Supporting Information for. Recombination Strategy for Processable Ambipolar Electroactive Polymers. in Pseudocapacitors

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1 Supporting Information for Recombination Strategy for Processable Ambipolar Electroactive Polymers in Pseudocapacitors Yilin Wang,, Weishuo Li,, Yitong Guo, Jupeng Cao, Imran Murtaza, Ahmed Shuja Syed, Yaowu He *, and Hong Meng *, These authors contributed equally to this work. School of Advanced Materials, Peking University Shenzhen Graduate School, Peking University, Shenzhen , China. Department of Physics, International Islamic University, Islamabad 44000, Pakistan. Centre for Advanced Electronics & Photovoltaic Engineering (CAEPE), International Islamic University, Islamabad 44000, Pakistan. Contents: S1. General instrumentation... 2 S2. Procedures of monomer and polymer synthesis... 2 S3. Film formation S4. Spectroelectrochemistry of PEBE, PPBP, PEBE-PBP and PEB-P S5. Specific capacitance calculation S6. Capacitance and stability of PEBE-PBP and PEB-P with literature S7. Stability test of PEBE-PBP, PEB-P and PEBE in p-doped state S8. EIS test of PEBE-PBP and PEB-P at oxidized, neutral and reduced states S9. SEM image of PEBE-PBP and PEB-P polymer films on ITO-coated glass slides References

2 S1. General instrumentation 1 H NMR spectra were recorded using Bruker Avance 500,Bruker Avance 400 and Avance-III NMR spectrometers, with chloroform-d as the solvent as the internal standard. High-resolution mass spectra (HRMS) were recorded using an ABI Qstar Elite spectrometer, with the dichloromethane (DCM) as the solvent. Average molecular weights and polydispersity indices (PDIs) were measured through gel permeation chromatography (GPC; Waters 1515_2414). FT-IR spectra were measured using a PerkinElmer Spectrum 2 transform infrared spectrometer with liquid and solid (KBr as reference) method. S2. Procedures of monomer and polymer synthesis All monomers and structures before monomers were synthesized in satisfactory yields and well characterized as previously reported (Scheme S1-S4). 1-4 S2.1 Synthesis of PEBE Scheme S1. Synthesis of PEBE EBE: The obtained EBE was dried in vacuum and isolated as a deep red solid (1.264 g, 76%). 1 H NMR spectrum is same as the reported one. 5 1 H NMR (300 MHz, CDCl 3 ) δ 8.41 (s, 2H), 6.58 (s, 2H), 4.42 (d, J = 2.7 Hz, 4H), (m, 4H). 2

3 Figure S1. 1 H NMR of EBE (solvent: chloroform-d). PEBE: This polymer was obtained using electrochemical polymerization. Detailed parameters were listed in the following film formation part (Section S3.1). S2.2 Synthesis of PPBP According to previously reported procedures, 6 ProDOT, the monomer PBP and polymer PPBP were prepared in satisfactory yields (Scheme S2). Scheme S2. Synthesis of PPBP 3

4 ProDOT: Yield: 2.31 g (80 %). 1 H NMR (400 MHz, CDCl 3 ) δ 6.44 (s, 2H), 4.01 (s, 4H), 3.48 (s, 4H), 3.40 (t, J = 6.5 Hz, 4H), 1.53 (m, 6.6 Hz, 4H), (m, 12H), 0.89 (t, J = 6.9 Hz, 6H). Figure S2. 1 H NMR of ProDOT (solvent: chloroform-d). PBP: Yield: 2.46 g (64 %). 1 H NMR (500 MHz, CDCl 3 ) δ 8.29 (s, 2H), 6.67 (s, 2H), 4.22 (s, 4H), 4.11 (s, 4H), 3.57 (s, 8H), 3.44 (t, J = 6.5 Hz, 8H), (m, 8H), 1.32 (m, 5.7 Hz, 24H), 0.90 (t, J = 6.8 Hz, 12H). PPBP: Yield: 0.35 g (84 %). 1 H NMR (400 MHz, CDCl 3 ) δ 8.37 (br s, 2H), 4.32 (br s, 8H), (br, 16H), 1.61 (br s, 8H), 1.34 (br s, 24H), 0.91 (br s, 12H). GPC analysis: M n = 14.2 kda; M w = 17.3 kda; PDI:

5 Figure S3. 1 H NMR of PBP (solvent: chloroform-d). Figure S4. 1 H NMR of PPBP (solvent: chloroform-d). 5

6 S2.3 Synthesis of PEBE-PBP Scheme S3. Synthesis of PEBE-PBP BrPBPBr: The dark red oil was obtained (0.25 g, 88%). 1 H NMR (500 MHz, CDCl 3 ) δ 8.30 (s, 2H), 4.22 (s, 4H), 4.17 (s, 4H), 3.56 (d, J = 3.0 Hz, 8H), 3.43 (t, J = 6.5 Hz, 8H), (m, 8H), 1.31 (m, 24H), 0.89 (s, 12H). Figure S5. 1 H NMR of BrPBPBr (solvent: chloroform-d). 6

7 PEBE-PBP: To a 25 ml round bottom flask with stir bar, the solution of EBE (62.4 mg, 0.15 mmol), BrPBPBr (158.9 mg, 0.15 mmol) and K 2 CO 3 (52.3 mg, 0.30 mmol), pivalic acid (4.60 mg, mmol) in DMAc (15 ml) was added and purified with N 2 for 15min. After adding Pd(OAc) 2 (1.35 mg, mmol), the solution was stirred at 140 C under N 2 for 24 h. After the flask was removed from oil bath and allowed to cool to r.t., the product was precipitated in methanol. The precipitate was filtered into a Soxhlet extraction thimble and washed sequentially with hot methanol, acetone, hexanes, chloroform and chlorobenzene. The washings were conducted until color was no longer observed during extraction. Polymer used for property test was isolated by concentrating the polymer part dissolved in chlorobenzene. The concentrated polymer was filtered and dried under vacuum. Yields and GPC analyses has been listed in Table S1. 1 H NMR (300 MHz, CDCl 3 ) δ 8.41 (br s, 4H), (br m, 32H), (br m, 32H), 0.91 (br s, 12H). Figure S6. 1 H NMR of PEBE-PBP (solvent: chloroform-d). 7

8 Figure S7. FT-IR of EBE (black line), BrPBPBr (red line) and PEBE-PBP (blue line). S2.4 Synthesis of PEB-P Scheme S4. Synthesis of PEB-P. BrEBBr: Yield: 0.57 g (94 %). 1 H NMR (500 MHz, CDCl 3 ) δ 8.21 (d, J = 7.9 Hz, 1H), 7.83 (d, J = 7.9 Hz, 1H), (m, 2H), (m, 2H). HRMS (DART) m/z: MS:[M + H] + calcd for C 12 H 8 N 2 O 2 S 2 Br ; found

9 Figure S8. 1 H NMR of BrEBBr (solvent: chloroform-d). Figure S9. HRMS of BrEBBr (solvent: DCM). PEB-P: To a 50 ml round bottom flask with stir bar, the solution of BrEBBr (130.2 mg, 0.30 mmol), ProDOT (142.1 mg, 0.30 mmol), and K 2 CO 3 (104.6 mg, 0.60 mmol), pivalic acid (9.2 mg, 9

10 0.090 mmol) in DMAc (30 ml) was added and purified with N 2 for 15 min. After adding Pd(OAc) 2 (2.70 mg, mmol), the solution was stirred at 140 C under N 2 for 24 h. After the flask was removed from oil bath and allowed to cool to r.t., the product was precipitated in methanol. The precipitate was filtered into a Soxhlet extraction thimble and washed sequentially with hot methanol, acetone, hexanes, chloroform and chlorobenzene. The washings were conducted until color was no longer observed during extraction. Polymer used for property test was isolated by concentrating the polymer part dissolved in chlorobenzene. The concentrated polymer was filtered over a filter paper and collected into a tared vial for drying under vacuum. The concentrated polymer was filtered and dried under vacuum. Yields and GPC analyses has been listed in Table S1. 1 H NMR (300 MHz, CDCl 3 ) δ 8.45 (br s, 4H), (br m, 32H), (br m, 32H), (br m, 12H). Figure S10. 1 H NMR of PEB-P (solvent: chloroform-d). 10

11 Figure S11. FT-IR of BrEBBr (black line), ProDOT (red line) and PEB-P (blue line). Table S1. Yields and GPC analyses of polymers Polymer Solvent a Yield (%) M n (kda) M w (kda) PDI PEB-P PEBE-PBP Chlorobenzene Chloroform Chlorobenzene Chloroform PPBP Chloroform a Solvents used for different extraction parts. 11

12 S3. Film formation S3.1 Formation of PEBE polymer films The polymer films of PEBE was electrochemically polymerized from the filtered DCM solution dissolving 5 mm EBE and 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF 6 ). The electrochemical polymerization was operated in a three-electrode cell with on Pt or ITO-coated glass slides as the working electrode, Pt wire as the counter electrode and non-aqueous Ag/Ag + electrode as the reference electrode. After 4 cyclic voltammetric cycles from -0.4 V to 1.4 V with the scan rate of 20 mv s -1, 5 cyclic voltammetric cycles from -0.1 V to 0.9 V with the scan rate of 100 mv s -1, the polymer films was formed on the Pt and ITO-coated glass slides, respectively. For specific capacitance test, the PEBE polymer films were electrochemically polymerized on Au electrode under 4 cyclic voltammetric cycles from -0.4V to 1.4 V with the scan rate of 20 mv s -1, and the Ag wire served as the quasi-reference electrode. Both electrochemical polymerization and electrochemical experiments were performed using a Gamry Interface 1000 electrochemical workstation. 12

13 Figure S12. Electrochemical polymerization of EBE on (a) Pt electrode at scan rate of 50 mv s -1 and (b) Au electrode at scan rate of 20 mv s -1. S3.2 Formation of PEBE-PBP, PEB-P and PPBP polymer film PEBE-PBP, PEB-P and PPBP were fully dissolved in the chloroform and chlorobenzene solution with the ratio of 4:1 to get 1 mg ml -1 solution. The solution was filtered via a needle of 0.45 mm diameter, to remove any undissolved particle and avoid blockage in spray nozzle. During spray coating, a steady airflow was kept pumped into the spray gun to obtain a uniform film on Pt or ITO-coated glass slides. The spray-coated films were dried under vacuum for 30 min at 60 C to remove any remaining solvent absorbed within the polymer. S4. Spectroelectrochemistry of PEBE, PPBP, PEBE-PBP and PEB-P 13

14 Figure S13. Spectroelectrochemistry of (a) PEBE, (b) PPBP, (c) PEBE-PBP, (d) PEB-P polymer films on ITO-coated glass slides in a 0.1 M TBAPF 6 /PC electrolyte solvent at different potentials. S5. Specific capacitance calculation S5.1 Mass-absorbance estimation method The mass of PEBE-PBP and PEB-P on Pt electrode is too little to be weighed accurately and thus the mass was calculated approximately based on the Beer-Lambert Law. The optical characteristics of materials are related to physical or chemical properties. 7 Beer Lambert law states a linear relationship between absorbance (A) and concentration of light absorbing species (c) for certain material tested under fixed optical pathlength (l) (eq S1). With certain linear relationship in hand, concentration could be translated from the absorbance according to eq S1: A = klc (S1) where k is absorption coefficient. Figure S14. Absorbance-concentration linear fit of the (a) PEBE-PBP, (b) PEB-P. 14

15 To establish the linear formula between absorbance and concentration of obtained polymers, absorbance of PEBE-PBP and PEB-P solution with concentrations ranging from 6ug/ ml to 40ug/mL in chlorobenzene was examined and linear fitted with corresponding concentration (Figure S14). Excellent linearity was observed in both novel polymers, demonstrating the workability of Beer-Lambert law. With respect to the linear relationship listed in Figure S14, solution concentration (c ' ) could be converted from the obtained absorbance. If polymer films on Pt electrode were dissolved into chlorobenzene with certain volume (V), the mass (m) can be further calculated in the line with eq S2. m = c'v (S2) Based on the theoretical basis above, mass-absorbance estimation method could be utilized to access the mass of polymer on electrode. After electrochemical property test, the polymer on electrode was dissolved in 3mL chlorobenzene and absorbance of the solution was examined. With concentration translated from obtained absorbance and known volume, mass of polymer films could be successfully estimated. S5.2 Quartz crystal microbalance (QCM) method The piezoelectric oscillation of a quartz resonator has been used as an ultrasensitive mass sensor, utilizing the Sauerbrey relationship between the resonant frequency and the mass per unit area deposited on the crystal. 8 Hence a Gamry 10M electrochemical quartz crystal microbalance (EQCM) was used during electrochemical deposition to access the mass of insoluble polymer PEBE. The electrochemical polymerization was operated in a three-electrode cell consisted of a Ag wire as the 15

16 reference electrode, a Pt wire as the counter electrode, and an Au-coated quartz sensors ( , Gamry) with diameter of 12 mm and fundamental resonant frequency of 5 MHz as work electrode. At the same time of deposition, resonance frequency of films on the sensor were characterized through EQCM. With respect to Sauerbrey expression (eq S3): f = C f m s (S3) where Cf is the correction factor determined by fundamental resonant frequency of used quartz sensor, and s is the surface area of Au electrode. The mass of electroactive polymer deposited on quartz sensor ( m) could be related to the change in resonance frequency ( f). S5.3 Specific capacitance calculation Specific capacitance (C m, F g -1 ) was measured by galvanostatic charge-discharge in a three-electrode configuration and calculated with eq S4: C m = ita mv (S4) where i is the current density, A is the area of polymer electrode, t and V are the discharge time and work voltage change during discharge process, respectively. And m is the mass of electroactive polymer on single electrode. S5.4 The number of electrons stored per polymer unit According to galvanostatic charge-discharge tests, the number of stored electrons (n e ) could be obtained through dividing charges stored in p-doping or n-doping process (Q) by the charges for one electron (e): n e = Q e = ita e (S5) 16

17 where e is C. Meanwhile, the number of polymer unit (n Unit ) could be obtained by following eq S6: n Unit = m M a N A = man A M (S6) where M is the molecular weight of repeating unit, a is the number of donor or acceptor unit per repeating unit, and Avogadro constant (N A ) is mol -1. Therefore, the number of electrons stored per donor or acceptor unit (N) could be calculated according to eq S5: N = n e n Unit = itam eman A (S7) Table S2. The number of electrons stored per polymer unit Polymer M (g mol -1 ) m (μg) i (ma cm -2 ) A (cm 2 ) Doping process t (s) a N PEBE p n PEBE-PBP p n PEB-P p n Based on Table S2, the ratios of electron numbers per unit among polymers (PEBE : PEBE-PBP : PEB-P) have been obtained: 1 : 1 : 0.87 for p-doping process and 1 : 0.91 : 0.90 for n-doping process. Comparing to PEBE, the decreased electron numbers of both recombined polymers could result from 17

18 different film formation methods (spray coating and electrochemical deposition) or indeterminate contribution from double-layer behavior. S6. Capacitance and stability of PEBE-PBP and PEB-P with literature Table S3. Capacitance and stability of representative ambipolar polymer electrode materials reported in the literature Polymer Structure Electrode Capacitance Stability formation (condition and voltage range) (retention, cycles, current) Electrochemical Symmetric devices: Symmetric devices: deposition 72 F g -1, 0.5 A g -1 (0.3 V) 75% retention after 100 cycles, Ref F g -1, 50 mv s -1 (2.5 V) 30% retention after 1000 cycles Electrochemical Symmetric devices: --- deposition 40 F g -1, 0.5 A g -1 (0.675 V) Ref F g -1, 100 mv s -1 (2.5 V) Electrochemical Single electrode: Device: deposition C mp : 1.7 mf cm -2 (0.7 V) 50% retention after 100 cycles, Ref. 10 C mn: --- nearly depleted after 200 cycles Device: 14 F g -1, 50 mv s -1 (0.5 V) Electrochemical C mp : 159 F g -1, 30 A g -1 (0.7 V) P: 41% retention after 400 deposition C mn : 147 F g -1, 20 A g -1 (0.7 V) cycles, 150 mv s -1 Ref. 11 N: 89% retention after 1000 cycles, 150 mv s -1 18

19 Ref. 12 Electrochemical deposition Electrochemical deposition C mp : 473 F g -1, 50 mv s -1 (0.34V ) C mn : 336 F g -1, 50 mv s -1 (0.44V ) C all : 135 F g -1, 50 mv s -1 (2.3V ) C mp : 571 F g -1, 50 mv s -1 (0.33V ) C mn : 286 F g -1, 50 mv s -1 (0.32V ) C all : 133 F g -1, 50 mv s -1 (2.1V ) Device: 56% of initial capacitance after 2000 cycles, 0.05 ma cm -2 Device: 83% of initial capacitance after 2000 cycles, 0.05 ma cm -2 Ref. 12 Our work Spray coating C mp : F g -1, 0.05mA cm -2 (1.3V ) C mn : F g -1, 0.05mA cm -2 (1.3V ) C all : F g -1, 0.05mA cm -2 (2.6V ) P: 60% retention after 2000 cycles, 1.25mA cm -2 N: 63% retention after 250 cycles, 50 mv s -1 Our work Spray coating C mp : F g -1, 0.05mA cm -2 (1.3V) C mn : F g -1, 0.05mA cm -2 (1.3V) C all : F g -1, 0.05mA cm -2 (2.6V ) P: 50% retention after 2000 cycles, 1.25mA cm -2 N: 25% retention after 250 cycles, 50 mv s -1 S7. Stability test of PEBE-PBP, PEB-P and PEBE in p-doped state 19

20 Figure S15. Stability in p-doped state of (a) PEBE-PBP, (b) PEB-P, (c) PEBE polymer films on Pt electrode recorded in 0.1 M TBAPF 6 /PC. S8. EIS test of PEBE-PBP and PEB-P at oxidized, neutral and reduced states Figure S16. Nyquist plots of (a) PEBE-PBP and (b) PEB-P polymer films at oxidized (0.8 V), neutral (- 0.7 V) and reduced (- 1.8 V) states on Pt disk electrode measured in 0.1 M TBAPF 6 /ACN. S9. SEM image of PEBE-PBP and PEB-P polymer films on ITO-coated glass slides 20

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