Substituent Effect on Electrochemical and Electrochromic Properties of Aromatic Polyimides with 4-(Carbazol-9-yl)triphenylamine Units

Substituent Effect on Electrochemical and Substituent Effect on Electrochemical and ElectrochromicElectrochromic Properties of Properties of Aromatic Aromatic PolyimidesPolyimides with 4with 4--(Carbazol(Carbazol--99--yl)triphenylamine Unitsyl)triphenylamine Units

Hui-Min Wang (王惠民), Sheng-Huei Hsiao* (蕭勝輝)Department of Chemical Engineering and Biotechnology, National Taipei University of TechnologyE-mail: shhsiao@ntut.edu.tw

ElectrochromicElectrochromic TechnologyTechnology

Three series of aromatic polyimides with 4-(carbazol-9-yl)triphenylamine units were prepared from the polycondensation reactions of 4,4’-diamino-4’’-(3,6-dimethoxycarbazol-9-yl)triphenylamine (1), 4,4’-diamino-4’’-(3,6-di-tert-butylcarbazol-9-yl)triphenylamine (t-Bu-1), and 4,4’-diamino-4’’-(3,6-dimethoxycarbazol-9-yl)triphenylamine (MeO-1), respectively, with various commercially available tetracarboxylic dianhydrides. In addition to high glass-transition temperatures, high thermal stability, and good solution processability, the resulting polyimides exhibited an ambipolar electrochromic behavior. The polyimides from MeO-3 revealed, lower oxidation potentials, more stable electrochemical oxidation process, and higher electrochromic reversibility than the corresponding 3 and t-Bu-3 series polyimides because the active sites of their carbazole units are blocked with electron-donating methoxy groups.

ElectrochromismElectrochromism

TABLE 3 Redox Potentials and Energy Levels of Polyimides

Our strategy of this work is to design and synthesize CzTPA-based electrochromic polyimides with methoxy or tert-butyl groups on C-3 and C-6 sites of the carbazole, thus could greatly prevent the coupling reactions by affording stable cationic radicals.

1. Monk, P. M. S.; Mortimer, R. J.; Rosseinsky, D. R. Electrochromism and Electrochromic Devices, Cambridge University Press, Cambridge, UK, 2007.

2. (a) Ambrose, J. F.; Nelson, R. F. J Electrochem Soc 1968, 115, 1159-1164; (b) Ambrose, J. F.; Carpenter, L. L.; Nelson, R. F. J Electrochem Soc 1975, 122, 876-894.

3. Liou, G.-S.; Hsiao S.-H.; Chen H.-W. J. Mater. Chem. 2006, 16, 1831-1842

4. Wang, H.-M.; Hsiao, S.-H.; Liou, G.-S.; Sun, C.-H. J. Polym. Sci. Part A: Polym. Chem. 2010, 48, 4775-4789

5. Mazur, S.; Lugg, P. S.; Yarnitzky, C. J. Electrochem. Soc., 1987, 134, 346–353;

Cyclic Cyclic VoltammogramVoltammogram

＋＋＋h＋h＋＋＋＋＋＋0.521.503d

－＋h＋h＋h＋h＋h－1.693c

－＋h－－－＋－－1.743b

－－＋－＋－＋－＋－－1.933a

＋＋＋＋＋h＋＋＋＋＋＋0.392.64t-Bu 3a

＋＋＋＋＋h＋＋＋＋＋＋0.511.63t-Bu 3a

－＋h－－－＋h－1.72t-Bu 3a

＋－＋－＋－＋－＋－＋－－1.36t-Bu 3a

＋＋

＋－

＋－

＋－

DMF

＋＋

＋－

＋－

＋－

DMAc

＋＋

＋＋

＋h

＋－

NMP

Solubility in various solventsb

1.80

1.46

ηinha(dL/g)Polymer

Code

＋＋＋＋＋h0.65MeO-3a

＋－＋h＋－－0.91MeO-3a

＋－＋h＋－－MeO-3a

＋－＋－＋－－1.52MeO-3a

THFm-CresolDMSOPIPAA

a Inherent viscosity measured at a concentration of 0.5 dL/g in DMAc at 30 oC. PAA = Poly(amic acid), PI = Polyimide. b Qualitative solubility was tested with 10 mg of a sample in 1 mL of a stirred solvent. ＋＋: soluble at room temperature; ＋h: soluble on heating; ＋－: partial soluble on heating; －: insoluble even on heating. c NMP: N-methyl-2-pyrrolidone; DMAc: N,N-dimethylacetamide; DMF: N,N-dimethylformamide; DMSO: dimethyl sulfoxide; THF: tetrahydrofuran.

P. M. S. Monk, R. J. Mortimer and D. R. Rosseinsky, Electrochromism and Electrochromic Devices, Cambridge University Press, Cambridge, UK, 2007.

A reversible optical change observed in a material because of an applied external voltage is defined as electrochromism

WO3 + x (Li+ + e

-) LixWO3

colorless blue

Smart WindowsCar Rear-View Mirrors Displays

3.185.442.263.23－-1.10-0.901.40f1.080.93383299, 3303d

3.035.422.393.22－-1.25-1.041.36f1.060.90385299, 3283c

3.195.432.243.20-1.28-1.09-0.811.38f1.070.91387299, 3313b

3.635.411.782.96-1.26-0.65-0.571.40f1.050.89419299, 3203a

3.175.412.243.17－-1.11-0.921.281.050.88391299, 331t-Bu 3a

3.035.392.363.16－-1.25-1.051.311.030.88393299, 331t-Bu 3a

3.185.382.203.16-1.31-1.10-0.821.301.020.90393299, 336t-Bu 3a

3.615.371.762.95-1.29-0.67-0.551.291.010.92420299, 315t-Bu 3a

391

396

397

418

λonset

303, 333

313, 347

312, 345

313, 360

λmax

Thin films (nm)

1.19

1.19

1.19

1.20

E1/2Ox2

0.90

0.90

0.91

0.92

E1/2Ox1

0.78

0.75

0.75

0.74

Eonset

Oxidation Potentiala (V)

3.125.311.863.17－-1.16-0.88MeO-3a

Energy leveld (eV)Bandgapc (eV)Reduction Potentialb (V)

-1.31

-1.14

-0.80

E1/2Red1

-0.97

-0.87

-0.51

Eonset

3.10

3.08

2.98

Egop

－

-1.32

-1.37

E1/2Red2

2.975.262.29MeO-3a

3.145.272.13MeO-3a

3.485.281.80MeO-3a

LUMOHOMOEgec

Polymer

Code

TABLE 1 Inherent Viscosity and Solubility Behavior of Polyimides

a Measured as thin films. b vs. Ag/AgCl in CH3CN. E1/2 = Average potential of the redox couple peaks. c vs. Ag/AgCl in DMF. d Bandgaps calculated from absorption edge of the polymer films: Eg

opt = 1240/λonset. Egec, electrochemical band gap is derived from the difference between HOMO and LUMO values. e The HOMO and LUMO

energy levels were calculated from E1/2Ox1 and E1/2

Red1 values of CV curves and were referenced to ferrocene (4.8 eV; E1/2= 0.44 V in CH3CN; E1/2 = 0.52 V in DMF). f

The second oxidation redox couple is irreversible.

SpectroelectrochemistrySpectroelectrochemistry of PIs for pof PIs for p--dopingdopingRepeated CV diagrams Repeated CV diagrams

Literature Discussion and Research MotivationLiterature Discussion and Research Motivation

ABSTRACT

INTRODUCTION

EXPERIMENTAL

REFERENCES AND NOTES

Monomer SynthesisMonomer Synthesis Polymer SynthesisPolymer Synthesis

RESULTS AND DISCUSSION

725766423103d

736276483033c

746346523253b

72627640－e3a

63565564333t-Bu 3a

66560581320t-Bu 3a

70583583336t-Bu 3a

66552568318t-Bu 3a

Td at 10 wt% ( oC )bPolymer Code

59492529324MeO-3a

62514571306MeO-3a

71525577337MeO-3a

68498552320MeO-3a

Char yield (wt %)cIn airIn N2

Tg ( oC )a

TABLE 2 Thermal Properties of Polyimides

a The polymer film samples were heated at 300 °C for 30 min before all the thermal analyses. b

Midpoint temperature of the baseline shift on the second DSC heating trace (rate = 20 oC/min) of the sample after quenching from 400 to 50 oC (cooling rate = -200 oC/min) in nitrogen. c Decomposition temperature at which a 10% weight loss was recorded by TGA at a heating rate of 20 oC/min and a gas flow rate of 20 cm3/min. d Residual weight percentage at 800 oC in nitrogen. e No discernible transition was detectable by DSC..

(b)(b)First and second redox couples

(a)(a)

Liou, G.-S.; Hsiao, S.-H.; Chen, H.-W. J. Mater. Chem. 2006, 16, 1831-1842

N

N O

O

O

O

N N

CF3F3C

n n

N

N O

O

O

O

N N

CF3F3C

First redox couple

TPPACzTPA

J. Mater. Chem. 2007, 17, 1007-1015J. Mater. Chem. 2007, 17, 1007-1015

Macromolecules 2008, 41, 1667-1674Macromolecules 2008, 41, 1667-1674

JPSA 2006, 44, 4579-4592JPSA 2006, 44, 4579-4592R = t-butyl

R = MeO

R = t-butyl

R = MeO

JPSA 2009, 47, 2330-2343JPSA 2009, 47, 2330-2343

R = t-butyl

R = MeO J. Mater. Chem. 2008, 18, 5638-5646 J. Mater. Chem. 2008, 18, 5638-5646

JPSA 2011, 49, 337-351JPSA 2011, 49, 337-351

R = t-butyl

R = MeO

R = t-butyl

R = MeO

N

H

C

O

N

H

C

O

?

JPSA 2008, 46, 7937-7949JPSA 2008, 46, 7937-7949

Polymer 2009, 50, 1692-1699Polymer 2009, 50, 1692-1699

Not yet published

Scheme 1 Synthetic routes to diamine monomers 1, t-Bu-1 and MeO-1.

(1) Liou, G.-S.; Hsiao, S.-H.; Chen, H.-W. J. Mater. Chem. 2006, 16, 1831-1842.(2) Wang, H.-M.; Hsiao, S.-H.; Liou, G.-S.; Sun, C.-H. J. Polym. Sci. Part A: Polym. Chem. 2010, 48, 4775-4789.

Ref. (2) Ref. (1)

Scheme 3.2 Synthesis of polyimides by two-step imidization.

Scheme 3.3 Synthesis of model compounds.

Figure 1. IR and 1H NMR spectra of polyimides (a) 3d, (b) t-Bu-3d, and (c)MeO-3d in CDCl3. (* the solvent peak).

IR and NMR spectra of IR and NMR spectra of PolyimidesPolyimides

Cyclic Cyclic VoltammogramsVoltammograms of of PolyimidesPolyimides for nfor n--dopingdoping

TABLE 4 Electrochromic Properties of Polyimides

79

768

55

400

88

771

62

404

88

817

51

414λmax (nm)

Polymer

Δ%T

Colors

Ar

859643495723654564λmax (nm)

203219803570Δ%T

67

-6

4

-1.05

96

-2

3

0.0

96

1

3

0.0

53

25

-17

-1.60

53

-2

6

-1.45

60

3

20

-1.25E (V)

L*

a*

b*

N

NN

O

O

O

O

Ar

N

n N

NN

O

O

O

O

Ar

N

nN

NN

O

O

O

O

Ar

N

n

H3CO OCH3

Colors

49

-1

-4

1.5

55

2

0

1.1

95

-1

2

0.0

49

-6

-15

1.4

57

3

-3

1.15

96

-2

1

0.0

53

-2

6

1.05

96

1

3

0.0

37

-5

-22

L*

a*

b*

E (V) 1.3

3d

t-Bu-3d MeO-3d

SpectroelectrochemistrySpectroelectrochemistry of PIs for nof PIs for n--dopingdoping

MeO-3a MeO-3b