Multicolor electrochromic poly(amide-imide)s with N,N

PAPER www.rsc.org/polymers | Polymer Chemistry

Multicolor electrochromic poly(amide-imide)s with N,N-diphenyl-N0,N0-di-4-tert-butylphenyl-1,4-phenylenediamine moieties†

Hui-Min Wang and Sheng-Huei Hsiao*

Received 25th February 2010, Accepted 6th April 2010

DOI: 10.1039/c0py00065e

A new imide ring-preformed dicarboxylic acid monomer bearing the N,N,N0,N0-tetraphenyl-1,4-

phenylenediamine (TPPA) unit, i.e., N,N-bis(4-tert-butylphenyl)-N0,N0-bis(4-carboxyphthalimido)-1,4-

phenylenediamine (2), was synthesized from the condensation of N,N-bis(4-aminophenyl)-N0,N0-bis(4-

tert-butylphenyl)-1,4-phenylenediamine (1) and two equivalent amount of trimellitic anhydride

(TMA). A new series of aromatic poly(amide-imide)s (PAIs) 4a–4g containing the electroactive TPPA

moiety were prepared from the diimide-diacid 2 with various aromatic diamines by the

phosphorylation polyamidation reaction. All the polymers were readily soluble in many organic

solvents and could be solution-cast into tough and flexible polymer films. They displayed moderate to

high glass-transition temperatures (280–320 �C) and good thermal stability. For the PAIs derived from

common aromatic diamines, cyclic voltammograms of their cast films on the indium–tin oxide (ITO)-

coated glass substrate exhibited two reversible oxidation redox couples around 0.68 and 1.10 V vs. Ag/

AgCl in acetonitrile solution, and they revealed high redox and electrochromic stability with a color

change from colorless neutral form to yellow and blue oxidized forms at applied potentials scanning

from 0.0 to 1.3 V. Cyclic voltammograms of PAIs 4f and 4g obtained from diimide-diacid 2 and

triphenylamine-based diamines exhibited three and four reversible oxidation redox couples,

respectively. Because there are more than two redox states are electrochemically accessible from PAIs 4f

and 4g, they could form tristable and even tetrastable color species and thus could display several colors

upon oxidation at varying applied voltages. The electrochromic performance of a representative PAI 4c

was investigated. This anodically coloring polymer film showed good electrochromic properties with

high coloration efficiency (CE ¼ 268 cm2 C�1 for the yellow coloration) and high optical contrast ratio

of transmittance change (DT%) up to 33% at 411 nm and 32% at 922 nm for the yellow coloring, and

72% at 698 nm for the blue coloring. After over 100 cyclic switches, the polymer films still retained

excellent redox and electrochromic activity.

Introduction

Electrochromic materials exhibit a change in optical absorption

or transmittance upon redox switching. There are many chemical

systems that are intrinsically electrochromic, such as transition

metal oxides, inorganic coordination complexes, organic mole-

cules, and conjugated polymers.1 Traditionally, interest in elec-

trochromic materials has been directed towards optical changes

in the visible region, leading to many technological applications

such as variable reflectance mirrors, tunable windows, and elec-

trochromic displays.2 Of the available electrochromic materials,

conjugated conducting polymers such as poly(3,4-alkylenedioxy-

thiophene) and poly(3,4-alkylenedioxypyrrole) based polymers

and other similar systems have become widely researched elec-

trochromic materials because of their fast switching speeds,

improved processability, and color tunability through structural

modification.3–5 In recent years, we have carried out extensive

studies on the design and synthesis of triarylamine-based high-

Department of Chemical Engineering and Biotechnology, National TaipeiUniversity of Technology, 1 Chunghsiao East Road, 3rd Section, 10608Taipei, Taiwan, ROC. E-mail: [email protected]

† Electronic supplementary information (ESI) available: o. See DOI:10.1039/c0py00065e

This journal is ª The Royal Society of Chemistry 2010

performance polymers such as aromatic polyamides and poly-

imides for electrochromic applications.6 The electrochromic

function of these polymers came from the triarylamine core

which can be easily oxidized and the resulting radical cation is

stable enough and can undergo long-standing redox cycles.

Aromatic poly(amide-imide)s (PAIs) possess balanced char-

acteristics between polyamides and polyimides such as high

thermal stability and good mechanical properties together with

ease of processability.7 Since we successfully applied the Yama-

zaki-Higashi phosphorylation reaction8 to the direct synthesis of

high-molecular-weight PAIs from the TMA-derived imide ring-

bearing dicarboxylic acids and aromatic diamines using triphenyl

phosphite (TPP) and pyridine as condensing agents,9 this efficient

synthetic route has proved to exhibit significant advantages in

preparing operations as compared with conventional acid chlo-

ride or isocyanate methods.10 Thus, many novel PAIs have been

readily prepared by this convenient technique in our and other

laboratories.11 Furthermore, this synthetic procedure can offer

us the option of the incorporation of specific functionalities

between amide or imide groups in the PAI backbone. The

incorporation of such functional groups may provide a method

of controlling certain physical properties or special functions of

the resulting PAIs.

Polym. Chem., 2010, 1, 1013–1023 | 1013

Fig. 1 (a) 1H-NMR and (b) 13C-NMR spectra of diimide-diacid 2 in

DMSO-d6.

The redox properties, ion-transfer process, and electrochromic

behavior of N,N,N0,N0-tetraphenyl-1,4-phenylenediamine

(TPPA) derivatives are important for technological application.12

The radical cations of TPPA derivatives such as N,N,N0,N0-tetra-

4-methoxyphenyl-1,4-phenylenediamine showed rather strong

intervalence charge-transfer (IV-CT) bands in near infrared

(NIR) region as measured by UV/Vis/NIR spectroelec-

trochemistry.13 Recently, it has been demonstrated that aromatic

polyamides containing TPPA moieties reveal interesting elec-

trochromic characteristics, such as polyelectrochromism, high

coloration efficiency, fast response time, high optical contrast,

and excellent redox stability.14 Herein, we report the synthesis

and characterization of a new family of TPPA-containing

aromatic PAIs based on the diimide-diacid 2 which was prepared

from the condensation of N,N-bis(4-aminophenyl)-N0N0bis(4-

tert-butylphenyl)-1,4-phenylenediamine (1) and TMA. With such

a configuration, the electrochemically active sites of the pendent

phenyl groups of the TPPA unit are blocked, giving the polymers

extra electrochemical stability. As a result, these PAIs were found

to possess an enhanced redox and electrochromic stability. In

addition, the PAIs obtained from the polymerization reactions of

diimide-diacid 2 with triphenylamine-based diamine and TPPA-

containing diamine exhibited a multi-colored electrochromic

behavior due to the presence of three or four redox-active amino

centers in the repeat unit.

Experimental part

Materials

The TPPA-containing diamine monomer 1 was synthesized by

a four-step reaction sequence starting from bis(tert-butylphe-

nyl)amine and p-fluoronitrobenzene.15 The commercially avail-

able diamine monomers including p-phenylenediamine (3a),

m-phenylenediamine (3b), 4,40-diaminodophenyl ether (3c), and

9,9-bis(4-aminophenyl)fluorene (3e) were used as received from

Tokyo Chemical Industry. According to a procedure reported

previously,16 2-triflouromethyl-4,40-diaminodiphenyl ether (3d)

(mp: 112–113 �C) was synthesized by the chloro-displacement

reaction of 2-chloro-5-nitrobenzotrifluoride with p-nitrophenol

in the presence of potassium carbonate, followed by the hydra-

zine palladium-catalyzed reduction of the intermediate dinitro

compound. 4,40-Diamino-40 0-tert-butyltriphenylamine (3f) (mp:

113–115 �C)6c was synthesized by the caesium fluoride-mediated

condensation of 4-tert-butylaniline with p-fluoronitrobenzene,

followed by a palladium-catalyzed hydrazine reduction. N-

Methyl-2-pyrrolidone (NMP) was dried over calcium hydride for

24 h, distilled under reduced pressure, and stored over 4 �A

molecular sieves in a sealed bottle. Commercially obtained

calcium chloride (CaCl2) was dried under vacuum at 180 �C for 3

h prior to use. Tetrabutylammonium perchlorate, Bu4NClO4,

was recrystallized from ethyl acetate under nitrogen atmosphere

and then dried in vacuo prior to use. All other reagents and

solvents were used as received from commercial sources.

Monomer synthesis

N,N-Bis(4-tert-butylphenyl)-N0,N0-bis(4-carboxyphthalimido)-

1,4-phenylenediamine (2). A flask was charged with 5.4 g (10

mmol) of diamine 1, 4.0 g (20 mmol) of trimellitic anhydride, and

1014 | Polym. Chem., 2010, 1, 1013–1023

50 mL of glacial acetic acid. The heterogeneous mixture was

refluxed for 12 h. After cooling, the mixture was poured into 300

mL of methanol, and the precipitate was collected by filtration

and washed thoroughly with methanol. The crude product

obtained was purified by recrystallization from N,N-dime-

thylformamide (DMF) and then dried in vacuum to afford 7.2 g

(80% yield) of diimide-dicarboxylic acid monomer 2 as pale

brown solid, mp ¼ 321–323 �C. IR (KBr): 2700–3400 (O–H str.),

2964 (t-butyl C–H str.), 1778, 1724 cm�1 (imide C]O str.). 1H

NMR (500 MHz, DMSO-d6, d, ppm) (for the peak assignments,

see Fig. 1a): 1.27 (s, 18H, t-butyl), 6.98 (d, J ¼ 8.9 Hz 2H, Hd),

6.99 (d, J¼ 8.6 Hz, 4H, Hb), 7.11 (d, J¼ 8.8 Hz, 2H, Hc), 7.18 (d,

J¼ 8.8 Hz, 4H, He), 7.33 (d, J¼ 8.6 Hz, 4H, Ha), 7.39 (d, J¼ 8.8

Hz, 4H, Hf), 8.07 (d, J ¼ 7.8 Hz, 2H, Hh), 8.30 (s, 2H, Hg), 8.41

(d, J ¼ 7.8 Hz, 2H, Hi).13C NMR (125 Hz, DMSO-d6, d, ppm)

(for the peak assignments, see Fig. 1b): 31.2 (C1), 34.0 (C2), 122.5

(C12), 123.3 (C17), 123.5 (C5), 123.7 (C20), 124.1 (C9), 125.7 (C16),

126.2 (C4), 127.1 (C8), 128.3 (C13), 132.0 (C21), 134.9 (C18), 135.4

(C19), 136.4 (C11), 140.4 (C10), 144.3 (C7), 144.6 (C6), 145.2 (C3),

146.8 (C14), 165.8 (–COOH), 166.37, 166.38 (imide carbonyl

carbons). Anal. Calcd for C56H46N4O8 (903.00): C, 74.49%; H,

5.13%; N, 6.20%. Found: C, 74.15%; H, 5.06%; N, 6.15%.

Polymer synthesis

The synthesis of PAI 4a is used as an example to illustrate the

general synthetic route. A mixture of 0.6321 g (0.7 mmol) of the

diimide-dicarboxylic acid 2, 0.0757 g (0.7 mmol) of p-phenyl-

enediamine (3a), 0.15 g of calcium chloride, 1.0 mL of triphenyl

phosphite, 0.3 mL of pyridine, and 1.7 mL of NMP was heated

with stirring at 120 �C for 3 h. The resulting viscous solution was


poured slowly with stirring into 150 mL of methanol, giving rise

to a tough, fibrous precipitate. The precipitated product was

collected by filtration, washed repeatedly with methanol and hot

water, and dried to give a quantitative yield of PAI 4a. The

inherent viscosity of the polymer was 0.61 dL/g, measured in

DMAc (containing 5 wt% LiCl) at a concentration of 0.5 g/dL at

30 �C. The IR spectrum of 4a (film) exhibited characteristic

amide absorption bands at 3200–3400 cm�1 (amide N–H str.) and

1675 cm�1 (amide carbonyl str.), together with the imide

absorption bands at 1778 cm�1 (asymmetrical C ] O str.), 1724

cm�1 (symmetrical C ] O str.), and 725 cm�1 (imide ring

deformation).

Preparation of the PAI films

A solution of polymer was made by dissolving about 0.6 g of the

PAI sample in 10 mL of DMAc. The homogeneous solution was

poured into a 9 cm glass Petri dish, which was placed in a 90 �C

oven overnight to remove most of the solvent. The cast film was

then released from the glass substrate and was further dried in

vacuo at 160 �C for 8 h. The obtained films were about 50–60 mm

in thickness and were used for X-ray diffraction measurements,

solubility tests and thermal analyses.

Measurements

Infrared (IR) spectra were recorded on a Horiba FT-720 FT-IR

spectrometer. Elemental analyses were run in a Heraeus VarioEL

III CHNS elemental analyzer. 1H- and 13C-NMR spectra were

measured on a Bruker AVANCE 500 FT-NMR system with

tetramethylsilane as an internal standard. The inherent viscosi-

ties were determined with a Cannon-Fenske viscometer at 30 �C.

Wide-angle X-ray diffraction (WAXD) measurements were

performed at room temperature (ca. 25 �C) on a Shimadzu XRD-

6000 X-ray diffractometer with a graphite monochromator

(operating at 40 kV and 30 mA), using nickel-filtered Cu-Ka

radiation (l ¼ 1.5418 �A). The scanning rate was 2� min�1 over

a range of 2q ¼ 10–40�. Thermogravimetric analysis (TGA) was

performed with a Perkin-Elmer Pyris 1 TGA. Experiments were

carried out on approximately 4–6 mg of samples heated in

flowing nitrogen or air (flow rate ¼ 40 cm3 min�1) at a heating

rate of 20 �C min�1. DSC analyses were performed on a Perkin-

Elmer Pyris 1 DSC at a scan rate of 20 �C min�1 in flowing

nitrogen. Thermomechanical analysis (TMA) was determined

with a Perkin-Elmer TMA 7 instrument. The TMA experiments

were carried out from 50 to 400 �C at a scan rate of 10 �C min�1

Scheme 1 Synthesis of diim


with a penetration probe 1.0 mm in diameter under an applied

constant load of 10 mN. Softening temperatures (Ts) were taken

as the onset temperatures of probe displacement on the TMA

traces. Ultraviolet-visible (UV-Vis) spectra of the polymer films

were recorded on an Agilent 8453 UV-Visible spectrometer.

Electrochemistry was performed with a CHI 611C electro-

chemical analyzer. Voltammograms are presented with the

positive potential pointing to the left and with increasing anodic

currents pointing downwards. Cyclic voltammetry was con-

ducted with the use of a three-electrode cell in which ITO

(polymer films area about 0.8 cm � 1.25 cm) was used as

a working electrode. A platinum wire was used as an auxiliary

electrode. All cell potentials were taken with the use of a home-

made Ag/AgCl, KCl (sat.) reference electrode. Ferrocene was

used as an external reference for calibration (+0.48 V vs. Ag/

AgCl). Spectroelectrochemistry analyses were carried out with an

electrolytic cell, which was composed of a 1 cm cuvette, ITO as

a working electrode, a platinum wire as an auxiliary electrode,

and a Ag/AgCl reference electrode. Absorption spectra in the

spectroelectrochemical experiments were measured with an

Agilent 8453 UV-Visible spectrophotometer. Coloration effi-

ciency is derived from the equation: h ¼ DOD/Q,17 DOD is

optical density change at specific absorption wavelength and Q is

ejected charge determined from the in situ experiments. Photo-

luminescence (PL) spectra were measured with a Varian Cary

Eclipse fluorescence spectrophotometer. Fluorescence quantum

yields (FF) of the samples in NMP were measured by using

quinine sulfate in 1 N H2SO4 as a reference standard

(FF ¼ 54.6%).18 All corrected fluorescence excitation spectra

were found to be equivalent to their respective absorption

spectra.

Results and discussion

Monomer synthesis

The TPPA-containing diimide-dicarboxylic acid monomer,

N,N-bis(4-tert-butylphenyl)-N0,N0-bis(4-carboxyphthalimido)-

1,4-phenylenediamine (2), was obtained by reacting diamine 1

with 2 mol equiv of trimellitic anhydride (TMA) in refluxing

glacial acetic acid (Scheme 1). IR, 1H-NMR, and 13C-NMR

spectroscopic techniques were used to identify the structure of

the targeted diimide-dicarboxylic acid 2. The IR spectrum of 2

(Fig. S1, ESI†) showed absorption bands around 2700–3400

(–OH, carboxylic acid), 1778 (imide C]O asymmetrical

stretching), and 1724 cm�1 (imide C]O symmetrical stretching

ide-dicarboxylic acid 2.

Polym. Chem., 2010, 1, 1013–1023 | 1015

and acid C]O stretching), confirming the presence of imide

ring and carboxylic acid groups in the structure. The 1H- and13C-NMR spectra of 2 are illustrated in Fig. 1 with the assign-

ments of all peaks. The assignments of all the resonance signals

were assisted by two-dimensional COSY and HMQC NMR

spectra shown in Fig. S2, ESI.† The resonance signals appearing

at downfield regions (8.41–8.07 ppm) in the 1H-NMR spectrum

are ascribed to the trimellitimido protons. The resonance peaks

in the region of 6.9–7.5 ppm are assigned to the phenylene

protons of the TPPA segment. The signals appeared at 1.27

ppm in the 1H-NMR spectrum and 34.0 ppm (a quaternary

carbon) and 31.2 ppm (a methyl carbon) in the 13C-NMR

spectrum are peculiar to the tert-butyl groups. These results

suggest the successful preparation of the imide ring-preformed

dicarboxylic acid monomer 2.

Synthesis and basic characterization of PAIs

A series of seven PAIs 4a–4g containing tert-butyl-blocked

TPPA units were prepared from the diimide-dicarboxylic acid

2 and various aromatic diamines (3a–3g) by the direct poly-

condensation reaction using triphenyl phosphite (TPP) and

pyridine as condensing agents (Scheme 2).8 The polymerization

proceeded homogeneously throughout the reaction and affor-

ded highly viscous polymer solutions. The products precipi-

tated in a tough fiber-like form when pouring slowly the

resultant polymer solutions into stirred methanol. The

obtained PAIs had inherent viscosities in the range of 0.33–

0.78 dL g�1. The molecular weights of all the PAIs are suffi-

ciently high to permit the formation of flexible and tough films

by casting from their DMAc solutions. Structural features of

these PAIs were confirmed by IR and 1H-NMR spectroscopy.

A typical IR spectrum for the representative PAI 4a is also

included in Fig. S1.† The characteristic absorption bands for

imide ring appear around 1778 cm�1, 1724 cm�1 (imide

C ] O), and 725 cm�1 (imide ring deformation), while bands

Scheme 2 Synthesis

1016 | Polym. Chem., 2010, 1, 1013–1023

of amide groups appear around 3300 and 1675 cm�1. A typical1H-NMR spectrum of PAI 4c is shown in ESI Fig. S3.†

Assignments of each proton are also given in the figure, and

the spectrum is in good agreement with the proposed polymer

structure.

As indicated by the wide-angle X-ray diffraction (WAXD)

patterns shown in Fig. S4 (ESI),† all the polymers were essen-

tially amorphous. Qualitative solubility was determined at 1% w/

v concentration, stirring for 24 h at room temperature and

heating up to the solvent boiling point for those samples which

remained insoluble at room temperature. As shown in Table 1,

all the polymers were highly soluble in polar solvents such as

NMP, DMAc and N,N-dimethylformamide (DMF). As

compared to the corresponding 40 series PAIs, the present series

PAIs exhibited an enhanced solubility because of the increased

flexibility or free volume caused by the introduction of the three-

dimensional TPPA moiety and bulky pendent tert-butyl

substituents into the repeat unit. Thus, the excellent solubility

makes these polymers potential candidates for practical appli-

cation by spin-coating or inkjet-printing processes.

Thermal properties

The thermal properties of the PAIs were investigated by TGA,

DSC and TMA, and the results are summarized in Table 2.

Typical TGA curves of a representative PAI 4a in both air and

nitrogen atmospheres are illustrated in the inset of Fig. 2. TGA

measurements reveal that they possess high thermal stability with

decomposition temperature above 400 �C. Their 10% weight-loss

temperatures in nitrogen and air were recorded in the range of

470–535 and 493–553 �C, respectively. The amount of carbon-

ized residue (char yield) of these polymers in nitrogen atmo-

sphere is more than 62% at 800 �C. The high char yields of these

polymers can be ascribed to their high aromatic content. The

glass-transition temperatures (Tgs) of all the polymers were

observed in the range of 280–320 �C by DSC. All the polymers

of PAIs 4a–4g.


Fig. 2 (a) TMA and (b) TGA curves of PAI 4a with a heating rate of 10

Table 1 Inherent viscosity and solubility of PAIs

Polymer code hinha/dL g�1

Solubility in various solventsb

NMP DMAc DMF DMSO m-Cresol THF

4a 0.61 ++ (�)c ++ (—) + (—) + (—) + (—) + (—)4b 0.47 ++ (++) ++ (++) ++ (++) � (+) ++ (+) ++ (—)4c 0.39 ++ (++) ++ (++) ++ (++) ++ (+) ++ (+) � (�)4d 0.70 ++ (++) ++ (++) ++ (++) � (++) ++ (+) � (�)4e 0.34 ++ (++) ++ (++) ++ (++) ++ (++) ++ (+) ++ (—)4f 0.78 ++ (++) ++ (++) ++ (++) � (�) ++ (+) ++ (—)4g 0.33 ++ ++ ++ ++ ++ �

a Measured at a polymer concentration of 0.5 g dL�1 in DMAc–5 wt% LiCl at 30 �C. b The qualitative solubility was tested with 10 mg of a sample in 1mL of stirred solvent. ++, soluble at room temperature; +, soluble on heating;�, partially soluble; —, insoluble even on heating. c Values in parenthesesare data of analogous polyamides 40 having the corresponding diacid residue as in the 4 series.

indicated no clear melting endotherms up to the decomposition

temperatures on the DSC thermograms. This result also supports

the amorphous nature of these PAIs. Comparing the thermal

properties data, one will find that PAI 4e showed the highest Tg

due to the attachment of bulky lateral fluorene groups thus

restricting the segmental mobility. The softening temperatures

(Ts) of the polymer film samples were determined by the TMA

method with a loaded penetration probe. They are obtained from

the onset temperature of the probe displacement on the TMA

trace. A representative TMA thermogram for PAI 4a is illus-

trated in Fig. 2. In all cases, the Ts values obtained by TMA are

lower (by 15–34 �C) than the Tg values measured by the DSC

experiments (Table 2). This may indicate that these PAIs

exhibited a higher degree of plasticity near Tg because of the

increased free volume caused by the bulky TPPA and tert-butyl

groups.

Table 2 Thermal properties of PAIs

Polymercode Tg/�Ca Ts/

�Cb

Td at 5%weight loss/�Cc

Td at 10%weight loss/�Cc

Charyield (wt %)dIn N2 In air In N2 In air

4a 314 290 423 434 470 493 644b 299 272 453 455 512 515 654c 280 260 447 451 495 515 664d 284 250 449 451 523 498 644e 320 289 486 481 535 540 684f 293 278 474 463 533 521 694g 282 255 474 516 532 553 70

a Midpoint temperature of the baseline shift on the second DSC heatingtrace (rate ¼ 20 �C min�1) of the sample after quenching from 400 to50 �C (rate ¼ �200 �C min�1) in nitrogen. b Softening temperaturemeasured by TMA with a constant applied load of 10 mN at a heatingrate of 10 �C min�1. c Decomposition temperature at which a 5% or10% weight loss was recorded by TGA at a heating rate of 20 �C min�1

and a gas flow rate of 20 cm3 min�1. d Residual weight percentage at800 �C in nitrogen.

and 20 �C min�1, respectively.


Optical and electrochemical properties

The optical properties of the PAIs are investigated by UV-vis

absorption and photoluminescence (PL) spectroscopy. The

results are summarized in Table 3. These polymers exhibit strong

UV-vis absorption bands at 306–313 nm in NMP solution, which

can be attributed to the combinations of n-p* and p–p* tran-

sition originating from the conjugated TPPA moieties. In solid

state, these PAIs showed UV-vis absorption characteristics (lmax

around 306–317 nm) similar to those in the solution. These PAIs

exhibited fluorescence emission maxima around 370–385 nm in

NMP solution with extremely low fluorescence quantum yield

ranging from 0.23% for 4d to 0.47% for 4e. The low fluorescence

efficiency can be attributed to intramolecular charge transfer

quenching effect between the TPPA donor and the imide

acceptor.

The electrochemical behavior of the PAIs was investigated by

cyclic voltammetry (CV) conducted for the cast film on an ITO-

coated glass substrate as working electrode in dry acetonitrile

Polym. Chem., 2010, 1, 1013–1023 | 1017

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1018 | Polym. Chem., 2010, 1, 1013–1023 This journal is ª The Royal Society of Chemistry 2010

(CH3CN) containing 0.1 M of Bu4NClO4 as an electrolyte under

nitrogen atmosphere. The derived oxidation potentials are

summarized in Table 3. Fig. 3 shows the CV curves for PAIs 4c

and 40c. There are two reversible oxidation redox couples with

half-wave potentials (E1/2) of 0.69 V and 1.04 V for PAI 4c and

one reversible oxidation redox couple with E1/2 of 1.00 V for PAI

40c in the oxidative scan. The two oxidation waves of 4c are

separated by about 350 mV, emphasizing the strong electronic

coupling between the amino groups in the TPPA moiety through

the p-phenylene linker. Because of the stability of the films and

good adhesion between the polymer and ITO substrate, the 4c

exhibited excellent redox stability. PAI 4c preserved excellent

elecroactivity after 50 cycles between 0.0 and 1.3 V. Upon

oxidation, the polymer film of 4c exhibited a multi-electro-

chromic behavior; a color change from colorless to yellow at 0.8

V and then to blue at 1.2 V. For PAI 4c, the two oxidations

observed correspond to successive one electron removal from the

TPPA functionality of 4c to yield, first, a stable, delocalized

TPPA radical cation and, second, a quinonediimine-type dica-

tion. The first oxidation at E1/2 ¼ 0.69 V for PAI 4c could be

assigned to electron loss from the nitrogen atom in the pendent

4,40-di-tert-butyldiphenylamine unit, which is more electron-rich

than the nitrogen atom on the main-chain amino group. The

highly stable redox stability of this polymer can be attributed to

the presence of tert-butyl group on the active sites of the TPPA

moiety. It is well known that triarylamines with substituents in

Fig. 3 Cyclic voltammograms of (a) ferrocene and the cast films of (b)

PAI 4c and (c) PAI 40c on the ITO-coated glass substrate in 0.1 M

Bu4NClO4/CH3CN at a scan rate of 100 mV s�1.


their para-position generally show reversible one-electron

oxidation behavior.19

The CV curve of PAI 4f is illustrated in Fig. 4, where those of

PAIs 4c and 40c are also included for comparison. PAI 4f exhibits

three redox amino centers in each repeat unit and shows three

corresponding quasireversible anodic redox couples. The second

oxidation at E1/2 ¼ 0.89 V appears to involve one electron loss

from the triphenylamine unit between the amide linkages. The

first (E1/2¼ 0.69 V) and third (E1/2¼ 1.05 V) oxidation waves are

related to the electron losses from the electroactive TPPA unit of

4f. These potentials are similar to those associated with mono-

cation and dication formations from the TPPA unit in PAI 4c.

Therefore, a possible anodic oxidation pathway of PAI 4f is

proposed as shown in Scheme S1 (ESI).† The electrochemical

stability of PAI 4f could also be ascribed to the fact that all the

electrochemically active sites of the arylamino unit are blocked

with tert-butyl groups.

Fig. 5 compares the cyclic voltammograms and differential

pulse voltammograms of PAI 4g and structurally related PAIs 4c

and 40 0c. PAIs 4c and 400c, which have isomeric repeating units

with the TPPA unit in different segments, each revealed two

well-resolved, reversible redox couples in their CV diagrams,

corresponding to two sequential electron removals from the

electroactive TPPA unit in their polymer backbones. The onset

potentials of the oxidative processes of PAI 40 0c are lower than

those of PAI 4c. This can be rationalized because the TPPA

segment is incorporated in the amide portion in the former case.

Therefore, the amino units became more easily oxidized. PAI 4g

also shows two apparent redox couples. However, the peak is

Fig. 4 Cyclic voltammograms of (a) ferrocene and (b) the cast films of

PAIs 40c, 4c and 4f on the ITO-coated glass substrate in 0.1 M Bu4NClO4/

CH3CN at a scan rate of 50 mV s�1.

Polym. Chem., 2010, 1, 1013–1023 | 1019

Fig. 5 (a) Cyclic voltammograms and (b) differential pulse voltammograms of the cast films of PAIs 4c, 40 0c and 4g on the ITO-coated glass substrate in

0.1 M Bu4NClO4/CH3CN solution. Scan rate, 50 mV s�1; pulse amplitude, 50 mV; pulse width, 50 ms; pulse period, 0.2 s.

Fig. 6 The 3-D spectroelectrochemical behavior of a PAI 4c thin film on

the ITO-coated glass substrate (in CH3CN containing 0.1 M Bu4NClO4

as the supporting electrolyte) between 0 and 1.3 V. The photo shows the

color change of the film on an ITO electrode at indicated potentials.

broader than that of PAIs 4c and 40 0c due to close overlapping of

the redox waves. From the differential pulse voltammograms of

4g, we can find three separate oxidation peaks at 0.65, 1.0, and

1.2 V, together with a shoulder around 0.75 V. Therefore, we

propose a possible four-step reaction sequence for the electro-

chemical oxidation of PAI 4g as shown in Scheme S2 (ESI).† The

E1/2 values of these four oxidations are estimated to be 0.63, 0.69,

0.95, and 1,04 V, respectively. However, the first two oxidations

occurred almost simultaneously by a two-electron loss event.

Therefore, the two oxidation waves merged and became indis-

tinguishable in the CV curve. Similar two-electron oxidation

event also occurred in the latter two oxidation processes.

The HOMO (highest occupied molecular orbital) energy levels

of the investigated PAIs were calculated from the oxidation onset

potentials (Eonset) or half-wave potentials of the first oxidation

wave (E1/2ox1) and by comparison with ferrocene (4.8 eV).20 These

data together with absorption spectra were then used to obtain

the LUMO (lowest unoccupied molecular orbital) energy levels

(Table 3). According to the HOMO and LUMO energy levels

obtained, the PAIs in this study appear to be appropriate as hole

injection and transport materials.

Spectroelectrochemical and electrochromic properties

The electro-optical properties of the polymer films were investi-

gated using the changes in electronic absorption spectra under

1020 | Polym. Chem., 2010, 1, 1013–1023

a voltage pulse. The electrode preparations and solution condi-

tions were identical to those used in the CV experiments. In the

following study, we first examined the spectral change of PAI 4c


Fig. 8 The spectral change and electrochromic behavior of PAI 4g thin

film on the ITO-coated glass slide (in CH3CN containing 0.1 M Bu4N-

ClO4 as the supporting electrolyte) at various electrode potentials (vs. Ag/

AgCl).

film (Fig. 6) during electrochemical oxidation. In the neutral

state, PAI 4c exhibited strong absorption at wavelength around

313 nm, characteristic for triarylamine p–p* transitions, but it

was almost transparent in the visible and near infrared (NIR)

regions. When the applied potential was gradually raised from

0.8 to 1.0 V, the absorption intensity at 313 nm slightly dropped

and a new shoulder band appeared at 411 nm accompanied with

a broad band having its maximum around 922 nm in the NIR

region. We attribute this spectral change to the formation of

a stable monocation radical from the TPPA moiety. The

absorption band in the NIR region is assigned to an intervalence

charge-transfer (IV-CT) between states in which the positive

charge is centered at different amino centers.13,21 The intensity of

the IV-CT band gradually decreased when the TPPA radical

cation was further oxidized to the dication (at electrode potential

of 1.3 V), with a formation of a new strong absorption band

centered at about 698 nm. The observed absorption changes of

the film of PAI 4c are fully reversible and are associated with

strong color changes. From the photos shown in Fig. 6, it can be

seen that the film switches from a transmissive neutral state

(nearly colorless) to a highly absorbing semioxidized state

(yellow) and a fully oxidized state (blue).

Next, PAIs 4f and 4g were examined. Their spectral changes

upon oxidation are illustrated in Fig. 7 and 8, respectively. In the

neutral state, these two PAIs revealed an absorption tail in the

region of 400–550 nm in addition to the strong p–p* transition

bands at 313 nm. Therefore, in the neutral state their films

exhibited a pale yellow color, not completely colorless. The

absorption tail may be accounted for a stronger interchain

charge-transfer interaction between the arylamino donor

(between the amide groups) and the trimellitimido acceptor.

Similar to that observed for PAI 4c, as the applied potential was

raised to 0.8 V PAI 4f showed a decrease in absorption at 313 nm

with a concomitant appearance of a peak at 411 nm and a broad

IV-CT band centered around 922 nm. This spectral change

corresponds to the first oxidation process of 4f as shown in

Fig. 7 The spectral change and electrochromic behavior of PAI 4f thin

film on the ITO-coated glass slide in 0.1 M Bu4NClO4/CH3CN at various

applied potentials (vs. Ag/AgCl).


Scheme S1.† When the electrode potential was adjusted to 1.0 V,

another absorption band appeared at 792 nm and the strong IV-

CT band at the NIR region still could be observed. This clearly

provides evidence that the second oxidation originates from the

triphenylamine core between the amide groups in the 4f main

chain. We believe that the polymer has been oxidized to one with

the bis(radical cation) repeating unit as the third structure shown

in Scheme S1.† When the applied potential was set at 1.3 V,

a strong absorption band in the 450–900 nm region centering at

around 685 nm was observed, whereas the intensity of the

absorption peak at 411 nm and the IV-CT band gradually

decreased. The almost disappearance of the IV-CT absorption

indicates the full oxidation of all the three amino centers in the

repeat unit of 4f. As can be seen from the inset in Fig. 7, the film

of PAI 4f displayed multi-electrochromic behavior with colora-

tion change from pale yellow to yellowish green, green, and blue

along with increasing of the applied potential.

A similar spectral change was observed for PAI 4g at early

stage of oxidation (Fig. 8). The absorption peak at 416 nm and

the IV-CT band at 997 nm started to appear when the applied

potential was set at 0.8 V and reached the maximum when the

applied potential was raised to 1.0 V. This result illustrated that

the first two oxidations of the TPPA units occurred almost

simultaneously. Although the oxidation waves could not be well-

resolved in the CV analysis for the third and fourth oxidations,

the stepwise oxidation processes were clearly evidenced by the

spectroelectrochemistry experiments. Further increase of the

applied potential over 1.0 V led to the increase of the absorption

intensity between 600 and 850 nm. This absorption change

indicated the occurrence of the third oxidation. Upon further

oxidation, the absorption band at 416 nm reached the minimum

intensity and the band at 500–800 nm further intensified. It was

also found that the IV-CT band at the NIR region diminished

gradually, implying the occurrence of the fourth oxidation.

When the polymer film of 4g was oxidized, its color changed

from pale yellow to deeper yellow, yellowish green, greenish blue,

Polym. Chem., 2010, 1, 1013–1023 | 1021

Table 4 Coloration efficiency with optical and electrochemical data ofPAI 4c

Cyclesa DOD922b Qc/mC cm�2 hd/cm2 C�1 Decay (%)e

1 0.322 1.20 268 010 0.321 1.25 257 4.120 0.319 1.24 257 4.130 0.317 1.24 256 4.540 0.315 1.23 256 4.550 0.312 1.22 256 4.560 0.310 1.21 256 4.570 0.310 1.21 256 4.580 0.309 1.21 255 4.990 0.307 1.20 255 4.9100 0.305 1.19 255 4.9

a Times of cyclic scan by applying potential steps between 0 V and 1.0 V(vs. Ag/AgCl). b Optical density change at 922 nm. c Ejected charge,determined from the in situ experiments. d Coloration efficiency is

e

and blue, as can be seen from the inset of Fig. 8. The results

supported the proposed mechanisms in the oxidative processes of

PAI 4g (Scheme S2, ESI†).

For electrochromic switching studies, the polymer film of 4c

was cast onto an ITO-coated glass slide in the same manner as

described earlier, and the film was potential stepped between its

neutral (0 V) and oxidized states (+ 1.0 or 1.3 V). While the

potential was switched, the absorbance at 411, 681 and 922 nm

was monitored as a function of time with UV-vis-NIR spec-

troscopy. Fig. 9 and 10 depict the stability and the switching

behavior of the polymer for the oxidative process. The switching

time was calculated at 90% of the full switch because it is difficult

to perceive any further color change with naked eye beyond this

point. As illustrated in ESI Fig. S5,† thin film from PAI 4c

revealed switching times of 5.1 s for lmax ¼ 922 nm and 2.5 s for

bleaching, reflecting the different reaction rates between the

Fig. 10 (a) Current consumption and (b) electrochromic switching

between 0 and 1.3 V and optical absorbance change monitored at 413 and

681 nm for the cast film of PAI 4c on ITO-glass slide (active area�1 cm2)

in 0.1 M Bu4NClO4/CH3CN with a cycle time of 20 s.

derived from the equation: h ¼ DOD922/Q. Decay of colorationefficiency after various cyclic scans.

Fig. 9 (a) Current consumption and (b) electrochromic switching

between 0 and 1.0 V and optical absorbance change monitored at 411 and

922 nm for the cast film of PAI 4c on ITO-glass slide (active area�1 cm2)

in 0.1 M Bu4NClO4/CH3CN with a cycle time of 20 s.

1022 | Polym. Chem., 2010, 1, 1013–1023

neutral and oxidized forms of the film of 4c. When the potential

was switched between 0 and 1.3 V, thin film of PAI 4c would

require almost 3.7 s for coloration at 681 nm and 1.6 s for

bleaching. After over 100 cyclic scans between 0.0 and 1.0 V, the

polymer films still exhibited good electrochemical and electro-

chromic stability. Coloration efficiency (CE; h) was measured by

monitoring the amount of ejected charge (Q) as a function of the

change in optical density (DOD) of the polymer film.17 The

electrochromic coloration efficiencies (h ¼ DOD/Q) of the

polymer films of 4c after various switching cycles are summarized

in Table 4. The CE of PAI 4c is high, ranging from 268 cm2 C�1

for the first cycle to 255 cm2 C�1 for the 100th cycle. After

switching 100 times between 0 V and 1.0 V, the film of PAI 4c

only showed 4.9% decay on CE. Therefore, all these results

revealed that the present PAIs exhibit high redox stability and

good electrochromic performance.

Conclusions

The diimide-dicarboxylic acid 2 was synthesized as a new PAI

building block. A series of novel PAIs with N,N,N0,N0-tetra-

phenyl-1,4-phenylenediamine (TPPA) units were readily

prepared from 2 with various aromatic diamines via the phos-

phorylation polyamidation reaction. Because of the presence of

the bulky tert-butyl and three-dimensional TPPA unit, all the

polymers were amorphous, had good solubility in many polar

aprotic solvents, and exhibited excellent film-forming ability. In

addition to high Tg values and good thermal stability, all the

obtained PAIs also revealed good electrochemical and electro-

chromic stability and multicolor electrochromic behavior. After

long-term cyclic switching, the polymer films still preserved high

redox and electrochromic activity. The new materials described

here represent a novel entry to the polymeric electrochromics

that may find potential application in the fabrication of elec-

trochromic devices.

Acknowledgements

We thank the National Science Council of the Republic of China

for the financial support of this work.


References

1 (a) P. M. S. Monk, R. J. Mortimer and D. R. Rosseinsky,Electrochromism: Fundamentals and Applications, VCH, Weinheim,Germany, 1995; (b) R. J. Mortimer, Chem. Soc. Rev., 1997, 26, 147;(c) D. R. Rosseinsky and R. J. Montimer, Adv. Mater., 2001, 13,783; (d) P. M. S. Monk, R. J. Mortimer and D. R. Rosseinsky,Electrochromism and Electrochromic Devices, Cambridge UniversityPress, Cambridge, UK, 2007.

2 (a) J. P. Cronin, T. J. Gudgel, S. R. Kennedy, A. Agrawal andD. R. Uhlmann, Mater. Res., 1999, 2, 1; (b) D. Cummins,G. Boschloo, M. Ryan, D. Corr, S. Rao and D. Fitzmaurice, J.Phys. Chem. B, 2000, 104, 11449; (c) H. W. Heuer, R. Wehrmannand S. Kirchmeyer, Adv. Funct. Mater., 2002, 12, 89; (d)G. Sonmez, C. K. F. Shen, Y. Rubin and F. Wudl, Angew. Chem.,Int. Ed., 2004, 43, 1498; (e) R. J. Mortimer, A. L. Dyer andJ. R. Reynolds, Displays, 2006, 27, 2.

3 (a) L. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik andJ. R. Reynolds, Adv. Mater., 2000, 12, 481; (b) L. Groenendaal,G. Zotti, P. H. Aubert, S. M. Maybright and J. R. Reynolds, Adv.Mater., 2003, 15, 855; (c) R. M. Walczak and J. R. Reynolds, Adv.Mater., 2006, 18, 1121.

4 (a) G. Sonmez, H. Meng and F. Wudl, Chem. Mater., 2004, 16, 574;(b) G. Sonmez, H. B. Sonmez, C. K. F. Shen and F. Wudl, Adv.Mater., 2004, 16, 1905; (c) G. Sonmez and F. Wudl, J. Mater.Chem., 2005, 15, 20; (d) G. Sonmez, H. B. Sonmez, C. K. F. Shen,R. W. Jost, Y. Rubin and F. Wudl, Macromolecules, 2005, 38, 669.

5 (a) C. G. Wu, M. I. Lu, S. J. Chang and C. S. Wei, Adv. Funct. Mater.,2007, 17, 1063; (b) A. Durmus, G. E. Gunbas and L. Toppare, Chem.Mater., 2007, 19, 6247; (c) G. E. Gunbas, A. Durmus and L. Toppare,Adv. Mater., 2008, 20, 691; (d) A. Cihaner and F. Algi, Adv. Funct.Mater., 2008, 18, 3583; (e) F. Algi and A. Cihaner, Org. Electron.,2009, 10, 704; (f) M. Pamuk, S. Tirkes, A. Cihaner and F. Algi,Polymer, 2010, 51, 62.

6 (a) S. H. Cheng, S. H. Hsiao, T. H. Su and G. S. Liou,Macromolecules, 2005, 38, 307; (b) G. S. Liou, S. H. Hsiao andH. W. Chen, J. Mater. Chem., 2006, 16, 1831; (c) S. H. Hsiao,Y. M. Chang, H. W. Chen and G. S. Liou, J. Polym. Sci., Part A:Polym. Chem., 2006, 44, 4579; (d) C. W. Chang, S. H. Hsiao andG. S. Liou, J. Mater. Chem., 2007, 17, 1007; (e) S. H. Hsiao,G. S. Liou, Y. C. Kung and H. J. Yen, Macromolecules, 2008, 41,2800; (f) Y. C. Kung, G. S. Liou and S. H. Hsiao, J. Polym. Sci.,Part A: Polym. Chem., 2009, 47, 1740.

7 Y. Imai, in Synthesis of Polyamideimides in Polyimide: Fundamentalsand Applications, ed. M. K. Ghosh and K. L. Mittal, Marcel Dekker,New York, 1996, pp. 49–70.

8 (a) N. Yamazaki, M. Matsumoto and F. Higashi, J. Polym. Sci.,Polym. Chem. Ed., 1975, 13, 1373; (b) F. Higashi, S. Ogata and


Y. Aoki, J. Polym. Sci., Polym. Chem. Ed., 1982, 20, 2081; (c)W. R. Krigbaum, R. Kotek, Y. Mihara and J. Preston, J. Polym.Sci., Polym. Chem. Ed., 1985, 23, 1907.

9 (a) C. P. Yang and S. H. Hsiao, Makromol. Chem., 1989, 190, 2119;(b) S. H. Hsiao and C. P. Yang, J. Polym. Sci., Part A: Polym.Chem., 1990, 28, 1149; (c) S. H. Hsiao and C. P. Yang, Makromol.Chem., 1990, 191, 155.

10 (a) W. Wrasidlo and J. M. Augl, J. Polym. Sci., Part A-1: Polym.Chem., 1969, 7, 321; (b) W. Wrasidlo and J. M. Augl, J. Polym.Sci., Part A-1: Polym. Chem., 1969, 7, 1589; (c) J. L. Nieto, J. G. dela Campa and J. de Abajo, Makromol. Chem., 1982, 183, 557; (d)J. G. de la Campa, J. de Abajo and J. L. Nieto, Makromol. Chem.,1982, 183, 571.

11 (a) S. H. Hsiao, C. P. Yang, C. W. Chen and G. S. Liou, Eur. Polym.J., 2005, 41, 511; (b) C. P. Yang, Y. P. Chen and E. M. Woo, J. Appl.Polym. Sci., 2006, 101, 2854; (c) Y. T. Chern, C. M. Huang andS. C. Huang, Polymer, 1998, 39, 2929; (d) D. J. Liaw, P. N. Hsu,W. H. Chen and B. Y. Liaw, Macromol. Chem. Phys., 2001, 202,1483; (e) H. Behniafar and A. Banihashemi, Eur. Polym. J., 2004,40, 1409; (f) C. Lee, N. P. Iyer, K. Min, H. Pak and H. Han, J.Polym. Sci., Part A: Polym. Chem., 2004, 42, 137.

12 K. Y. Chiu, T. H. Su, C. W. Huang, G. S. Liou and S. H. Cheng, J.Electroanal. Chem., 2005, 578, 283.

13 C. Lambert and G. Noll, J. Am. Chem. Soc., 1999, 121, 8434.14 (a) G. S. Liou and C. W. Chang, Macromolecules, 2008, 41, 1667; (b)

C. W. Chang and G. S. Liou, J. Mater. Chem., 2008, 18, 5638; (c)C. W. Chang, C. H. Chung and G. S. Liou, Macromolecules, 2008,41, 8441; (d) H. J. Yen and G. S. Liou, Chem. Mater., 2009, 21, 4062.

15 S. H. Hsiao, G. S. Liou and H. M. Wang, J. Polym. Sci., Part A:Polym. Chem., 2009, 47, 2330.

16 C. P. Yang, R. S. Chen and K. H. Chen, Colloid Polym. Sci., 2003,281, 505.

17 (a) C. L. Gaupp, D. M. Welsh, R. D. Rauh and J. R. Reynolds, Chem.Mater., 2002, 14, 3964; (b) R. J. Mortimer and J. R. Reynolds, J.Mater. Chem., 2005, 15, 2226.

18 J. N. Demas and G. A. Crosby, J. Phys. Chem., 1971, 75, 991.19 (a) E. T. Seo, R. F. Nelson, J. M. Fritsch, L. S. Marcoux, D. W. Leedy

and R. N. Adams, J. Am. Chem. Soc., 1966, 88, 3498; (b) R. F. Nelsonand R. N. Adams, J. Am. Chem. Soc., 1968, 90, 3925; (c) H. Zhao,C. Tanjutco and S. Thayumanavan, Tetrahedron Lett., 2001, 42,4421; (d) S. Amthor, B. Noller and C. Lambert, Chem. Phys., 2005,316, 141.

20 J. Y. Shen, C. Y. Lee, T. H. Huang, J. T. Lin, Y. T. Tao, C. H. Chienand C. Tsai, J. Mater. Chem., 2005, 15, 2455.

21 (a) C. Lambert and G. Noll, Angew. Chem., Int. Ed., 1998, 37, 2107;(b) C. Lambert and G. Noll, Synth. Met., 2003, 139, 57; (c)C. C. Chiang, H. C. Chen, C. S. Lee, M. K. Leung, K. R. Lin andK. H. Hsieh, Chem. Mater., 2008, 20, 540.

Polym. Chem., 2010, 1, 1013–1023 | 1023

Supplementary Material (ESI) for Polymer Chemistry This journal is (c) The Royal Society of Chemistry 2010

Supplementary Information

Multicolor electrochromic poly(amide-imide)s with N,N-diphenyl- N’,N’-di-4-tert-butylphenyl-1,4-phenylenediamine moieties

Hui-Min Wang and Sheng-Huei Hsiao*

Department of Chemical Engineering and Biotechnology, National Taipei University

of Technology, 1 Chung-Hsiao East Road, Section 3, 10608 Taipei, Taiwan

Tel: +886-2-27712171#2548; Fax: + 886-2-27317117; E-mail: [email protected]

List of Contents for Supplementary Material:

Scheme S1 Anodic oxidation pathways of PAI 4f.

Scheme S2 Anodic oxidation pathways of PAI 4g.

Fig. S1 IR spectrum of the diimide-diacid 2 and PAI 4a.

Fig. S2 (a) H-H COSY and (b) C-H HMQC spectra of diimide-diacid 2 in DMSO-d6.

Fig. S3 1H NMR spectra of PAI 4c in DMSO-d6.

Fig. S4 WAXD patterns of PAI films 4a-4g.

Fig. S5 Calculation of optical switching time at (a) 922 nm and (b) 681 nm at the

applied potential of PAI 4c thin film on the ITO-coated glass substrate in 0.1 M

Bu4NClO4/CH3CN.

2

Scheme S1 Anodic oxidation pathways of PAI 4f.

nN

N

NO

O

N

HN

OC N

HCO

N

O

O

nN

N

NO

O

N

HN

OC N

HCO

N

O

O

nN

N

NO

O

N

HN

OC N

HCO

N

O

O

n

N

O

O

N

OC

HNC

ONH

N

O

ON

N

- e-+ e-

- e-+ e-

- e-+ e-

E1/2 = 0.69 V

E1/2 = 0.89 V

E1/2 = 1.05 V

3

Scheme S2 Anodic oxidation pathways of PAI 4g.

n

N

N

O

O

HN

O

O

N

HN

OC

NN

N

OC

n

N

CO

NN

CO

NH

N

O

O

NH

O

O

N

N

- e-+ e-

- e-+ e-

CO

N

NN

CO

NH

N

O

O

NH

O

O

N

N

n

n

CO

N

NN

CO

NH

N

O

O

NH

O

O

N

N

n

CO

N

NN

CO

NH

N

O

O

NH

O

O

N

N

+ e- - e-

- e-+ e-

E1/2 = 0.69 V

E1/2 = 0.95 V

E1/2 = 0.63 V

E1/2 = 1.04 V

4

Fig. S1 IR spectrum of the diimide-diacid 2 and PAI 4a.

N

N

HOOCO

O

N

O

O

NCOOH

n

CO O

O

N

N

N

O

O

N

HN

OC

HN

5

Fig. S2 (a) H-H COSY and (b) C-H HMQC spectra of diimide-diacid 2 in DMSO-d6.

1

23

456

78

910

11 1213

1415 16

17

18

19202122

ab

c

d

ef

g

hi

N

N

O

OHOOC

N

O

O

NCOOH

6

Fig. S3 1H NMR spectrum of PAI 4c in DMSO-d6.

Fig. S4 WAXD patterns of thin films of PAIs 4a-4g.

ab

c

de

fhi

n

g

N

N

ON

O

O

HN

OC N

H

O

O

N

OC

7

Fig. S5 Calculation of optical switching time at (a) 922 nm and (b) 681 nm at the applied potential of PAI 4c thin film on the ITO-coated glass substrate in 0.1 M Bu4NClO4/CH3CN.

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Multicolor electrochromic poly(amide-imide)s with N,N