Synthesis and electroluminescence properties of white-light single polyfluorenes with high-molecular weight by click reaction

Article abstract of DOI:10.1002/pola.24772

We reported a new way to synthesize single-chain white light-emitting polyfluorene (WPF) with an increased molecular weight using azide-alkyne click reaction. Four basic polymers with specific end-capping, which exhibited high-glass transition temperatures (T_g > 100 °C) and excellent thermal stability, were used as foundations of the WPF's synthesis; a blue-light polymer (PFB2) end-capped with azide groups can easily react with acetylene end-capped polymers (PFB1, PFG1, and PFR1, which are emitting blue-, green- and red-light, respectively) to form triazole-ring linkages in polar solvents such as N,N-dimethylforamide/toluene co-solvent at moderate temperature of 100 °C, even without metal-catalyst. Several WPFs that consist of these four basic polymers in certain ratios were derived, and the polymer light-emitting diode device based on the high-molecular weight WPF was achieved and demonstrated a maximum brightness of 7551 cd/m² (at 12.5 V) and a maximum yield of 5.5 cd/A with Commission Internationale de l'Eclairage coordinates of (0.30, 0.33) using fine-tuned WPF5 as emitting material.

Full text of DOI:10.1002/pola.24772

Synthesis and Electroluminescence Properties of White-Light Single
Polyfluorenes with High-Molecular Weight by Click Reaction
CHIH-NAN LO, CHAIN-SHU HSU
Department of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan
Received 16 March 2011; accepted 9 May 2011
DOI: 10.1002/pola.24772
Published online 27 May 2011 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: We reported a new way to synthesize single-chain
white light-emitting polyfluorene (WPF) with an increased mo-
lecular weight using azide-alkyne click reaction. Four basic
polymers with specific end-capping, which exhibited high-glass
transition temperatures (Tg > 100 ꢀC) and excellent thermal sta-
bility, were used as foundations of the WPF’s synthesis; a blue-
light polymer (PFB2) end-capped with azide groups can easily
react with acetylene end-capped polymers (PFB1, PFG1, and
PFR1, which are emitting blue-, green- and red-light, respec-
tively) to form triazole-ring linkages in polar solvents such as
N,N-dimethylforamide/toluene co-solvent at moderate tempera-
ture of 100 ꢀC, even without metal-catalyst. Several WPFs that
consist of these four basic polymers in certain ratios were
derived, and the polymer light-emitting diode device based on
the high-molecular weight WPF was achieved and demon-
strated a maximum brightness of 7551 cd/m2 (at 12.5 V) and a
maximum yield of 5.5 cd/A with Commission Internationale de
l’Eclairage coordinates of (0.30, 0.33) using fine-tuned WPF5 as
C
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emitting material.
2011 Wiley Periodicals, Inc. J Polym Sci
Part A: Polym Chem 49: 3355–3365, 2011
KEYWORDS: conjugated polymers; copolymerization; light-emit-
ting diodes (LED); polyfluorene
INTRODUCTION In this tough era facing energy crisis, light-
emitting diode (LED) has become a new solution for the
next-generation solid-state lighting; the lower turn-on volt-
age and the higher power efficiency bring LED more compet-
itive advantage than the incandescent light bulb. Within the
LED technologies, white organic LEDs (WOLEDs) and poly-
mer LEDs (WPLEDs) have drawn many researchers’ interests
in the past decade because of their potential applications not
only in the solid-state lighting but also in full-color flat-panel
and liquid-crystal displays’ backlight.1–3 Despite the high
power efficiency of small-molecule WOLEDs, WPLEDs have
better advantage for the fabrication of large-area display
devices using inexpensive solution processing techniques
(e.g., spin-coating and printing technology).4–6 Various
approaches have been proposed to fabricate white polymeric
light-emitting devices; one is to obtain from multilayer de-
vice in which each layer emits partial segment of the visible
spectrum.7,8 Another conventional approach is to use poly-
mer-blend systems containing two or three light-emitting
materials as emissive layers, such as polymer/polymer
blends9–14 or polymer/small-molecule blends.15–20 Although
WPLEDs can be realized in these two ways, they still face
some problems. The first approach could meet some proc-
essing challenges, such as thin-film layer adjustment and sol-
vent selection, and the second strategy may suffer from
intrinsic phase separation during long-term device operation
as well as spectroscopic dependence on the applied voltage.
Recently, studies have developed single-component white
polymeric emitter based on insufficient energy transfer by
incorporating RGB chromophores into a single polymer
chain.21–31 This promising method could go through a simple
solution process thus make the device fabrication easier. Lee
et al. first reported a single fluorene-based copolymer com-
posed of blue-, green-, and red-light emitting units as active
material for WPLED, which showed a maximum brightness
of 820 cd/m2 at 11V with the Commission Internationale de
l’Eclairage (CIE) coordinates of (0.33, 0.35).23 At almost the
same time, Wang and coworkers adopted a slightly different
synthetic strategy by which green- and red-emitting compo-
nents were attached to the pendant chain along with blue-
emitting polyfluorene backbone.28,29 Cao and coworkers syn-
thesized a conjugated silole-containing polyfluorenes, with
green- and red-emissive siloles on the blue-emissive poly-
fluorene backbone. The electroluminescence (EL) device
showed a maximum brightness and luminous efficiency of
4102 cd/m2 and 2.03 cd/A, respectively.31
Although using single white emitting polymers as emitting
layer provides an easier way for device fabrication, more
efforts should be done in their synthetic strategies. The gen-
eral synthetic routes for preparing polyfluorenes are organo-
metallic cross-coupling reactions, such as Suzuki coupling or
Yamamoto coupling. As a result, however, it is unlikely to
remove the metal-catalyst completely from the resultant
Correspondence to: C.-S. Hsu (E-mail: cshsu@mail.edu.tw)
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Journal of Polymer Science Part A: Polymer Chemistry, Vol. 49, 3355–3365 (2011) 2011 Wiley Periodicals, Inc.
WHITE-LIGHT SINGLE POLYFLUORENES, LO AND HSU
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
polymers during purification. The azide-alkyne click reaction
is a new way to prepare polyfluorenes in mild conditions.32–38
Tang and coworkers developed a metal-free, thermally initi-
ated, regioselective 1,3-dipolar polycycloaddition process:
simple heating a mixture of arylenediazides (N3AArAN3) and
arylenediynes (HAC:C-Ar-C:CAH) in a polar solvent, such
as N,N-dimethylforamide (DMF)/toluene mixture, readily fur-
nished a linear poly(1,2,3-triazole) with a high regioregularity
(1,4-disubstitued content ratio up to ꢁ92%) in a high yield
(up to ꢁ98%).38
In this article, we report two series of polymers: the first con-
tained four fluorene-based polymers with specific end-cap-
ping groups (PFs: PFB1, PFB2, PFG1, and PFR1) synthesized
via Suzuki polycondensations, and another series involved
single-chain white-light polymers (WPFs), which linked via
1,2,3-triazole-ring, obtained by incorporating a small amount
of PFG1 and PFR1 into PFB’s backbone through azide-alkyne
click reaction. The EL spectra of these novel WPFs showed
three distinguishable emissions peaks at blue, green, and red
area due to the incomplete energy transfer from the blue-
emissive (PFB1 and PFB2) to the green- (PFG1) and red-emis-
sive (PFR1). The relative intensities of these three emissions
vary in accordance with the relative composition proportion
of the four basic PFs. Furthermore, the molecule weight, ther-
mal stability, EL properties (brightness, efficiency, and CIE),
and other relevant physical properties of the synthesized
polymers were also investigated.
Fabrication and Characterization of PLED Devices
The multilayers PLED devices were fabricated as sandwich
structures between cathode (Cs) and indium-tin oxide (ITO)
anodes in the following configuration: ITO/poly(styrenesulfo-
nate)-doped poly(3,4-ethylenedioxythiophene)(PEDOT:PSS)/
TFB(hole-transporting material, which is poly[(9,9-dioctyl-
fluorenyl-2,7-diyl)-co-(4,40-(N-(4-s-butylphenyl))diphenylami-
ne)])/light-emitting polymer/Cs/Al. ITO-coated glass sub-
strates were cleaned sequentially in ultrasonic baths of
detergent, 2-propanol/deionized water (1:1, v/v) mixture, tolu-
ene, deionized water, and acetone. A 50-nm thick hole injection
layer of PEDOT:PSS was spin-coated on the top of ITO at 3000
rpm for 40 s and then dried at 150 ꢀC for 1 h under N2. TFB was
dissolved in toluene of 1.0 wt % and spin-coated at 2000 rpm
for 30 s as hole-transporting layer and then dried at 80 ꢀC for 1
h under N2. The following construction of the emitting layer
may destroy the flatness of the interface between hole-trans-
porting and emitting films due to the TFB, and our active mate-
rials are both organic soluble. The method to overcome this
shortcoming is the buffer layer technology by using water-solu-
ble ethylene glycol as buffer solvent between two organic-solu-
ble layers. The detailed procedure of buffer layer technology
was showed as the following steps: first, the program of spin
coater was set for three steps of 5000 rpm for 3 s, 0 rpm for 3.5
s, and 1500 rpm for 30 s in sequence. Second, the program of
spin coater started immediately after the ethylene glycol of 60
lL was dropped from their 1.5 wt % toluene solutions on the
PEDOT layer, and then WPFs of 1.5 wt % in toluene were
dropped rapidly during the 3.5 s of the spinner was suspended.
After the program was finished, the films of WPFs were dried at
EXPERIMENTAL
ꢀ
100 C under vacuum for 2 h. The film thicknesses obtained
Measurements
were about 40ꢁ50 nm, which were measured by an Alpha-Step
500 surface profiler (KLA Tencor, Mountain View, CA). Finally,
2-nm Cs and 100-nm Al electrodes were thermally evaporated
through a shadow mask onto the polymer films using an AUTO
306 vacuum coater (BOC Edwards, Wilmington, MA), typical
evaporations being carried out at base pressures lower than 2
ꢃ 10ꢂ6 Torr. The active area of each EL device was character-
ized following a published protocol.
IR spectra were recorded on a Perkin-Elmer 16PC FTIR spec-
trometer with KBr pellets. The chemical structure is con-
firmed using 1H NMR spectra (300 MHz) on a Varian VXR-
300 spectrometer. Differential scanning calorimetry (DSC)
was recorded on a Perkin-Elmer Pyris Diamond DSC uꢂn1it
ꢀ
operated at heating and cooling rates of 20 and 50 C min
,
respectively. Samples were scanned from 30 to 300 ꢀC,
cooled to 0 ꢀC, and then scanned a second time form 30 to
300 ꢀC. The glass transition temperatures were determined
from the second heating scans. Thermogravimetric analyses
(TGA) were undertaken on a Perkin-Elmer Pyris 1 TGA
instrument to determine the stabilities of samples by meas-
Materials
All chemicals, reagents, and solvents were used as received
from commercial sources without further purification except
tetrahydrofuran (THF) and toluene that have been distilled
over sodium/benzophenone. The Suzuki coupling catalyst re-
agent tetrakis(triphenylphosphine)palladium (0) were pur-
chased from TCI and handled under inert atmosphere.
ꢂ1
ꢀ
uring their weight losses with a heating rate of 10 C min
.
UV–visible spectra were measured with an HP 8453 diode
array spectrophotometer. PL spectra were obtained on a
Hitachi F-4500 luminescence spectrometer, and the PL exter-
nal efficiency was measured using an integrating sphere.
Cyclic voltammetry measurements of the material were done
in acetonitrile with 0.1 M tetrabutylammonium hexafluoro-
phosphate (TBAPF6) as the supporting electrolyte at a scan
rate of 80 mV/s. Platinum wire electrodes were used as both
the counter and working electrodes, and silver/silver ion
(Ag/Agþ in 0.1 M AgNO3 solution, from Bioanalytical Sys-
tems) was used as a reference electrode. Using ferrocene as
an internal standard, the potential values obtained were con-
verted to vs SCE (saturated calomel electrode).
Monomers, 2,7-dibromo-9,9-di-n-hexylfluorene (M1),39 2,7-
bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9-dihexylfluor-
ene (M2),40 4,7-bisbromo-2,1,3-benzo-thiadiazole (M4),39
N,N-di(4-bromophenyl)-N-(4-butylphenyl)amine (M3), and
4,7-bis-(5-bromo-2-thienyl)-2,1,3-benzothiadiazole
were synthesized according to literature procedures.
(M5),41
4-(4-Bromophenyl)-2-methylbut-3-yn-2-ol (4)
A solution of 4-bromo-iodobenzene (10.0 g, 35.35 mmol),
trans-dichloro-bis(triphenyl-phosphine)palladium(II) (0.5 g,
0.71 mmol), and triphenylphosphine (1.87 g, 7.10 mmol) in
3356
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ARTICLE
triethylamine (150 mL) was stirred at 60 ꢀC for 30 min
under N2. Then copper(I) iodide (1.0 g, 5.26 mmol) and 2-
methylbut-3-yn-2-ol (4.36 g, 53.02 mmol) were added into
the flask. The mixture was heated to reflux for 16 h under
N2. After cooling, the solution was extracted with ethyl ace-
tate, and the organic phase was dried over magnesium sul-
fate, filtered, rotary evaporated to remove solvent. The crude
product was purified by column chromatography using ethyl
acetate/n-hexane (1:5, v/v) as eluent to yield 4 as a brown
solid (5.91 g, 70.2 %).
4-Bromophenyl Azide (M8)
4-Bromoaniline (10.0 g, 58.13 mmol) and 50 mL THF were
added into a three-necked flask. Concentrated hydrochloric
ꢀ
acid (10.3 mL, 87.2 mmol) was added carefully at 0 C. A so-
lution of sodium nitrite (6.07 g, 87.2 mmol) in 15-mL THF
was added drop-wise within 30 min. Then sodium azide (5.8
g, 87.2 mmol) dissolved in 15-mL THF was added drop-wiꢀse
within 30 min. Afterward, the mixture was refluxed at 85 C
for 24 h. After the mixture was cooled to room temperature,
THF was removed by rotary evaporation, and then the mix-
ture was mixed with 100 mL of water and extracted with
100 mL ethyl acetate. The extracted solution was dried over
anhydrous magnesium sulfate. The crude product was iso-
lated by filtration and further purified by column chromatog-
raphy (silica gel, eluting with n-hexane) to yield M8 as
brown liquid (5.23 g, 45.5%).
1H NMR (300 MHz, CDCl3, d in ppm): 1.61 (s, 6H, ACH3),
2.01 (s, 1H, AOH), 7.26ꢁ7.28 (d, 2H, aromatic protons),
7.42ꢁ7.45 (d, 2H, aromatic protons). 13C NMR (75 MHz,
CDCl3, d in ppm): 32.1 (2C, ACH3), 65.3 (1C, AC(CH3)2OH),
80.3 (1C, Ar-C:C), 93.4 (1C, Ar-C:C), 121.7, 122.8, 131.3,
134.5 (aromatic carbons). HRMS-EI (m/z): [Mþ] calcd. for
C11H11BrO, 237.9993; found, 237.9912.
1H NMR (300 MHz, CDCl3, d in ppm): 6.88ꢁ6.91 (d, 2H, aro-
matic protons), 7.44ꢁ7.47 (d, 2H, aromatic protons). 13C
NMR (75 MHz, CDCl3, d in ppm): 123.1, 131.0, 131.7, 143.5
(aromatic carbons). HRMS-EI (m/z): [Mþ] calcd. for
C6H4BrN3, 196.9589; found, 196.9572.
1-Bromo-4-ethynylbenzene (M6)
4-(4-Bromophenyl)-2-methylbut-3-yn-2-ol (4) (8.0 g, 33.46
mmol) and potassium hydroxide (5.63 g, 100.38 mmol) were
mixed in 150 mL 1,4-dioxane. The mixture was stirred at
120 ꢀC for 3 h. The reactant was cooled to room tempera-
ture, and then the solvent was stripped off by evaporation.
The residue was mixed with 80 mL of water and extracted
with 80 mL ethyl acetate. The extracted solution was dried
over anhydrous magnesium sulfate. The crude product was
purified by column chromatography (silica gel, eluting with
hexane) to yield M6 as deep brown liquid (5.18 g, 85.5%).
4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolane-2-yl)aniline (5)
To a solution of 4-bromoanniline (10.0 g, 58.13 mmol) in
THF (50 mL) at ꢂ78 ꢀC n-butyllithium (30.22 mL, 2.5 M in
hexane, 75.57 mmol) was added by syringe. The mixture
was stirred at ꢂ78 ꢀC for 1 h. 2-Isopropoxy-4,4,5,5-tetra-
methyl-1,3,2-dioxaborolane (15.39 mL, 75.57 mmol) was
added rapidly to the solution, and the resulting mixture was
warmed to room temperature and stirred for 24 h. The mix-
ture was poured into water and extracted with ethyl acetate.
The solvent was removed by rotary evaporation, and the res-
idue was purified by column chromatography (silica gel,
eluting with ethyl acetate/n-hexane, 1:5, v/v) to yield 5 as
yellow liquid (5.37 g, 42.2 %).
1H NMR (300 MHz, CDCl3, d in ppm): 3.10 (s, 1H, acetylene
proton), 7.31ꢁ7.34 (d, 2H, aromatic protons), 7.42ꢁ7.45(d,
2H, aromatic protons). 13C NMR (75 MHz, CDCl3, d in ppm):
82.4 (1C, Ar-C:C), 79.9 (1C, Ar-C:C), 121.1, 122.1, 130.5,
134.3 (aromatic carbons). HRMS-EI (m/z): [Mþ] calcd. for
C8H5Br, 179.9575; found, 179.9523.
1H NMR (300 MHz, CDCl3, d in ppm): 1.25 (s, 12H, ACH3),
3.62 (s,1H, ANH2), 6.54ꢁ6.57 (d, 2H, aromatic protons),
7.21ꢁ7.24 (d, 2H, aromatic protons). 13C NMR (75 MHz,
CDCl3, d in ppm): 20.8 (4C, ACH3), 82.7 (2C, -boronic ester
ring carbons), 116.3, 122.0, 134.7, 148.4 (aromatic carbons).
HRMS-EI (m/z): [Mþ] calcd. for C12H18BNO2, 219.1431;
found, 219.1423.
2-[4-(1-Ethynyl)phenyl]-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (M7)
To a solution of 2-[4-(1-ethynyl)phenyl]-4,4,5,5-tetramethyl-
1,3,2-dioxa-borolane (M6; 3.0g, 16.57 mmol) in THF (30 mL)
was added n-butyllithium (8.62 mL, 2.5 M in hexane,
ꢀ
21.55mmol) by syringe under ꢂ78 C. The mixture was then
stirred at ꢂ78 ꢀC for 1 h. 2-Isopropoxy-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (4.39 mL, 21.55 mmol) was added rapidly
to the solution, and the resulting mixture was warmed to room
temperature and stirred for 24 h. The mixture was poured into
water and extracted with ethyl acetate. The solvent was then
removed by rotary evaporation, and the residue was purified
through column chromatography (silica gel, eluting with n-hex-
ane) to yield M7 as deep brown liquid (2.50 g, 66.2%).
4(4,4,5,5-Tetramethyl-1,3,2-dioxaborolane-2-yl)phenyl
azide) (M9)
4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolane-2-yl) aniline (5)
(3.0 g, 13.69 mmol) and 20-mL THF were added into a
three-necked flask. Concentrated hydrochloric acid (2.42 mL,
20.53 mmol) was added carefully at 0 ꢀC. Sodium nitrite
(1.42 g, 20.53 mmol) dissolved in 8 mL THF was added
drop-wise within 30 min. Then a solution of sodium azide
(1.36 g, 20.53 mmol) in 8 mL THF was added drop-wise
within 30 min. Afterward, the mixture was heated to reflux
for 24 h. After the mixture was cooled to room temperature,
THF was removed by rotary evaporation, and the mixture
was mixed with 50 mL of water and extracted with 50 mL
ethyl acetate. The extracted solution was then dried over an-
hydrous magnesium sulfate. The crude product was filtrated
1H NMR (300 MHz, CDCl3, d in ppm): 1.25 (s, 12H, ACH3),
3.10 (s, 1H, acetylene proton), 7.31ꢁ7.34 (d, 2H, aromatic
protons), 7.42ꢁ7.45 (d, 2H, aromatic protons). 13C NMR (75
MHz, CDCl3, d in ppm): 21.4 (4C, ACH3), 83.2 (2C, -boronic
ester ring carbons), 82.1 (1C, Ar-C:C), 79.7 (1C, Ar-C:C),
121.7, 122.7, 132.3, 133.5 (aromatic carbons). HRMS-EI (m/
z): [Mþ] calcd. for C14H17BO2, 228.1322; found, 228.1352.
WHITE-LIGHT SINGLE POLYFLUORENES, LO AND HSU
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
TABLE 1 The Mole Feed Ratios of Basic PFs for Single-
and further purified by column chromatography (silica gel,
eluting with n-hexane) to yield M9 as yellow liquid (1.30 g,
38.6%).
Polymers WPFs
PFB2
PFB1
PFG1
PFR1
1H NMR (300 MHz, CDCl3, d in ppm): 1.25 (s, 12H, ACH3),
7.28 (s, 4H, aromatic protons). 13C NMR (75 MHz, CDCl3, d
in ppm): 21.2 (4C, ACH3), 83.1 (2C, -boronic ester ring car-
bons), 128.8, 132.0, 133.9, 144.5 (aromatic carbons). HRMS-
EI (m/z): [Mþ] calcd. for C12H16BN3O2, 245.1336; found,
245.1321.
WPF1
WPF2
WPF3
WPF4
WPF5
WPF6
0.5
0.5
0.5
0.5
0.5
0.5
0.3
0.1
0.1
0.3
0.06
0.05
0.04
0.05
0.02
0.14
0.1
0.35
0.38
0.40
0.42
0.08
0.05
0.06
Synthesis of Fluorene-Based Conjugated Polymers (PFs)
A typical procedure for the polymerization of PFB2 was
given below. Into a three-necked flask were added 2,7-
bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9-dihexylfluor-
ene (M2; 0.5 g, 0.85 mmol), 2,7-dibromo-9,9-di-n-hexylfluor-
ene (M1) (0.25 g, 0.43 mmol), N,N-di(4-bromophenyl)-N-(4-
butylphenyl)amine (M3; 0.19 g, 0.43 mmol), Pd(PPh3)4
(0.015 g, 0.01 mmol), and Aliquat 336 (a small amount) in a
dry box. Degassed toluene (7 mL) and aqueous K2CO3 (2 M,
3 mL) were then added, by syringe, under an atmosphere of
dry argon. The mixture was heated to reflux with vigorous
stirring at 90 ꢀC oil bath for 96 h. The end groups were
capped by heating the mixture under reflux for 12 h with M8
(0.07 g, 0.35 mmol) and then with M9 (0.08 g, 0.35 mmol)
for another 12 h. The reaction mixture was cooled to room
temperature and poured into methanol. The precipitation was
collected by filtration and washed by acetone to remove
oligomers and catalyst residues. The precipitation was then
redissolved in THF, reprecipitated in methanol, and finally
dried with vacuum oven at 35 ꢀC to give PFB2. PFB1, PFG1,
and PFR1 were also synthesized through the above proce-
dure, except the different end-capping reagents (M6 and M7)
were used. The yields of these four polymers were in the
range of 66ꢁ75%.
synthesized via Suzuki polycondensations from monomers
M1ꢁM5, and another is novel copolymers with 1,2,3-tria-
zole-ring linkage, which were synthesized via azide-alkyne
click reaction from aforementioned PFs to afford WPFs.
Scheme 1 shows the general synthetic routes toward mono-
mers M1ꢁM9, and the chemical structures of all the mono-
mers were carefully checked with 1H NMR, 13C NMR, and
GC-MS results. Scheme 2 demonstrates the syntheses of the
four basic PFs (PFB1, PFG1, PFR1, and PFB2), utilizing palla-
dium-catalyzed Suzuki coupling reaction with an equivalent
molar ratio of the diboronic ester monomer (M2) to the
dibromo monomers (M1, M3ꢁM5) under argon atmosphere.
Monomers (M6 and M7 with arylacetylene end group; M8
and M9 with arylazide end group) were used as the end-cap-
ping reagents for Suzuki coupling polymerization.
A new series of WPF polymers were synthesized via an acet-
ylene-azide click reaction by using the specific end-capped
polymers as reactants (PFB1 and PFB2 act as host units
while PFG1 and PGR1 act as dopants). The chemical struc-
tures of these novel WPFs, which were composed of the four
PFs in different ratios, are showed in Scheme 3. The mole
feed ratios used in the preparation of the WPFs were listed
Synthesis of Single-Chain WPF Copolymers
1
To diminish the difficulty during purification, we adopted a
metal-free, thermally initiated process. With four basic PFs
(PFB1, PFG1, and PFR1 with arylenediyne end-capped
groups; PFB2 with arylenediazide end-capped group) in
hand, a series of novel single WPFs with 1,2,3-triazole-ring
linkage were obtained through azide-alkyne click reaction.
The mole feed ratios used in the preparation of these new
polymers were given in Table 1. A typical procedure for the
synthesis of WPF WPF5 was given below. To a solution of
PFB2 (0.1 g), PFB1 (0.08 g), PFG1 (0.01 g), and PFR1 (0.01
g) in DMF/toluene (1:1, v/v; 10 mL) was heated to reflux
with vigorous stirring under 110 ꢀC oil bath for 72 h at an
atmosphere of dry argon. The reaction mixture was then
cooled to room temperature and poured into methanol. The
precipitation was collected by filtration and dried with vac-
uum oven at 35 ꢀC to give WPF5. The yields of these four
single polymers were in the range of 55ꢁ70%.
in Table 1. The resulting polymers were characterized by H
NMR and FTIR to confirm the polymer structures and to ver-
ify the completion of click-reaction. Figure 1 shows the FTIR
spectra of polymers PFB1, PFB2, and WPF5; PFB1 absorbs
at 3236 and 2102 cmꢂ1 due to its :CAH and C:C stretch-
ing vibrations, respectively. PFB2 exhibits a strong absorp-
tion peak at 2030 cmꢂ1 associated with the stretching of its
azide group. For the FTIR spectrum of WPF5, all these three
absorption peaks disappeared. This suggests that all the
acetylene and azide groups of PFs have been transformed to
the triazole rings of the polymers WPFs through the click
reaction. Although the FTIR spectra support that the click
reaction is feasible to obtain a triazole-linked polymer, they
offer no information about the regioselectivity (1,4- or 1,5-
disubstitution) of the polymers. We used the NMR technique
to study this important structural issue. Figure 2 shows the
NMR spectra of polymers PFB1, PFB2, and WPF5. The 1H
NMR spectrum of polymer PFB2 exhibited no distinctive
peak for azide group. The resonance peak for the acetylene
proton of polymer PFB1 was found at d3.06. In the spectrum
of polymer WPF1, the peak for acetylene group at d3.06
became remarkable weaker, and furthermore, a new peak
RESULTS AND DISCUSSION
Synthesis and Characterization
We synthesized two series of polymers successfully; the first
is fluorene-based conjugated polymers (PFs), which were
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SCHEME 1 Synthetic routes of
monomers M1ꢁM9.
corresponding to the resonances of triazole ring protons
appeared at d9.03, which was the characteristic peaks for
1,4-disubstituted 1,2,3-triazole rings. The data of 1H NMR
spectra not only confirmed that the click reaction was
achievable but also determined the regioselectivity of the
polymer products.
Molecular weights and polydispersity indices of all the poly-
mers were determined by GPC analysis using THF as the elu-
ent and polystyrene as the standard. The number–average
molecular weights (Mn), weight-average molecular weights
(Mw), and the polydispersity indices (PDIs) are summarized
in Table 2. The range of the Mn and Mw for PFs were
WHITE-LIGHT SINGLE POLYFLUORENES, LO AND HSU
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
SCHEME 2 Polymerization of
polymers PFs.
determined to be 15,500–24,300 and 24,200–38,200, respec-
tively, with the PDI range of 1.52–1.70. The Mn and Mw of
all the WPFs were both about four to six times than that of
PFs. The higher molecular weights of WPFs compared with
PFs suggest successful combination of four basic PFs result-
ing the novel triazole-linked WPFs. All the polymers are
readily soluble in common organic solvents, such as toluene,
chlorobenzene, chloroform, and THF at room temperature.
Accordingly, uniform thin films of the polymers could easily
produced through spin-coating for further study of light-
emitting devices.
As good thermal stability is very important for the applica-
tion of conjugated polymers in flat panel displays, the ther-
mal stability of these polymers was evaluated by TGA and
DSC under a nitrogen atmosphere. Table 2 summarizes the
glass transition temperatures (Tg) and thermal decomposi-
tion temperatures (Td) of the obtained polymers. Both PFs
and WPFs exhibit outstanding thermal stability, with the
decomposition temperatures (Td) higher than 385 ꢀC, and
their glass transition temperatures are in the range from 80
ꢀ
to 110 C, which are similar with those of polyfluorene pub-
lished in the literature.23
SCHEME 3 Syntheses of WPFs by click reaction.
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ARTICLE
that of 429 nm to lead to polymer WPF1 emits orange-red
light. As shown in Figure 5, the relative intensities of long
wavelength peaks decreased gradually for WPF2ꢁWPF6 by
decreasing the contents of PFG1 and PFR1. White-light single
polymers (WPF3ꢁWPF5) were obtained from polymers con-
taining 85ꢁ90 mol % blue-light emitting host and 10ꢁ15
mol % green- and red-light emitting dopant. The data of UV–
vis and PL spectra were listed in Table 3.
FIGURE 1 FTIR spectra of PFB1, PFB2, and WPF5.
Optical Properties
The fluorescent wavelength of a polymer film fundamentally
depends on the band gap between the highest occupied mo-
lecular orbital (HOMO) and lowest unoccupied molecular or-
bital (LUMO), which depends on delocalization of p electrons
along the polymer backbone. The characteristic peak in the
emission spectrum appears when an excited electron relaxes
into vibronic energy level of the HOMO level. Because of the
coupling of several different vibronic modes, the optical spec-
tra of conjugated polymers are typically broad. UV–vis absorp-
tion and photoluminescence spectra of the four PFs polymer
in dilute toluene solution and thin film state were showed in
Figures 3 and 4, respectively. The polymers PFB1 and PFB2
exhibit similar UV–vis and photoluminescence spectra
because of their similar chemical structures (the only discrep-
ancy is in end-capping reagents); they both emitted blue emis-
sions with photoluminescence maxima of about 416 and 428
nm in dilute toluene solution and solid state, respectively. By
introducing a small amount of BTDZ group into the main
chain of polyfluorene copolymer, the blue emission at 428 nm
of polyfluorene could be quenched and dominated by a green-
and red-emissive peaked at 532 and 617 nm for PFG1 and
PFR1, respectively. This indicates the effectively energy trans-
fer from photogenerated excitons on the polyfluorene seg-
ment into BTDZ groups, and the more planar backbone and
the smaller band gap were produced. The maximum wave-
lengths of UV–vis absorption and PL emission for these four
polymers in diluted toluene solution and solid state were
summarized in Table 3. In comparison with dilute solution,
the absorption and emission spectra of PFs in thin film state
both showed slightly red-shift, and this phenomenon can be
attributed to the aggregation of polymer chains.
Figure 5 shows the photoluminescence spectra of WPFs in
thin film state. It can be seen that the absorption spectra of
these polymers are practically identical to that of the poly-
mer PFB1 because of the very low contents of polymers
PFG1 and PFR1. In the PL spectra of these polymers (Fig. 5),
WPF1 exhibits two obvious emission peaks at 429 nm and
558 nm, and the intensity of 558 nm is much stronger than
FIGURE 2 1H NMR spectra of (a) PFB1, (b) PFB2, and (c) WPF5.
[Color figure can be viewed in the online issue, which is avail-
able at wileyonlinelibrary.com.]
WHITE-LIGHT SINGLE POLYFLUORENES, LO AND HSU
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
TABLE 2 Average Molecular Weights and Thermal Properties
TABLE 3 UV and PL Peaks of Polymers PFs
PL [kmax (nm)]
of Polymers PFs and WPFs
PLeff (%)a
Mna
(ꢃ 104)
Mwa
(ꢃ 104)
PDI
polymer Toluene Film
Toluene Film Toluene Film
Polymer
(Mw/Mn)
Td (ꢀC)
Tg (ꢀC)
PFB2
PFB1
PFG1
PFR1
380
383
388
381
384
388
416
419
428 82.2
427 80.7
55.3
50.7
42.8
37.1
PFB2
PFB1
PFG1
PFR1
WPF1
WPF2
WPF3
WPF4
WPF5
WPF6
a
2.4
1.7
3.8
2.6
1.61
1.55
1.70
1.52
1.88
1.93
1.90
1.99
2.02
1.78
412
406
398
403
393
385
401
409
411
415
82.2
81.3
380(455) 422,529 532 86.6
382 429,609 617 70.7
1.5
2.5
92.5
1.6
2.4
95.8
(455,525) (458,530)
8.40
8.39
8.73
8.79
9.20
10.56
15.8
16.2
16.6
17.5
18.6
18.8
108.1
103.9
99.2
a
The PL external efficiency was measured using an integrating sphere.
101.9
96.6
93.0
Determined by GPC, relative to polystyrene standards.
FIGURE 5 Photoluminescence spectra of white-light polymers
WPFs in film state. [Color figure can be viewed in the online
issue, which is available at wileyonlinelibrary.com.]
Electrochemical Properties
The electrochemical behavior of these polymers was investi-
gated by cyclic voltammetry (CV). The corresponding HOMO
energy levels were estimated from the oxidation onset
potentials. HOMO levels of all the polymers were calculated
according to the empirical formula EHOMO ¼ ꢂ(Eox þ 4.4)
(eV). Polymers coated on a Pt wire from toluene solution
were performed in an electrochemical cell with a Pt counter
electrode and an Hg reference electrode. From the difference
of the onset potentials and the band gaps (Eg) calculated
from the onsets of UV absorption spectra, the energy levels
FIGURE 3 UV–vis spectra of polymers PFs in dilute toluene and
film state.
TABLE 4 Energy Levels of Polymers PFs
Energy Level (eV)
Eox,onset (V)a
HOMOb
LUMOb
Eg
c
PFB2
PFB1
PFG1
PFR1
a
1.25
1.23
1.41
1.37
5.65
5.63
5.81
5.77
2.71
2.69
3.16
3.62
2.94
2.94
2.65
2.15
The Eox stands for the onset potentials of oxidation.
b
Calculated from the empirical formula, E(HOMO) ¼ ꢂ(Eox þ 4.40) (eV),
FIGURE 4 Photoluminescence spectra of polymers PFs in dilute
toluene and film state. [Color figure can be viewed in the
online issue, which is available at wileyonlinelibrary.com.]
E(LUMO) ¼ ꢂ(Ered þ 4.40) (eV).
c
The energy gap (Eg) was estimated from the onset wavelength (value
in parentheses) of UV–vis spectra of the polymer film.
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ARTICLE
FIGURE 7 Electroluminescence spectra of white-light polymers
WPFs at 8 V. [Color figure can be viewed in the online issue,
which is available at wileyonlinelibrary.com.]
FIGURE 6 Electroluminescence spectra of polymers PFs. [Color
figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
were determined and displayed in Table 4. It can be seen
that polymers PFB1 and PFB2 possess the similar electro-
chemical properties to homo-polyfluorene. The reversible ox-
idation curve of PFB1 and PFB2 with onset at 1.23 and 1.25
V, respectively (in agreement with data reported previously
for polyfluorene homopolymer) that could be assigned to the
oxidation potential of polyfluorene main chains and indicated
that the end-capping group made no effect to electrochemi-
cal properties of polymers PFs. When compared with poly-
fluorene homopolymer (Eg of PFO were 2.95 eV), the Eg of
polymers PFG1 and PFR1 show a less value because the
incorporation of the electron-rich BTDZ moiety.39 As BTDZ
moiety has a smaller band gap than polyfluorene, the excita-
tion energy on the fluorene segments can transfer to the
BTDZ units with high efficient green and red lights. The dif-
ference in chemical structure between the WPFs and the ba-
sic polymers (PFs) is the particular triazol-ring. As the
results in Table 4, polymers WPFs all exhibited the very sim-
ilar electrochemical behavior with that of the basic polymers
PFs, indicating that the triazol-ring leads to little change in
the resulting polymers’ redox properties.
Electroluminescence
For evaluating the EL properties of these single WPFs, the devices
with a configuration of ITO/PEDOT:PSS (30 nm)/TFB (15 nm)/
light-emitting polymer (50ꢁ60 nm)/Cs (2 nm)/Al (100 nm)
were fabricated. Figures 6 and 7 show the EL spectra of PLED
devices with polymers PFs and WPFs as active layers, respec-
tively. PFBs, PFG1, and PFR1 exhibited blue (kmax ¼ 428), green
(kmax ¼ 528), and red (kmax ¼ 618) emissions, respectively.
WPFs all exhibited simultaneous blue, green, and red emissions
originating from the polyfluorene backbone, 2,1,3-benzothiadia-
zole unit, and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole unit,
respectively. The feed ratios of RGB PFs significant tuned the
color of WPFs devices, and the white emission was achieved by
fairly balance of RGB emissions. For EL spectra of polymers
WPF1ꢁ2, the intensity of green and red peaks was much stron-
ger than blue peak, leading to CIE coordinates in yellow light
region (see Table 5). This might be attributed to the higher con-
tents of green and red derivative units that introduced. Similarly,
polymer WPF6 with higher content of blue derivative unit exhib-
ited blue emission with CIE coordinates of (0.22, 0.22) presum-
ably. The EL spectra of WPF3ꢁ5 showed white emission with
TABLE 5 Device Performance of All the Polymers
Polymer
CIE(x,y)a
Vturn on (V)
Luminance (cd/m2)b
Yield (cd/A)b
Yield (cd/A)c
Yield (cd/A)d
PFB2
PFB1
PFG1
PFR1
WPF1
WPF2
WPF3
WPF4
WPF5
WPF6
a
(0.19,0.18)
(0.20,0.18)
(0.28,0.49)
(0.63,0.31)
(0.42,0.45)
(0.45,0.40)
(0.30,0.32)
(0.31,0.31)
(0.30,0.33)
(0.22,0.22)
5
5
6
5
5
5
5
5
5
5
3,955
4,341
10,186
2,383
3,644
3,483
6,697
7,174
7,551
6,412
c
1.62
1.83
5.62
1.16
5.24
3.06
3.66
5.47
6.21
4.16
1.21
1.27
2.92
0.59
1.10
1.54
1.93
2.11
1.73
2.14
0.86
1.66
4.6
0.95
4.15
2.02
3.37
4.79
5.46
3.83
CIE coordination at 8 V.
Yield with current density at 300 mA/cm2.
Yield with luminance at 100 cd/m2.
b
d
Maximum luminance and yield.
WHITE-LIGHT SINGLE POLYFLUORENES, LO AND HSU
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
FIGURE 8 Electroluminescence spectra of white-light polymers
WPF3 during bias scanning. [Color figure can be viewed in the
online issue, which is available at wileyonlinelibrary.com.]
FIGURE 10 Current efficiency-current density characteristics of
white-light polymers WPF3ꢁ5. [Color figure can be viewed in
the online issue, which is available at wileyonlinelibrary.com.]
1931 CIE coordinates close to that (0.33, 0.33) of standard white
emission [WPF3ꢁ5 at (0.30, 0.32), (0.31, 0.31) and (0.30, 0.33)
at 8 V, respectively]. It is noteworthy that these white-light devi-
ces displayed good color stability during the bias scanning. For
example, as showed in Figure 8, the EL spectrum of WPF3 almost
unchanged during the device operated from 6 to 10 V. As the
result of fine tune for the emissive color, we will pay much atten-
tion to WPFs WPF3ꢁ5 in the following discussions.
Table 5 summarizes the device performances of all the poly-
mers in the same fabricated condition. Figure 9 displays EL
performance of white-light emitting devices using polymers
WPF3ꢁ5 as emissive layer. A maximum brightness of 6697
cd/m2 (at 10 V) and a maximum yield of 3.66 cd/A were per-
formed from WPF3, while a maximum brightness of 7174 cd/
m2 (at 12.5 V) and a maximum yield of 5.47 cd/A were
achieved by WPF4. WPF5 showed the highest brightness of
7555 cd/m2 (at 13 V) and the maximum yield of 6.21 cd/A.
As the presentation in Figure 10, the luminous efficiency-cur-
rent density-brightness curves of these three white-light devi-
ces indicated the good stability of EL efficiency. For instance,
device WPF4 demonstrated the maximum EL efficiency of
4.79 cd/A with the brightness of 100 cd/m2 at the current
density of 2.5 mA/cm2. Moreover, its EL efficiency still held at
a good performance of 2.11 cd/A even with a high current
density of 300 mA/cm2 and brightness of 6335 cd/m2.
CONCLUSIONS
In this article, we have developed synthetic approaches to sin-
gle-chain WPFs with 1,2,3-triazole-ring linkage through azide-
alkyne cycloaddition (click reaction) using polyfluorene deriva-
tives with azide and alkyne end-capped groups as reactants.
The chemical structures of all the polymers were confirmed by
1H NMR and FTIR spectra, and the results of these measure-
ments also showed evidences to determine that the 1,2,3-tria-
zole-ring linkages were formed within the resulting single-
chain WPFs. The molecular weight of these novel polymers
(WPFs) were about four to six times (even up to 18.8 ꢃ 104)
than that of PFs due to the successful combination of four basic
PFs. Electroluminescent devices have been constructed with a
ITO/PEDOT/TFB/light-emitting polymer/Cs/Al configuration,
in which hole-transporting TFB were coated by buffer-layer
FIGURE 9 (a) Current density–voltage and (b) Luminance–volt-
age characteristics of white-light polymers WPF3ꢁ5. [Color fig-
ure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
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ARTICLE
21 Tsai, M. L.; Liu, C. Y.; Hsu, M.-A.; Chow, T. J. Appl Phys Lett
technology to achieve convenient and inexpensive solution pro-
cess for device fabrication. The devices fabricated from result-
ing polymers displayed white-light with blue, green and red
emissions simultaneously; moreover, the EL spectra of these
WPFs not only exhibited the CIE coordinates close to standard
white light (0.31, 0.31) but also showed color and EL stability
during the bias scanning. In all of our WPLED devices, the best
EL performance with a maximum brightness of 7551 cd/m2
and luminous efficiency as high as 6.21 cd/A was obtained on
the device using polymer WPF5 as emitting material.
2003, 82, 550–552.
22 Furuta, P.; Brooks, J.; Thompson, M. E.; Fre´chet, J. M. J. J
Am Chem Soc 2003, 125, 13165–13172.
23 Lee, S. K.; Hwang, D.-H.; Jung, B.-J.; Cho, N. S.; Lee, J.;
Lee, J.-D.; Shim, H.-K. Adv Funct Mater 2005, 15,
1647–1655.
24 Liu, J.; Zhou, Q. G.; Cheng, Y. X.; Geng, Y. H.; Wang, L. X.;
Ma, D. G.; Jing, X. B.; Wang, F. S. Adv Mater 2005, 17,
2974–2978.
REFERENCES AND NOTES
25 Tu, G. L.; Mei, C. Y.; Zhou, Q. G.; Cheng, Y. X.; Wang, L. X.;
Ma, D. G.; Jing, X. B.; Wang, F. S. Adv Funct Mater 2006, 16,
101–106.
1 Kido, J.; Kimura, M.; Nagai, K. Science 1995, 267, 1332–1334.
2 Tasch, S.; List, E. J. W.; Ekstro¨ m, O.; Graupner, W.; Leising,
26 Liu, J.; Zhou, Q. G.; Cheng, Y. X.; Geng, Y. H.; Wang, L. X.;
Ma, D. G.; Jing, X. B.; Wang, F. S. Adv Funct Mater 2006, 16,
957–965.
G.; Schlichting, P.; Rohr, U.; Geerts, Y.; Scherf, U.; Mullen, K.
¨
Appl Phys Lett 1997, 71, 2883–2885.
3 Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R.
N.; Mackay, K.; Friend, R. H.; Burns, P. L.; Holmes, A. B. Nature
1990, 347, 539–541.
27 Liu, J.; Xie, Z. Y.; Cheng, Y. X.; Geng, Y. H.; Wang, L. X.;
Jing, X. B.; Wang, F. S. Adv Mater 2007, 19, 531–535.
28 Liu, J.; Min, C. C.; Zhou, Q. G.; Cheng, Y. X.; Wang, L. X.;
Ma, D. G.; Jing, X. B.; Wang, F. S. Appl Phys Lett 2006, 88,
083505-1–083505-3.
4 Kraft, A.; Grimsdale, A. C.; Holmes A. B. Angew Chem Int Ed
1998, 37, 402–428.
5 Friend, R. H.; Gymer, R. W.; Holmes, A. B.; Burroughes, J. H.;
Marks, R. N.; Taliani, C.; Bradley, D. D. C.; Dos Santos, D. A.; Bredas,
J. L.; Logdlund, M.; Salaneck, W. R. Nature 1999, 397, 121–128.
29 Liu, J.; Tu, G. L.; Zhou, Q. G.; Cheng, Y. X.; Geng, Y. H.;
Wang, L. X.; Ma, D. G.; Jing, X. B.; Wang, F. S. J Mater Chem
2006, 16, 1431–1438.
6 Bernius, M. T.; Inbasekaran, M.; O’Brien, J.; Wu, W. Adv
30 Jiang, J. X.; Xu, Y. H.; Yang, W.; Guan, R.; Liu, Z. Q.; Zhen,
Mater 2000, 12, 1737–1750.
H, Y.; Cao, Y. Adv Mater 2006, 18, 1769–1773.
7 Zhou, Y.; Sun, Q. J.; Tan, Z. A.; Zhong, H. Z.; Yang, C. H.; Li,
31 Wang, F.; Wang, L.; Chen, J.; Cao, Y. Macromol Rapid Com-
Y. F. J Phys Chem C 2007, 111, 6862–6867.
mun 2007, 28, 2012–2018.
8 Xu, Y. H.; Peng, J. B.; Mo, Y. Q.; Hou, Q.; Cao, Y. Appl Phys
32 Liu, J.; Lam, J. W. Y.; Tang, B. Z. Chem Rev 2009, 109,
Lett 2005, 86, 163502-1–163502-3.
5799–5867.
9 Berggren, M.; Inganas, O.; Gustasson, G.; Rasmusson, J.; Ander-
¨
33 Qin, A.; Lam, J. W. Y.; Tang, B. Z. Chem Soc Rev 2010, 39,
sson, M. R.; Hjerberg, T.; Wennerstrom, O. Nature 1994, 372, 444–446.
2522–2544.
10 Ho, G. K.; Meng, H. F.; Lin, S. C.; Horng, S. F.; Hsu, C. S.;
34 Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B.
Chen, L. C.; Chang, S. M. Appl Phys Lett 2004, 85, 4576–4578.
Angew Chem Int Ed 2002, 41, 2596–2599.
11 Granstrom, M.; Inganas, O. Appl Phys Lett 1996, 68, 147–149.
¨
¨
35 Tornøe, C. W.; Christensen, C.; Meldal, M. J Org Chem
12 Shih, P.-I.; Tseng, Y.-H.; Wu, F.-I.; Dixit, A. K.; Shu, C.-F. Adv
2002, 67, 3057–3064.
Funct Mater 2006, 16, 1582–1589.
36 Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew Chem Int
13 Huang, J. S.; Li, G.; Wu, E.; Xu, Q. F.; Yang, Y. Adv Mater
Ed Engl 2001, 40, 2004–2021.
2006, 18, 114–117.
37 Qin, A.; Jim, C. K. W.; Lu, W. X.; Lam, J. W. Y.; Haussler,
¨
14 Zou, J. H.; Liu, J.; Wu, H. B.; Yang, W.; Peng, J. B.; Cao, Y.
M.; Dong, Y. Q.; Sung, H. H. Y.; Williams, I. D.; Wong, G. K. L.;
Tang, B. Z. Macromolecules 2007, 40, 2308–2317.
Org Electron 2009, 10, 843–848.
15 Kido, J.; Shionoya, H.; Nagai, K. Appl Phys Lett 1995, 67,
38 Qin, A.; Lam, J. W. Y.; Jim, C. K. W.; Zhang, L.; Yan, J. J.;
2281–2283.
Haussler, M.; Liu, J. Z.; Dong, Y. Q.; Liang, D.; Chen, E. Q.; Jia,
¨
16 Xu, Q. F.; Duong, H. M.; Wudl, F.; Yang, Y. Appl Phys Lett
G. C.; Tang, B. Z. Macromolecules 2008, 41, 3808–3822.
2004, 85, 3357–3359.
39 Ranger, M.; Rondeau, D.; Leclerc, M. Macromolecules 1997,
17 Kim, J. H.; Herguth, P.; Kang, M. S.; Jen, A. K.-Y.; Tseng, Y.
30, 7686–7691.
H.; Shu, C. F. Appl Phys Lett 2004, 85, 1116–1118.
40 Kreyenschmidt, M.; Klaerner, G.; Fuhrer, T.; Ashenhurst, J.;
Karg, S.; Chen, W. D.; Lee, V. Y.; Scott, J. C.; Miller, R. D. Mac-
romolecules 1998, 31, 1099–1103.
18 Kido, J.; Hongawa, K.; Okuyama, K.; Nagai, K. Appl Phys
Lett 1994, 64, 815–817.
19 Wu, H. B.; Zou, J. H.; Liu, F.; Wang, L.; Mikhailovsky, A.;
41 Treacher, K.; Becker, H.; Stossel, P.; Spreitzer, H.; Falcou,
A.; Parham, A.; Busing, A. (Merck Patent GmbH). German
Patent WO02-077060; U.S. Patent 7,288,617B2, March 22,
2002.
Bazan, G. C.; Yang, W.; Cao, Y. Adv Mater 2008, 20, 696–702.
20 Xu, Y. H.; Yang, R. Q.; Peng, J. B.; Mikhailovsky, A. A.; Cao,
Y.; Nguyen, T.-Q.; Bazan, G. C. Adv Mater 2009, 21, 584–588.
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