macromol-1

Synthesis, Optical, and Electrochemical Properties of the

High-Molecular-Weight Conjugated Polycarbazoles

Yaqin Fu, Zhishan Bo*

State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences,Beijing 100080, ChinaFax: (86) 10 82618587; E-mail: [email protected]

Received: July 7, 2005; Revised: August 24, 2005; Accepted: August 29, 2005; DOI: 10.1002/marc.200500478

Keywords: chain; high molecular weight; poly(2,7-carbazole)s; Suzuki polycondensation; synthesis

Introduction

The recent development of conjugated polymers has

received much attention because of their potential applica-

tions in light-emitting diodes (LEDs),[1] solar cells,[2]

sensors,[3] etc. Interest in the carbazole-based conjugated

polymers and oligomers arises mainly from their useful

applications as photoconductors,[4,5] photorefractive mate-

rials,[4,5] hole-transporting materials,[6] light-emitting

materials,[7] and host materials for triplet emitters.[8] Many

attempts have been devoted to synthesize carbazole-based

polymers, and most polymers are based on the 3,6-

linkage.[9,10] For example, Iraqi and Wataru reported the

preparation of 3,6-linked carbazole polymers by coupling

ofN-alkyl-3,6-dihalocarbazole (Br and I) in the presence of

magnesium and (2,2-bipydine)dichloro palladium.[9b] The

number-average molecular weight of the polymers was in

the range of 25 kDa. Strohriegl and colleagues have

reported that a limiting factor in the synthesis of high-

molecular-weight poly(N-alkyl-3,6-carbazole)s is the for-

mation of low-molar-mass cyclic oligomers.[10] Recently,

Li et al. reported the synthesis and light-emitting properties

of random and alternating fluorine carbazole polymers,[11]

Zhang et al. have successfully prepared the high-molecular-

weight poly(N-alkyl-3,6-carbazole)s and the optically

active poly(3,6-carbazole)s by using a reverse addition

order for the zerovalent nickel reagent based on the

Yamamoto coupling reaction.[12] Carbazole polymers

Summary: A kind of novel dibromocarbazole monomerbearing three alkyl chains was prepared. Two strategies weredeveloped to improve the solubility and molecular weight ofcarbazole polymers. One was the polymerization of N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carba-zole with the alkylated dibromocarbazole. Another one wasthe polymerization of N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carbazole with N-octyl-3,6-dibro-mocarbazole. All the polymerizations were carried out underpalladium-catalyzed Suzuki polycondensation (SPC) con-ditions. Through using carbazole monomer bearing threealkyl chains to polymerize, we have successfully boosted thenumber-average molecular weight of 2,7-linked carbazolepolymers from not more than 5 to 67 kDa. The high-molecular-weight polymers were obtained in high yields anddisplayed good solubility in common organic solvents. Theiroptical, electrochemical, and thermal properties were alsoreported.

Preparation of carbazole polymers by Suzuki polycondensa-tion.

Macromol. Rapid Commun. 2005, 26, 17041710 DOI: 10.1002/marc.200500478 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1704 Communication

based on 2,7-linkage have received particular attention

because they could offer a higher degree of conjugation than

the polymers based on the 3,6-linkage. The first 2,7-

carbazole homopolymers and copolymers were prepared by

Morin and Leclerc using Yamamoto coupling, Suzuki

coupling, and Stille coupling.[13] The 2,7-carbazole homo-

polymers obtained by Yamamoto coupling method were

only partially soluble in common organic solvents, such as

chloroform and THF. The number-average molecular

weight [measured by gel permeation chromatography

(GPC) against polystyrene standards] of the soluble part

was about 5 kDa with a polydispersity of around 1.5.

Poly(N-octyl-2,7-carbazole-alt-9,9-dioctyl-2,7-fluorene)s

prepared by Suzuki coupling were soluble in the above-

mentioned organic solvents, but their number-average

molecular weight was also around 5 kDa. Using similar

method, Iraqi et al. synthesized 2,7-linked carbazole

polymers with the number-average molecular weight in

the range from 2 to 5 kDa. In order to improve the molecular

weight of 2,7-linked carbazole polymers, Morin and

Leclerc[7] used the reverse addition method suggested by

Zhang et al. in the synthesis, but this method did not lead to

any increase of the molecular weight.

In this communication, we report two strategies to

synthesize high-molecular-weight soluble conjugated car-

bazole polymers. Novel 2,7-dibromocarbazole monomer

bearing three alkyl chains was synthesized and used to

polymerize with N-octyl-2,7-carbazolediboronic pinacol

ester. The introduction of alkyl chains onto carbazole ring

could significantly improve the solubility of the 2,7-linked

carbazole polymers in common organic solvents and the

number-average molecular weight. The polymerization of

N-octyl-2,7-carbazolediboronic pinacol ester with N-octyl-

3,6-dibromocarbazole could also give soluble high-molec-

ular-weight polymers. Suzuki polycondensation (SPC) was

used to polymerize these monomers, and the influence of

the structure of monomers on the molecular weight of

polymers was investigated. In addition, the optical, electro-

chemical, and thermal properties of the carbazole polymers

were also reported.

Experimental Part

4-Bromo-1-iodo-2-nitrobenzene,[14] 4-bromo-2,5-di-n-hexyl-benzeneboronic acid,[15] N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carbazole,[16] N-octyl-3,6-dibromo-carbazole,[11] N-octyl-3,6-bis(4,4,5,5-tetramethyl-1,3,2-diox-aborolan-2-yl)carbazole,[11] poly(N-octyl-3,6-carbazole),[17]

and poly(N-octyl-2,7-carbazole) (5)[7] were synthesizedaccording to the literature procedures. All the chemicals werepurchased from Acros and used as received. The 1H and 13CNMR spectra were recorded on an AV400 or DM300spectrometer in CDCl3. The GPC measurements wereperformed on Waters 410 system against polystyrene standardswith THF as an eluent. UV-visible absorption spectra wereobtained on a SHIMADZU UV-visible spectrometer model

UV-1601PC. Fluorescence emission spectra were recorded inTHF at 293 K with a HITACHI F4500 fluorescence spectro-photometer. Fluorescence quantum yields (FF) of the samplesin toluene were measured by using 9,10-diphenylanthracene(FF 0.9 in toluene) as standard. The electrochemicalexperiments were performed on CHI 630A ElectrochemicalAnalyzer in acetonitrile at a glassy carbon or ITO glassworking electrode in a three-electrode cell with a Pt wirecounter electrode and an Ag/Ag reference electrode. Thefilms on the work electrodes for cyclic voltammetry (CV)investigation were deposited by casting from chloroformsolution.

4-Bromo-2-nitro-20,50-di-n-hexyl-40-bromobiphenyl (1)

A mixture of 4-bromo-1-iodo-2-nitrobenzene (4.8 g,14.7 mmol), 4-bromo-2,5-dihexylphenylboronic acid (5.0 g,13.4 mmol), NaHCO3 (15 g, 0.12 mol), THF (115 mL), andH2O (45 mL) was degassed and Pd(PPh3)4 (0.15 g, 0.13 mmol)was added under nitrogen atmosphere. The reaction mixturewas heated at 50 8C and stirred under nitrogen for 6 d. CH2Cl2(200 mL) and H2O (50 mL) were added to dissolve the formedprecipitate. The organic layer was separated, the aqueous oneextracted with CH2Cl2 (3), and the combined organic phasedried over Na2SO4. After removal of the solvent, the crudeproduct was purified by flash column chromatography elutingwith petroleum ether to afford compound 1 as a yellow oil(4.5 g, 66%).

1H NMR (400 MHz, CDCl3): d 8.13 (s, 1H), 7.73 (d, 1H,J 8.7 Hz), 7.44 (s, 1H), 7.19 (d, 1H, J 8.2 Hz), 6.86 (s, 1H),2.67 (t, 2H, J 7.8 Hz), 2.31 (m, 2H), 1.53 (m, 2H), 1.32(m, 2H), 1.29 (m, 6H), 1.14 (m, 6H), 0.85 (m, 6H).

13C NMR (75 MHz, CDCl3): d 149.3, 139.5, 135.4, 135.1,134.4, 133.6, 133.1, 129.9, 127.2, 124.6, 121.6, 35.6, 32.6,31.6, 31.4, 30.3, 29.7, 29.1, 22.6, 22.4, 14.0.

Anal. Calcd. for C24H31Br2NO2: C 54.87, H 5.95, N 2.67;Found: C 55.18, H 6.04, N, 2.35.

2,7-Dibromo-1,4-dihexylcarbazole (2)

A mixture of 1 (1.5 g, 2.9 mmol) and triethylphosphite (20 mL)was heated to reflux and stirred at nitrogen atmosphere for 24 h.The excess of triethylphosphite was removed under reducedpressure and the crude product was purified by flash columnchromatography eluting with CH2Cl2/petroleum ether (1:2) toprovide 2 as a white solid (0.6 g, 43%). m.p. 120121 8C.

1H NMR (300 MHz, CDCl3): d 8.06 (s, 1H), 7.86 (d, 1H,J 8.4 Hz), 7.62 (s, 1H), 7.37 (d, 1H, J 8.0 Hz), 7.22 (s, 1H),3.08 (t, 2H, J 7.8 Hz), 2.97 (t, 2H, J 8.0 Hz), 1.75 (m, 2H),1.66 (m, 2H), 1.47 (m, 6H), 1.35 (m, 6H), 0.88 (m, 6H).

13C NMR (100 MHz, CDCl3): d 140.2, 139.2, 137.1,124.7, 123.5, 123.1, 122.5, 122.0, 121.5, 119.8, 118.9, 113.7,33.8, 31.8, 31.3, 29.5, 29.4, 28.9, 22.7, 22.6, 14.1.

Anal. Calcd. for C24H31Br2N: C 58.43, H 6.33, N 2.84;Found: C 58.50, H 6.40, N 2.87.

2,7-Dibromo-1,4-dihexyl-N-octylcarbazole (3)

Compound 3 was prepared as a white solid in a yield of 87%according to the literature procedures.[18] m.p. 5758 8C.

Synthesis, Optical, and Electrochemical Properties of the High-Molecular-Weight Conjugated Polycarbazoles 1705

Macromol. Rapid Commun. 2005, 26, 17041710 www.mrc-journal.de 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1H NMR (400 MHz, CDCl3): d 7.89 (d, 2H, J 8.4 Hz),7.54 (s, 1H), 7.35 (d, 1H, J 8.3 Hz), 7.27 (s, 1H), 4.32 (t, 2H,J 8.1 Hz), 3.15 (t, 2H, J 8.2 Hz), 3.08 (t, 2H, J 7.8 Hz),1.80 (m, 4H), 1.67 (m, 2H), 1.521.30 (m, 22H), 1.00 (m, 9H).

13C NMR (100 MHz, CDCl3): d 142.21, 139.15, 136.90,125.01, 124.11, 123.50, 122.51, 122.32, 121.49, 120.89,119.00, 111.94, 45.22, 33.84, 31.87, 31.74, 31.72, 31.60,30.74, 30.10, 29.45, 29.41, 29.27, 29.21, 29.16, 26.84, 22.67,22.61, 14.07, 14.05.

Anal. Calcd. for C32H47Br2N: C 63.47, H 7.82, N 2.31;Found: C 63.48, H 7.87, N 2.37.

Polymer 6

A mixture of N-octyl-3,6-dibromocarbazole (0.08 g,0.19 mmol), N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxa-borolan-2-yl)carbazole (0.1 g, 0.19 mmol), NaHCO3 (0.4 g,4.8 mmol), THF (15 mL), and H2O (4 mL) was degassed andPd(PPh3)4 (4 mg, 0.003 mmol) was added under nitrogenatmosphere. The reaction mixture was heated at reflux andstirred under nitrogen for 48 h. The formed precipitate wascollected by filtration, dissolved in THF, and filtered through ashort pad of silica gel column eluting with THF. The filtrate wasconcentrated to 5 mL, precipitated into methanol (50 mL), theformed precipitate collected by filtration, and dried undervacuum to give 6 (0.09 g, 82%) as a yellow solid.

1H NMR (300 MHz, CDCl3): d 8.55 (broad, 2H), 8.198.15 (broad, 2H), 7.88 (broad, 2H), 7.73 (broad, 2H), 7.667.60 (broad, 2H), 7.527.47 (broad, 2H), 4.474.30 (broad,4H), 1.96 (broad, 4H), 1.461.23 (broad, 20H), 0.880.78(broad, 6H).

13C NMR (75 MHz, CDCl3): d 141.6, 140.3, 139.9, 133.5,125.9, 123.6, 121.4, 120.5, 119.4, 119.0, 109.1, 107.3, 43.4,31.8, 29.4, 29.2, 27.4, 22.6, 14.0, 1.0.

Anal. Calcd for [C40H46N2]n: C 86.59, H 8.36, N 5.05;Found: C 83.91, H 8.27, N 5.00.

Polymer 7

A mixture of compound 3 (0.12 g, 0.19 mmol), N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carbazole(0.1 g, 0.19 mmol), NaHCO3 (0.4 g, 4.8 mmol), THF (15 mL),and H2O (4 mL) was degassed and Pd(PPh3)4 (4 mg,0.003 mmol) was added under nitrogen atmosphere. The reac-tion mixture was heated at reflux and stirred under nitrogen for3 d. The formed precipitate was collected by filtration, dissol-ved in THF, and filtered through a short pad of silica gel columneluting with THF. The filtrate was concentrated to 5 mL,precipitated into methanol (50 mL), the formed precipitatecollected by filtration, and dried under vacuum to give7 (0.12 g,87%) as a yellow solid.

1H NMR (300 MHz, CDCl3): d 8.288.19 (broad, 3H),7.797.68 (broad, 4H), 7.517.47 (broad, 1H), 7.337.31(broad, 1H), 7.09 (broad, 1H), 4.564.47 (broad, 4H), 3.293.00 (broad, 4H), 2.031.61 (broad, 6H), 1.401.16 (broad,34H), 0.950.75 (broad, 12H).

13C NMR (75 MHz, CDCl3): d 142.0, 141.2, 140.4, 138.9,134.6, 120.9, 120.8, 118.8, 110.0, 107.7, 31.4, 31.1, 29.3, 29.0,28.9, 27.1, 26.6, 22.3, 22.2, 22.1, 13.7, 13.5.

Anal. Calcd. for [C52H70N2]n: C 86.37, H 9.76, N 3.87;Found: C 82.98, H 9.61, N 3.82.

Results and Discussion

Monomer Synthesis

The synthetic route leading to carbazole monomer bearing

alkyl chains is outlined in Scheme 1. Starting from

commercially available 4-bromo-1-iodo-2-nitrobenzene,

its coupling with 4-bromo-2,5-dihexylphenylboronic acid

in a biphasic mixture of THF and aq. NaHCO3 with

Pd(PPh3)4 as the catalyst precursor gave 1 in a yield of 66%.A reductive Cadogan ring closure of 1 via refluxing withP(OEt)3 gave carbazole 2 in a 43% yield. Following aprocedure suggested by Leclerc and colleagues, alkylation

of the N-position was achieved.[13] Monomer 3, whichexhibited very good solubility in common organic solvents,

was obtained in a yield of 87%. The purity of 3 wasconfirmed by 1H and 13C NMR spectroscopy and elemental

analysis.

Synthesis and Characterization of the Polymers

Scheme 1 depicts the synthetic route to the carbazole

polymers 47. Palladium-catalyzed SPC was used toprepare the target polymers. In order to achieve high-

molecular-weight soluble carbazole polymers, we have

screened four groups of reactions. The preparation of 3,6-

linked and 2,7-linked carbazole polymers (4 and 5) has beenreported in the literature.[7,11] Here we used SPC to

synthesize these two polymers, as shown in Scheme 1.

Polymer 4 was prepared by SPC of N-octyl-3,6-dibromo-carbazole and N-octyl-3,6-bis(4,4,5,5-tetramethyl-1,3,2-

dioxaborolan-2-yl)carbazole and polymer 5 was preparedby SPC of N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-diox-

aborolan-2-yl)carbazole and N-octyl-2,7-dibromocarba-

zole. Both 4 and 5 we prepared were only partiallysoluble in common organic solvents, such as CH2Cl2,

CHCl3, and THF, and their molecular weights were also

relatively low (see Table 1). The polymerization ofN-octyl-

3,6-dibromocarbazole with N-octyl-2,7-bis(4,4,5,5-tetra-

methyl-1,3,2-dioxaborolan-2-yl)carbazole under the stan-

dard SPC conditions gave polymer 6 in a yield of 82%.Polymer 6 was fully soluble in common organic solventsmentioned above, and its number-average molecular

weight reached 14.9 kDa. According to the hair-rod model

suggested by Wegner et al.,[19] the introduction of flexible

alkyl chains on the carbazole ring should increase the

solubility of the corresponding polymers, and thus high-

molecular-weight polymers should be prepared. Coupling

of the alkylated carbazole monomer 3 with N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carbazole

gave polymer 7 in a yield of 87%. During the reaction,

1706 Y. Fu, Z. Bo


polymers 6 and 7 started to precipitate from the reactionsystem in about 10 and 5 h, respectively, but the formed

precipitates could be easily redissolved in pure THF.

Reprecipitation with methanol to remove the lower

molecular weight oligomers and freeze-drying from

benzene afforded the pure polymers 6 and 7 as amorphousyellow solids. The structures of polymers 6 and 7 were

proved by 1H and 13C NMR spectroscopy and combustion

analysis. For a comparison, the molecular weights and

polydispersities of polymers 47 are summarized inTable 1. The number-average molecular weight of polymer

7 was up to 67 kDa.

Optical Properties

Figure 1(a) shows the absorption and photoluminescence

spectra of polymers 57 in THF solution at roomtemperature. Polymer 5 absorbed in ultraviolet regionpeaked at about 384 nm. Polymer 6 showed a broaderabsorption band with the maximum at about 357 nm and

polymer 7 exhibited a narrower absorption band with theabsorption maximum at about 362 nm. Compared with

polymer 5, the absorption maxima of polymers 6 and 7

Scheme 1.

Table 1. Molecular weights, polydispersities, and fluorescencequantum yields of the polymers.

Polymer Mn Mw Mw=Mn FF

4 3 900 5 200 1.31 5 6 400 9 000 1.41 0.906 14 900 25 000 1.69 0.657 67 000 82 600 1.23 0.94



were blue-shifted for about 20 nm. In comparison with the

3,6-linked carbazole polymers,[5] the absorption maxima of

polymer 6 and 7 were significantly red-shifted. Theseresults indicated that the introduction of alkyl chains

onto carbazole rings or the polymerization with 3,6-linked

monomers could decrease the effective conjugation length

of the polymers to some extent. The reason for the

introduction of alkyl chains onto carbazole rings decreasing

the effective conjugation length was that the alkyl chains on

carbazole rings could lead to larger dihedral angles between

the carbazole rings. The effective conjugation length of the

four polymers was in the following order: polymer

4< polymer 6< polymer 7< polymer 5. In THF solution,polymer 6 exhibited an emission band in the blue regionwith one peak at 403 nm and one shoulder at 417 nm;

polymer 7 displayed an emission peak at 405 nm and ashoulder at 425 nm. Compared with the emission spectra of

polymer 5 in THF solution, a blue shift of 1214 nm wasobserved for the emission peaks of polymers 6 and 7. The

fluorescence quantum efficient yields (FF) of the polymersin toluene were measured with 9,10-diphenylanthracene as

a reference standard (toluene, FF 0.9, excited at 360 nm)and are summarized in Table 1. In dilute toluene solution,

polymer 7 exhibited a very high fluorescence quantumyield.

Solid films on quartz plates used for the optical

measurements were prepared by spin-coating with 1%

THF solution. Figure 1(b) shows the film absorption and

photoluminescence spectra of polymers 57. In contrast toits solution spectrum, the absorption band of polymer 5wasapparently broader and a long wavelength tail appeared. For

polymers 6 and 7, only slightly broadening and red shiftwere observed for their film absorption spectra. The

broadening and red shift of the film absorption spectra

indicated that there existed some aggregations or inter-

actions of the polymer chains in the solid state. Compared

with the solution emission spectra of polymers 57, a redshift was observed in their film ones. In film polymer 5displayed structural emission spectra with two peaks at 434

and 462 nm and a shoulder at around 492 nm. Polymers 6and 7 displayed structureless emission spectra peaked at414 and 418 nm, respectively. Compared with their solution

emission spectra, the emission maxima of polymers 6 and 7were red-shifted for about 12 nm. Polymers 6 and 7exhibited good thermal stability; no long-wavelength green

emission band was observed after their films (prepared by

spin-coating from toluene solution) were annealed at

120 8C in air for 5 h. In contrast, previous reports showedthat the annealing of polyfluorene film resulted in the

appearance of an additional emission band between 500 and

600 nm due to the formation of the ketonic defects. These

carbazole polymers showed promising results as blue light-

emitting materials.

The electrochemical behaviors of polymers 6 and 7wereinvestigated by using CV with a standard three-electrode

electrochemical cell in acetonitrile solution containing

0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6)

at room temperature. The oxidation potentials were measur-

ed versus Ag/AgNO3 as a reference electrode and a standard

ferrocene/ferrocenium redox system as the internal stand-

ard for estimating the HOMO of the polymer films. The

polymer films on the work electrodes were deposited by

casting from chloroform solution. The CV curves of

polymers 6 and 7 in film are shown in Figure 2 and 3,respectively. In the range of 01.2 V, the film of polymer 6displayed one oxidation peak at 0.76 V in the first redox

cycle. From the second redox cycle, the oxidation peak

shifted to a higher potential (0.89 V). The film exhibited

color and solubility changes accompanying the redox

process. The fresh yellow film became dark green and

insoluble in THF by increasing the applied potential up to

0.8 V. For polymer 7, the film showed one oxidation peak at0.86 V in the first redox cycle and no peak in the successive

cycles in the range of 01.3 V. Similar to polymer 6, the

Figure 1. Absorption and PL spectra (excited at 360 nm) ofpolymers 5, 6, and 7 in solution (a) and in films (b).

1708 Y. Fu, Z. Bo


yellow film of polymer 7 also turned dark green andinsoluble in THF by increasing the potential applied up to

1.1 V. The unstability of polymers 6 and 7was probably dueto that the 3,6-positions of the carbazole ring in 2,7-linked

carbazole polymers were highly activated and could form

the radical-cations of carbazolic units.[2022] The carbazole

polymers formed cross-linking structures during the CV

measurements.[23] Taking 4.8 eV as the HOMO level forthe ferrocene/ferrocenium redox system, HOMO level of

5.33 and 5.47 eV were calculated for polymers 6 and 7,respectively. The band gap (DE) of 6 and 7 calculated fromthe UV-vis absorption onset of the films were both 2.9 eV.

The LUMO levels of polymers 6 and 7 in film wereestimated to be 2.43 and 2.57 eV, respectively.

In conclusion, we have successfully synthesized two

kinds of novel carbazole polymers by using palladium-

catalyzed SPC. Through the introduction of flexible alkyl

chains onto carbazole rings, we have obtained in high yield

soluble 2,7-linked carbazole polymers and boosted their

number-average molecular weight to 67 kDa. Through the

polymerization of 2,7-linked carbazole monomers with 3,6-

linked monomers, we have obtained soluble carbazole

polymers with a number-average molecular weight of 14.9

kDa. Primary studies indicated that 2,7-linked carbazole

polymers bearing alkyl chains were good blue light-

emitting materials, which were of high PL quantum yield

(FF) and good thermal stability.

Acknowledgements: Financial support from the NationalNatural Science Foundation of China (No. 20225415, 20423003,and 20374053), and the Major State Basic Research DevelopmentProgram (No. 2002CB613401) is greatly acknowledged.

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Figure 2. The first, second, and third redox cycles of polymer6 film, measured at a scan rate of 0.1 V s1 versus Ag/Ag inacetonitrile with TBAPF6 as supporting electrolyte.

Figure 3. The first and second redox cycles of polymer 7 film,measured at a scan rate of 0.1 V s1 versus Ag/Ag in acetonitrilewith TBAPF6 as supporting electrolyte.



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