. Xie, Concentration-dependent dye aggregation and disassembly triggered by the same artificial helical foldamer, Polymer 170 (2019) 7-15. [48] S. García-Fernández, I. Gandarias, J. Requies, F. Soulimani, P.L. Arias, B.M. Weckhuysen, The role of tungsten oxide in the selective hydrogenolysis of glycerol to 1,3-propanediol over Pt/WOx/Al2O3, Appl. Catal. B: Environ. 204 (2017) 260-272. [49] D. Stoian, A. Bansode, F. Medina, A. Urakawa, Catalysis under microscope: Unraveling the mechanism of catalyst de- and re-activation in the continuous dimethyl carbonate synthesis from CO2 and methanol in the presence of a dehydrating agent, Catal. Today 283 (2017) 2-10. [50] J. Du, Y. Ying, X.-y. Guo, C.-c. Li, Y. Wu, Y. Wen, H.-F. Yang, Acetohydroxamic acid adsorbed at copper surface: electrochemical, Raman and theoretical observations, Int. J. Ind. Chem. 8 (2017) 285-296. [51] G. Rajkumar, R. Sagunthala, M.G. Sethuraman, Investigation of inhibiting properties of 40

self-assembled films of 4-aminothiophenol on copper in 3.5% NaCl, J. Adhes. Sci. Technol. 29 (2015) 1107-1117. [52] P. Song, S. Shen, C.-C. Li, X.-Y. Guo, Y. Wen, H.-F. Yang, Insight in layer-by-layer assembly of cysteamine and l-cysteine on the copper surface by electrochemistry and Raman spectroscopy, Appl. Surf. Sci. 328 (2015) 86-94. [53] W. Yang, T. Li, H. Zhou, Z. Huang, C. Fu, L. Chen, M. Li, Y. Kuang, Electrochemical and anti-corrosion properties of octadecanethiol and benzotriazole binary self-assembled monolayers on copper, Electrochim. Acta 220 (2016) 245-251. [54] W. Jiao, Y. Cheng, J. Zhang, R. Che, Self-assembled 3D hierarchical copper hydroxyphosphate modified by the oxidation of copper foil as a recyclable, wide wavelength photocatalyst, Langmuir 33 (2017) 13649-13656. [55] S. Ahn, K. Klyukin, R.J. Wakeham, J.A. Rudd, A.R. Lewis, S. Alexander, F. Carla, V. Alexandrov, E. Andreoli, Poly-amide modified copper foam electrodes for enhanced electrochemical reduction of carbon dioxide, ACS Catal. 8 (2018) 4132-4142. [56] Y. Wang, F. Lin, J. Peng, Y. Dong, W. Li, Y. Huang, A robust bilayer nanofilm fabricated on copper foam for oil–water separation with improved performances, J. Mater. Chem. A 4 (2016) 10294-10303. [57] D.S. Bergsman, T.-L. Liu, R.G. Closser, K.L. Nardi, N. Draeger, D.M. Hausmann, S.F. Bent, Formation and ripening of self-assembled multilayers from the vapor-phase deposition of dodecanethiol on copper oxide, Chem. Mater. 30 (2018) 5694-5703. [58] A. Cánneva, I.S. Giordana, G. Erra, A. Calvo, Organic matter characterization of shale rock by X-ray photoelectron spectroscopy: adventitious carbon contamination and radiation damage, Energ. 41

Fuel. 31 (2017) 10414-10419. [59] T.I.T. Okpalugo, P. Papakonstantinou, H. Murphy, J. McLaughlin, N.M.D. Brown, High resolution XPS characterization of chemical functionalised MWCNTs and SWCNTs, Carbon 43 (2005) 153-161. [60] J. Landoulsi, M.J. Genet, S. Fleith, Y. Touré, I. Liascukiene, C. Méthivier, P.G. Rouxhet, Organic adlayer on inorganic materials: XPS analysis selectivity to cope with adventitious contamination, Appl. Surf. Sci. 383 (2016) 71-83. [61] E. Vassallo, A. Cremona, F. Ghezzi, F. Dellera, L. Laguardia, G. Ambrosone, U. Coscia, Structural and optical properties of amorphous hydrogenated silicon carbonitride films produced by PECVD, Appl. Surf. Sci. 252 (2006) 7993-8000. [62] G. Xue, J. Ding, Chemisorption of a compact polymeric coating on copper surfaces from a benzotriazole solution, Appl. Surf. Sci. 40 (1990) 327-332. [63] W. Zhou, G. Li, L. Wang, Z. Chen, Y. Lin, A facile method for the fabrication of a superhydrophobic polydopamine-coated copper foam for oil/water separation, Appl. Surf. Sci. 413 (2017) 140-148. [64] A. Mezzi, E. Angelini, T. De Caro, S. Grassini, F. Faraldi, C. Riccucci, G.M. Ingo, Investigation of the benzotriazole inhibition mechanism of bronze disease, Surf. Interface Anal. 44 (2012) 968-971. [65] C. Hua, X. Dong, Y. Wang, N. Zheng, H. Ma, X. Zhang, Synthesis of a BiOCl1−xBrx@AgBr heterostructure with enhanced photocatalytic activity under visible light, RSC Adv. 8 (2018) 16513-16520. [66] B. Wang, J. Di, P. Zhang, J. Xia, S. Dai, H. Li, Ionic liquid-induced strategy for porous perovskite-like PbBiO2 Br photocatalysts with enhanced photocatalytic activity and mechanism insight, Appl. Catal. B: Environ. 206 (2017) 127-135. 42

[67] H. Wang, J. Yu, Y. Wu, W. Shao, X. Xu, A facile two-step approach to prepare superhydrophobic surfaces on copper substrates, J. Mater. Chem. A 2 (2014) 5010-5017. [68] W. Lou, W. Cai, P. Li, J. Su, S. Zheng, Y. Zhang, W. Jin, Additives-assisted electrodeposition of fine spherical copper powder from sulfuric acid solution, Powder Technol. 326 (2018) 84-88. [69] A. Yurt, G.z. Bereket, Combined electrochemical and quantum chemical study of some diamine derivatives as corrosion inhibitors for copper, Ind. Eng. Chem. Res. 50 (2011) 8073-8079. [70] B. Duran, G. Bereket, Cyclic voltammetric synthesis of poly(N-methyl pyrrole) on copper and effects of polymerization parameters on corrosion performance, Ind. Eng. Chem. Res. 51 (2012) 5246-5255. [71] A. Doner, A.O. Yuce, G. Kardas, Inhibition effect of Rhodanine-N-Acetic acid on copper corrosion in acidic media, Ind. Eng. Chem. Res. 52 (2013) 9709-9718. [72] D. Fu, Study on the corrosion inhibition effect of 2,3-Dimercapto-1- propanol on copper in 0.5 mol/L H2SO4 solution, Int. J. Electrochem. Sci. (2018) 8561-8574. [73] Y. Xu, S. Zhang, W. Li, L. Guo, S. Xu, L. Feng, L.H. Madkour, Experimental and theoretical investigations of some pyrazolo-pyrimidine derivatives as corrosion inhibitors on copper in sulfuric acid solution, Appl. Surf. Sci. 459 (2018) 612-620. [74] Q. Qu, S. Li, L. Li, L. Zuo, X. Ran, Y. Qu, B. Zhu, Adsorption and corrosion behaviour of Trichoderma harzianum for AZ31B magnesium alloy in artificial seawater, Corros. Sci. 118 (2017) 12-23. [75] C. Verma, M.A. Quraishi, E.E. Ebenso, I.B. Obot, A. El Assyry, 3-Amino alkylated indoles as corrosion inhibitors for mild steel in 1 M HCl: Experimental and theoretical studies, J. Mol. Liq. 219 (2016) 647-660. 43

[76] C. Verma, P. Singh, I. Bahadur, E.E. Ebenso, M.A. Quraishi, Electrochemical, thermodynamic, surface and theoretical investigation of 2-aminobenzene-1,3-dicarbonitriles as green corrosion inhibitor for aluminum in 0.5 M NaOH, J. Mol. Liq. 209 (2015) 767-778. [77] Sudheer, M.A. Quraishi, Electrochemical and theoretical investigation of triazole derivatives on corrosion inhibition behavior of copper in hydrochloric acid medium, Corros. Sci. 70 (2013) 161-169. [78] M.A. Deyab, Corrosion inhibition of heat exchanger tubing material (titanium) in MSF desalination plants in acid cleaning solution using aromatic nitro compounds, Desalination 439 (2018) 73-79. [79] D.S. Chauhan, K.R. Ansari, A.A. Sorour, M.A. Quraishi, H. Lgaz, R. Salghi, Thiosemicarbazide and thiocarbohydrazide functionalized chitosan as ecofriendly corrosion inhibitors for carbon steel in hydrochloric acid solution, Int. J. Biol. Macromol. 107 (2018) 1747-1757. [80] M. Mobin, M. Basik, J. Aslam, Boswellia serrata gum as highly efficient and sustainable corrosion inhibitor for low carbon steel in 1 M HCl solution: Experimental and DFT studies, J.Mol. Liq. 263 (2018) 174-186. [81] M.A. Hegazy, A.M. Badawi, S.S. Abd El Rehim, W.M. Kamel, Corrosion inhibition of carbon steel using novel N-(2-(2-mercaptoacetoxy)ethyl)-N,N-dimethyl dodecan-1-aminium bromide during acid pickling, Corros. Sci. 69 (2013) 110-122. [82] J. Zhang, Z. Liu, G.-C. Han, S.-L. Chen, Z. Chen, Inhibition of copper corrosion by the formation of Schiff base self-assembled monolayers, Appl. Surf. Sci. 389 (2016) 601-608. [83] G.L.F. Mendonça, S.N. Costa, V.N. Freire, P.N.S. Casciano, A.N. Correia, P.d. Lima-Neto, Understanding the corrosion inhibition of carbon steel and copper in sulphuric acid medium by amino acids using electrochemical techniques allied to molecular modelling methods, Corros. Sci. 115 (2017) 44

41-55.

[84] I.B. Obot, N.O. Obi-Egbedi, E.E. Ebenso, A.S. Afolabi, E.E. Oguzie, Experimental, quantum chemical calculations, and molecular dynamic simulations insight into the corrosion inhibition properties of 2-(6-methylpyridin-2-yl)oxazolo[5,4-f][1,10]phenanthroline on mild steel, Res. Chem. Intermediat. 39 (2013) 1927-1948.

Highlights ●

Ionic polymers containing multiple N-heterocycles were synthesized.

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Self-assembly ionic polymer aggregates were obtained in aqueous sulfuric acid solution.

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Chemical adsorption of the ionic polymer aggregates on copper was investigated.

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Copper corrosion inhibition by the ionic polymer aggregates in acid medium was demonstrated

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