Electrochemical polymerization process and excellent electrochromic properties of ferrocene-functionalized polytriphenylamine derivative

Accepted Manuscript Electrochemical polymerization process and excellent electrochromic properties of ferrocene-functionalized polytriphenylamine derivative Xiaojing Lv, Conghui Huang, Alexey Tameev, Liang Qian, Rui Zhu, Konstantin Katin, Mikhail Maslov, Alexander Nekrasov, Cheng Zhang PII:

S0143-7208(18)31949-1

DOI:

https://doi.org/10.1016/j.dyepig.2018.12.019

Reference:

DYPI 7224

To appear in:

Dyes and Pigments

Received Date: 4 September 2018 Revised Date:

7 December 2018

Accepted Date: 12 December 2018

Please cite this article as: Lv X, Huang C, Tameev A, Qian L, Zhu R, Katin K, Maslov M, Nekrasov A, Zhang C, Electrochemical polymerization process and excellent electrochromic properties of ferrocenefunctionalized polytriphenylamine derivative, Dyes and Pigments (2019), doi: https://doi.org/10.1016/ j.dyepig.2018.12.019. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT

Electrochemical polymerization process and excellent electrochromic properties of ferrocene-functionalized polytriphenylamine derivative Xiaojing Lv,a Conghui Huang,a Alexey Tameev,b Liang Qian,a Rui Zhu,a Konstantin

a

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Katin,c Mikhail Maslov,c Alexander Nekrasov,b and Cheng Zhang*a International Sci. & Tech. Cooperation Base of Energy Materials and Application,

310014, P. R. China

The laboratory for Electronic and Photonic Processes in Polymer Nanocomposites,

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b

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College of Chemical Engineering, Zhejiang University of Technology, Hangzhou

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, Moscow 119071, Russia c

Nanoengineering in Electronics, Spintronics and Photonics Institute, National

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Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow 115409, Russia

Abstract

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*E-mail: [email protected]

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A novel triphenylamine (TPA) derivative (E)-N-(4-(Diphenylamino)phenyl)formimidoylferrocene) (TPAFc) containing ferrocene (Fc) unit was designed and synthesized successfully. Theoretical calculation and experimental data show TPAFc possesses higher HOMO energy level and the lower onset oxidative potential compared to TPA monomer. Cyclic voltammetry test demonstrates coupling reaction between TPA units and the formation of an electroactive polymer film during successive scans. This intriguing phenomenon may be ascribed to the multi-step 1

ACCEPTED MANUSCRIPT oxidation process and Fc unit plays an important role as charge transport center for electrons moving from TPA units and the surface of the forming oligomer film to the electrode. SEM images indicate PTPAFc film shows the surface morphology of

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uniform tubular structures, which may largely increase the area of interface between the electrolyte solution and the polymer film. Interestingly, PTPAFc film exhibits reversible multicolor changes switched from neutral transparent color to light orange

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and blue in fully oxidized state, which are attributed to that the existence of Fc unit

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brings out multiple redox states. In addition, the polymer film presents excellent electrochromic performances in the aspect of high optical contrast (~58%), good coloration efficiency (~130 cm2·C-1) and fast switching time (~2 s). In view of these excellent features, the developed PTPA derivative is very satisfactory for applications

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on high-performance electrochromic devices.

Keywords: triphenylamine; electropolymerization; ferrocene; multi-step oxidation; electrochromic

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1. Introduction

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Electrochromic (EC) materials have been studied extensively owing to their huge potential applications on smart windows, rear-view mirror, sunglasses, displays, memory device and sensors. [1-6] Early studies mainly concentrated on inorganic transition metal oxides (for instance WO3, NiO) [7] and organic small molecule (like viologen) [8]. Compared to those materials, conjugated polymers have recently attracted increasing interests owing to their superior advantages, such as easy processability, tunable color-showing, good coloration efficiency and optical contrast, 2

ACCEPTED MANUSCRIPT fast switching capabilities. [9-13] Triphenylamine (TPA) derivatives are good electron donors and hole transport materials, which have been widely applied to organic optoelectronic devices. [14-15]

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Polytriphenylamine (PTPA) and its derivatives as the typical electrochromic materials, possess various advantages in terms of low oxidation potential, protonic acid doping easily, high optical contrast and good environmental stability. [16-17] To date, Liou et

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al. [18], Niu et al. [19], Zhao et al. [20], Xu et al. [21] and Hsiao et al. [22]

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synthesized various PTPA derivatives via chemical polymerization route and investigated their electrochromic properties. However, it is still difficult for TPA derivatives to obtain corresponding polymers by electrochemical polymerization method. The main reason is that TPA monomer is easily oxidized to form the cationic

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radical TPA+•, while the cationic radical is unstable and undergo rapid coupling reaction, thus losing two protons to produce tetraphenylbenzidine (TPB); TPB is more likely to be oxidized than TPA, which loses one electron to form TPB+•, and then

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loses another electron to become TPB2+, thereby hindering further electrochemical

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polymerization.[23] The electrochemical oxidation process of TPA monomer is shown in Scheme 1.

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Scheme 1 Electrochemical oxidation process of TPA monomer.

Initial researches have shown that the introduction of electron-donating groups

cationic

radicals

and

thus

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such as pyrrole, carbazole and thiophene on the para-position of TPA can stabilize the obtain

corresponding

polymer

films

by

electropolymerization method. For example, Plater et al. [24] electrochemically synthesized poly(N-[4-(N’,N’-Diphenylamino)]phenylpyrrole) by introducing pyrrole

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unit into TPA monomer. Hsiao et al. [25] and Zhang et al. [26] prepared poly(4-(9H-carbazol-9-yl)-N,N-diphenylaniline) with the introduction of carbazole

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unit at the para-position of TPA by electrochemical polymerization route. Zhao et al. [20] and Zhang et al. [27] synthesized TPA derivatives (TTPA and TBTPA) by

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modifying thiophene or bithiophene units into the para-positions of TPA and successfully prepare their polymers through electrochemical polymerization. However, these introduced electron-donating groups like pyrrole, carbazole and thiophene are inherently capable of redox activity and electropolymerization reaction can also occur at these sites. Therefore, it is difficult to clearly determine the exact structure of these polymers and whether the TPA unit or these substituted units undergo coupling polymerization to form polymer films, which further brings out uncertainty and 4

ACCEPTED MANUSCRIPT complexity for the investigating the electrochemical and electrochromic performance of PTPA derivatives. Ferrocene (Fc) is widely used as an organometallic functional group owing to

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good stability, easy modification and excellent electron-donating character. In recent years, many research groups have reported Fc functionalized conjugated polymers based on pyrrole [28], thiophene [29] as well as carbazole [30] systems, and most of

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them showed good electrochromic properties. Moreover, Fc is a stable

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electron-donating group and possesses a single electron reversible redox reaction of Fc+/Fc that does not undergo electrochemical coupling reaction. Herein, a novel monomer TPAFc through introducing Fc unit at the para-position of TPA was designed and synthesized by convenient synthetic route. Due to the strong electron

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rich character and excellent oxidation–reduction reversibility of Fc, it may play a role as charge transport center for electrons moving from TPA units and the surface of the forming oligomer film to the electrode, further leading to the deposit of polymer films

Fc-functionalized

polytriphenylamine

derivative

(PTPAFc)

was

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Hence,

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on the electrode.

successfully prepared in this work through electropolymerization route for the first time. The effect of Fc for TPAFc monomer on the electrochemical polymerization process was studied and clarified herein. The electrochromic and electrochemical characters of PTPAFc were investigated in details. This work would be helpful to have a better understanding on the electropolymerization process of TPA derivatives and may provide great experience for designing and preparation of novel 5

ACCEPTED MANUSCRIPT polytriphenylamine derivatives with excellent electrochromic performance via electropolymerization route. 2. Experimental section

N,N-diphenyl-p-phenylenediamine (98%),

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2.1 Materials ferrocenecarboxaldehyde (98%),

basic aluminium oxide (100-200 mesh), tetrabutylammonium perchlorate (TBAP,

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98%) were purchased from Aladdin used as received without further purification. All

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other solvents and reagents were analytical reagent. Indium tin oxide (ITO) glass substrates (Kaivo Optoelectronic Technology Co., Ltd., Rs ≤ 10 Ω □–1) were used after strictly ultrasonic washing in ethanol, distilled water, acetone and toluene solutions, respectively.

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2.2 Characterization

H-NMR spectra of TPAFc monomer was recorded by Bruker AVANCE III

instrument (Bruker, Switzerland). Mass spectra (MS) was tested by AXIMA-CFRTM

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plus instrument. Fourier Transform Infrared (FT-IR) spectra was recorded on a

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Nicolet 6700 spectrometer (Thermo Fisher Nicolet, USA) with KBr pellets. Surface and cross-sectional morphologies of PTPAFc polymer film were performed by Scanning electron microscopy (SEM, NOVA NANOSEM 450). The electrochemical behaviors of monomers and polymer films were carried out in three-electrode cells with a CHI 660E electrochemical workstation in a 0.1 M TBAP/dichloromethane (DCM) solution. All the electrochemical characterizations were carried out under room temperature. Electrochromic properties and spectroelectrochemistry were tested 6

ACCEPTED MANUSCRIPT by CHI660E electrochemical worksation combined with Shimadzu UV-1800 UV-Vis spectrophotometer (Shimadzu, Japan). Chromaticity coordinate data was collected in Japan Konica Minolta spectrophotometer CM-3600d. The GAMESS program was

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used for computing parameters of the molecules. The theoretical computations of frontier molecular orbitals as well as the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels were based on

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restricted density functional theory (DFT) and were completed by using Becke’s

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three-parameter hybrid method and the Lee-Yang-Parr exchange-correlation energy functional (B3LYP) [31, 32] with the 6-31G(d) basis set for all elements considered. 2.3 Synthesis of (E)-N-(4-(Diphenylamino)phenyl)formimidoylferrocene)(TPAFc) 4-aminotriphenylamine (0.2097 g, 1 mmol), ferrocene formaldehyde (0.2654 g,

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1.2 mmol), basic aluminum oxide (1.0159 g, 0.98 mmol) was added in a previously dried two-necked flask. Xylene (50 ml) was then added the above solution and stirred as the temperature up to 100℃. Then the reaction was refluxed under nitrogen

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atmosphere for 10 h. After that, the residual solution was removed by filtration to give

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a solid crude product. The crude product was washed with ethanol and dried to obtain the final red solid powder TPAFc (0.3206 g) with a yield of 70.28%. 1H NMR (400 MHz, DMSO-d6): δ 8.44 (s, 1H), 7.30 (t, J = 7.7 Hz, 4H), 7.22-7.14 (m, 3H), 7.02 (d, J = 10.7, 7.6 Hz, 8H), 4.91-4.68 (m, 2H), 4.65-4.46 (m, 2H), 4.26 (s, 5H). MS (EI): m/z =456.2 (M+). FT-IR：1620 cm-1, 1587 cm-1, 1489 cm-1, 1273 cm-1, 1319 cm-1, 1188 cm-1, 1107 cm-1, 827 cm-1, 493 cm-1.The data of 1H NMR, MS, and FT-IR are

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ACCEPTED MANUSCRIPT shown in Fig.S1, Fig. S2, Fig. S3. The chemical structure and synthesis route of

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TPAFc are summarized in Scheme 2.

Scheme 2 Chemical structure and synthesis route of TPAFc.

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2.4 Preparation of poly-(E)-N-(4-(Diphenylamino)phenyl) formimidoyl ferrocene) (PTPAFc)

The PTPAFc film was fabricated via potentiostatic polymerization method in a conventional three-electrode cell with 2 mM TPAFc and 0.1 M TBAP/DCM as the

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electrolyte solution. The ITO glass, platinum wire and Ag/AgCl electrode (silver wire coated with AgCl in saturated KCl solution) were used as the working electrode, the

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auxiliary electrode and the reference electrode, respectively. The polymerization potential was 1.4 V and the polymerization charge was 0.3 C. Then the polymer film

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was dedoped in 0.1 M TBAP/DCM and finally washed with DCM solvents. 3. Results and Discussion 3.1 Electrochemical behavior of TPAFc monomer In order to study the effect of introducing Fc unit on the electrochemical performance of TPAFc, the cyclic voltammetry characteristics of the monomers TPA, Fc and TPAFc were carried out by using glassy carbon electrode as the working electrode. Fig. 1 shows the cyclic voltammogram of 2 mM TPA, 2 mM TPAFc, 2 8

ACCEPTED MANUSCRIPT mM Fc monomers in 0.1 M TBAP/DCM solutions at scan rate of 100 mV·s-1. TPA exhibits the oxidation peak of about 1.30 V and two reduction peaks of about 0.97 V and 0.76 V with an onset oxidation potential located at 0.98 V. Fc presents one pair of

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quasi-reversible redox peaks at about 0.64 V and 0.42 V with one onset oxidation potential of 0.46 V. For TPAFc, it exhibits three couples of redox peaks at 1.29 V, 1.10 V, 0.76 V and two reduction peaks at 0.95 V, 0.78 V, 0.62 V, indicating that it

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undergoes multi-step oxidation and reduction process. Among them, the first couple

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of redox peaks at 0.76 V and 0.62 V should belong to the single electron reversible redox peak of Fc+/Fc. The following redox potential peaks are belonging to charge transport and cationic radical reaction of TPA during the electrochemical process. Moreover, TPAFc shows a lower onset oxidation potential at 0.49 V compared to that

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of TPA, which is also attributed to the introduction of Fc unit.

Fig. 1 Cyclic voltammogram of 2 mM TPA, 2 mM TPAFc, 2 mM Fc in 0.1 M TBAP/ DCM solutions at the scan rate of 100 mV·s-1 using glassy carbon electrode. 9

ACCEPTED MANUSCRIPT Fig. 2 shows the subsequent cyclic voltammetry curves of 2 mM TPAFc monomer in 0.1 M TBAP/DCM solution from 0 V to 1.4 V using platinum sheet as the working electrode. It can be found that both oxidation and reduction peaks located

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at 1.17 V and 0.89 V gradually increase during successive scans (from Fig. S4), which indicates coupling reaction between TPA units and the formation of electroactive polymer films. In addition, it could be observed that a dark brown

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polymer film deposited on the surface of the ITO glass. This result implies that the

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introduction of Fc unit at the para-position of TPA can be helpful for TPAFc

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monomer to obtain its corresponding polymer film by electropolymerization method.

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Fig. 2 Successive cyclic voltammogram curve of 2 mM TPAFc monomer in 0.1 M TBAP/DCM solution using platinum sheet as the working electrode. 3.2 Theoretical calculations In order to further studies on the electronic character, the energy level and electron density distribution of TPAFc are shown in Fig. 3. TPAFc shows the HOMO energy level of -4.77 eV which mainly belong to the TPA unit and Fc unit, and the LUMO energy level of -0.92eV mainly belong to the C=N unit. While TPA shows the 10

ACCEPTED MANUSCRIPT HOMO energy level of -4.95 eV and the LUMO energy level of -0.30 eV and Fc shows the HOMO energy level of -5.13 eV and the LUMO energy level of 0.22 eV according to the reported work [33-35]. Thus, the introduction of Fc unit may greatly

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increase the electronic cloud density around the TPA unit, which may result in the more stable cationic radicals during the electrochemical process. Moreover, the theoretical calculation results further demonstrate that TPAFc with the higher HOMO

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energy level leads to the lower onset oxidative potential, which is consistent with the

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data revealed by cyclic voltammetry curves shown in Fig. 1. All the experimental and

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theoretical calculation data are shown in the Table 1.

Fig. 3 (a) Optimized conformations and (b) calculated spatial electron distributions of HOMO and LUMO for TPAFc (the value of the contour envelopes is 0.03 a.u.).

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Table 1 Experimental and theoretical calculation data for TPAFc and TPA. Theoretical Calculations Epa

onset

Epc

λonset

monomer (V)

(V)

(V)

EHOMO

ELUMO

(eV)

(eV)

(nm)

0.49

0.76;1.10;1.29

0.62;0.78;0.95

551

-4.77

-0.92

TPA

0.98

1.30

0.76;0.97

336

-4.95

-0.30

Fc

0.46

0.64

0.42

522

-5.13

Eg

E'HOMOb

E'LUMOc

(eV)

(eV)

(eV)

3.85

-4.76

-2.51

2.25

4.65

-5.25

-1.56

3.69

4.91

-4.80

-2.42

2.38

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0.22

a

UV-Vis spectra of TPAFc, TPA and Fc are shown in Fig. S5;

b

E'HOMO= -4.8eV- e×(Eoxonset-E1/2-Ferrocene);

c

E'LUMO= Eg+ E'HOMO;

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Eg= 1240 / λonset

E'gd

(eV)

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TPAFc

d

Experimental Calculations

a

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E

ox

3.3 Electropolymerization process analysis of PTPAFc Combined with the electrochemical characterization and theoretical calculations,

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the possible electropolymerization process of TPAFc is put forward as shown in

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Scheme 3. Under the positive voltage, Fc unit is firstly oxidized and loses one electron to form the Fc+ cation (1). As the applied potential increasing, TPA unit is further oxidized to form the cationic radical (2). With the p-electron delocalization around the terminal TPA backbone, the resonated quinoid structures (3) would be formed. [36] Then two of cationic radical (3) undergo coupling reaction (4) with losing two protons to produce cationic oligomerizer (5). Next, one of TPA unit for (5) continues to be oxidized to form the stable cationic radical (6), which cannot be 12

ACCEPTED MANUSCRIPT oxidized and loses another electron due to the existence of Fc+. Thus, two of cationic radical (6) undergo coupling reaction and lose two protons to produce another cationic oligomerizer (7). Thus, it would repeat the similar redox processes (5)~(7) and finally

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to form polymer PTPAFc after dedoping. Therefore, it is the key factor to involve multi-step oxidation reaction for the electrochemical polymerization of TPAFc monomer. During the polymerization process, the Fc unit plays an important role as

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charge transport center for electrons moving from TPA units and the surface of the

on the electrode. 3.4 Electrochemistry of PTPAFc

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forming oligomer film to the electrode, further leading to the deposit of polymer films

Fig. 4 exhibits cyclic voltammograms of PTPAFc film in 0.1 M TBAP/DCM

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solution at different scan rates (20, 25, 50, 75, 100, 125, 150, 175, 200 mV·s-1). The polymer film exhibits three couple of reversible redox peaks (0.70 V and 0.60 V, 0.91 V and 0.78 V, 1.14 V and 0.98 V) at scan rate of 20 mV/s, which are assigned to the

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single electron reversible redox peak of Fc+/Fc, charge transfer and cationic radical

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reaction of TPA, respectively. Meanwhile, the peak current of the polymer film increases with the increasing scan rate, indicating that the polymer film adhered on the ITO surface has good electrochemical activity. Fig. 4b shows good linear dependence between the peaks current and scan rate, which demonstrates that the electrochemical process of PTPAFc is reversible and the charge transfer across the polymer film is not restricted by diffusion of counterions [37].

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Scheme 3 Electropolymerization process analysis of PTPAFc. 14

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Fig. 4 (a) Cyclic voltammograms of PTPAFc film at different scan rates in 0.1 M

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TBAP/DCM solution; (b) Scan rate dependence of the anodic and cathodic peak

3.5 The morphology of polymer film

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current.

Fig. 5 shows the SEM images for PTPAFc film of the surface and cross-sectional. It can be seen that the surface of the polymer film consists of uniform tubular

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structures. Fig. 5c reveals that PTPAFc film partly consists of a thin layer of about 120 nm (marked by a red dashed line) and tubular structures with diameters in the range of hundreds of nanometers above the thin layer. The presence of these tubular

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structures may result in a higher surface contact area between the electrolyte solution

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and the polymer film, thus rendering much easier doping of counterions and better electrochromic properties.

Fig. 5 SEM images of PTPAFc film: (a, b) Surface morphology; (c) cross-sectional morphology. 15

ACCEPTED MANUSCRIPT 3.6 Spectroelectrochemical behavior Spectroelectrochemistry is a common method for researching the optical changes in the absorption spectra and provides the insights into the electronic structure of

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conjugated polymers as applied potentials. [38] Fig. 6 exhibits the UV-vis absorption spectra of PTPAFc film under different potentials. At 0 V, a clear absorption band appears at 350 nm, which belong to the π-π* transition of the polymer backbone.

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Besides, there is a weak absorption peak located at 400~500 nm, which can be

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ascribed to the charge transfer transition between the Fe(II) and cyclopentene. [39] With increasing the applied potential, the intensity of these peaks decrease gradually, accompanied with the appearance of charge carrier bands at round 475 nm, 800 and 1100 nm that arises from the evolution of polaron and bipolaron bands and the doping

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of counterions. [40, 41] Meanwhile, the polymer film presents from neutral transparent (L*, a*, b*: -0.12, -2.05, -5.21) state to the light orange color (L*, a*, b*: 2.67, -7.47, -9.91) and blue color (L*, a*, b*: 6.56, -18.14, -17.38) in the oxidized state.

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The chromaticity coordinate of PTPAFc film is shown in Fig. S6. This multi-colored

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electrochromism should be ascribed to that the introduction of Fc group brings out more redox states under applied different potentials.

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Fig. 6 Spectroelectrochemical behavior of PTPAFc film on the ITO glass under different applied potentials in 0.1 M TBAP/DCM solution (Inset: color showing at 0 V, 1V and 1.2 V). 3.7 Electrochromic performance

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The electrochromic switching character of PTPAFc film was examined from 300 nm to 1100 nm between 0 and 1.4V with residence time of 5s and 10s. From Fig. 7, the polymer film displays high optical contrasts of 58.85% (5 s), 58.54% (10 s) at 800

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nm and 25.25% (5 s), 29.49% (10 s) at 1100 nm between its oxidized and neutral

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states. Moreover, it can be seen that optical contrasts of the polymer film has no obvious variation as the switch time increases from 5 s to 10 s. The switching time is defined as the time required to achieve 95% of its complete transmittance changes between different potentials. According to Fig. 8, the polymer film has reasonable switching time of 2.084 s (colored time) and 2.179 s (bleached time) at 800 nm, 0.737 s (colored time) and 2.224 s (bleached time) at 1100 nm. In addition, the coloration efficiency (CE) is also an important parameter for the electrochromic materials, which 17

ACCEPTED MANUSCRIPT is illustrated by equation: CE = ∆OD/Qd.. Qd represents the injected charge density as a function of electrode area that can be stated for 95% of the full optical switch, which was investigated via chronocoulometry experiments (in Fig. S7). ∆OD can be

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obtained from the equation: ∆OD = log(Tbleached /Tcolored), Tcolored and Tbleached are the transmittance values in the oxidized and neutral states, respectively. [30, 42, 43] The CE values of PTPAFc film are calculated to be 127.41 cm2·C-1 (5s) and 132.83

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cm2·C-1 (10s) at 800 nm, respectively. All the data of electrochromic properties for

via

electrochemical

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PTPAFc film are shown in Table 2. The results show that the obtained PTPAFc film polymerization

route

exhibits

excellent

electrochromic

performance, such as reasonable switching time, high optical contrast and good coloration efficiency, which is expected to show potential applications on

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electrochromic devices.

Fig. 7 Optical contrasts of PTPAFc film monitored at 800 nm and 1100 nm in 0.1 M TBAP/DCM solution between 0 and 1.4 V with a residence time of 5 s and 10 s.

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Fig. 8 Electrochromic switching response for PTPAFc film monitored at 800 nm

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and1100 nm in 0.1 M TBAP/DCM solution between 0 and 1.4 V with a residence

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time of 5s.

Table 2 All the electrochromic properties of PTPAFc film. Polymer

Color display

0V:

Optical contrast

transparent

800nm:

1V:

58.85% (5s),

light orange

PTPAFc

tb=2.179 1100nm: 1100nm:

1100nm:

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tc=2.084,

50.24

blue

25.25% (5s),

tc=0.737,

(L*,a*, b*: 6.56,-18.14,-17.38)

29.49% (10s)

tb=2.224

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1.2V:

800nm:

127.41

58.54% (10s)

(L*,a*, b*: 2.67,-7.47,-9.91)

CE (cm2·C-1)

800nm:

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(L*,a*, b*: -0.12,-2.05,-5.21)

Switching time (s)

4. Conclusions

In this work, a novel ferrocene functionalized triphenylamine derivative (TPAFc)

was designed and synthesized through introducing Fc unit at the para-position of TPA. Theoretical calculation and cyclic voltammetry results demonstrate that TPAFc with higher HOMO energy level leads to the lower onset oxidative potential. Its corresponding

polymer

PTPAFc

could

be

successfully

obtained

through 19

ACCEPTED MANUSCRIPT electropolymerization method. This intriguing phenomenon may be ascribed to the multi-step oxidation process due to the existence of Fc unit and it plays an important role as charge transport center for electrons moving from TPA units and the surface of

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the forming oligomer film to the electrode, further leading to the deposit of polymer films on the electrode. SEM images show that PTPAFc polymer film has the surface morphology of uniform tubular structures, which may largely increase the contact

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area between the electrolyte solution and the polymer film. Thereby, PTPAFc polymer

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film exhibits reversible color changes between neutral transparent color, light orange and blue in fully oxidized state, excellent electrochromic characteristics in term of good coloration efficiency, high optical contrast and fast switching respond. In view of the excellent features, the PTPAFc film can be used as a promising candidate for

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the application of EC devices. In summary, the significant contribution in this study is to provide theoretical and experimental basis on the designing and synthesis of novel PTPA

derivatives

with

excellent

electrochromic

performance

via

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electropolymerization route.

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Acknowledgements

The authors gratefully thank the support from National Natural Science

Foundation of China (51703199, 51673174), Natural Science Foundation of Zhejiang Province, China (LZ17E030001) and New-shoot Talents Plan of Zhejiang province (2018R403055, 2018R403091). Appendix A. Supplementary information

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[4] T. N. Wei, Q. Ye, S. J. Chua, J. Xu, Conjugated polymer-based electrochromics: materials, device fabrication and application prospects, J. Mater. Chem. C 4 (2016) 7364-7376.

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Supporting Information

Electrochemical polymerization process and excellent electrochromic

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properties of ferrocene-functionalized polytriphenylamine derivative Xiaojing Lv,a Conghui Huang,a Alexey Tameev,b Liang Qian,a Rui Zhu,a Konstantin

a

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Katin,c Mikhail Maslov,c Alexander Nekrasov,b and Cheng Zhang*a

International Sci. & Tech. Cooperation Base of Energy Materials and Application,

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College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, P. R. China b

The laboratory for Electronic and Photonic Processes in Polymer Nanocomposites,

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A.N. Frumkin Institute of Physical Chemistry and Electrochemistryof the Russian Academy of Sciences, Moscow 119071, Russia

Nanoengineering in Electronics, Spintronics and Photonics Institute, National

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c

Research Nuclear UniversityMEPhI (Moscow Engineering Physics Institute), Moscow

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115409, Russia

Corresponding Author *E-mail: [email protected]

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Fig. S1 1H NMR spectra of TPAFc in DMSO-d6.

x10 5 +ESI Scan (0.1-0.1 min, 3 scans) Frag=175.0V JSTPAFC.d Subtract (2) 457.1

7.5

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7 6.5 6 5.5

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5 4.5 4

3.5 3

2.5 2

1.5 1 0.5 0

100

150

200

250

300

350

400 450 500 550 600 Counts vs. Mass-to-Charge (m/ z)

650

700

750

800

850

900

Fig. S2 Mass spectra of TPAFc.

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Fig. S3 FT-IR spectra of TPAFc.

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Fig. S4 The plots of peak current Ip vs cycles.

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Fig. S5 The UV-vis spectra of TPAFc, TPA and Fc.

Fig. S6 The Chromaticity coordinate of PTPAFc film at 0V, 1.0V, 1.2 V.

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1100nm with a residence time of 5s.

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Fig. S7 The chronocoulometry experiments for PTPAFc film monitored at 800 and

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ACCEPTED MANUSCRIPT Highlights •

A novel triphenylamine derivative containing ferrocene unit was designed and synthesized.

the formation of an electroactive polymer film.

The polymer film exhibits reversible multicolor changes, high optical contrast,

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good coloration efficiency and fast switching time.

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•

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Cyclic voltammetry demonstrates the coupling reaction between TPA units and

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•