Pure blue-light-emitting materials: Hyperbranched ladder-type poly(p-phenylene)s containing truxene units

Article abstract of DOI:10.1021/ma9024448

A series of novel hyperbranched ladder-type poly(p-phenylene)s containing truxene units have been prepared through the Pd(0)-catalyzed Suzuki polymerization with an "A₂ + B₃" or "A ₂ + B₂+ B₃" approac

Full text of DOI:10.1021/ma9024448

Macromolecules 2010, 43, 731–738 731
DOI: 10.1021/ma9024448
Pure Blue-Light-Emitting Materials: Hyperbranched Ladder-Type
Poly( p-phenylene)s Containing Truxene Units
Yonggang Wu,*,† Xiaohui Hao,‡ Junling Wu,† Jia Jin,† and Xinwu Ba†,§
†College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China, ‡College of
Physics Science and Technology, Hebei University, Baoding 071002, China, and §Key Laboratory of Medical
Chemistry and Molecular Diagnosis, Ministry of Education, Baoding 071002, China
Received November 4, 2009; Revised Manuscript Received December 11, 2009
ABSTRACT: A series of novel hyperbranched ladder-type poly( p-phenylene)s containing truxene units
have been prepared through the Pd(0)-catalyzed Suzuki polymerization with an “A2 þ B3” or “A2 þ B2þ B3”
approach. The polymers with different linear length show pure blue light emission from 417 to 465 nm. All the
ladder-type polymers exhibit well-resolved absorption and emission spectra and small Stokes shifts in both
solutions and thin films, which are the characteristics of full ladder-type poly( p-phenylene)s. The three-
dimensional structures make the materials soluble in common organic solvents and able to form quality
amorphous films, leading to polymer light-emitting diodes (PLEDs) with improved stability and efficiency.
Introduction
of developing efficient light-emitting and other optoelectronic
devices.
Conjugated polymers have been extensively studied recently
due to their potential applications as light-emitting materials.1
For achieving full color displays, the three primary-color-emit-
ting materials, i.e., blue, green, and red, are essential. Compared
with the high brightness and efficiency of green- and red-light-
emitting materials, blue-light-emitting material does not match
requirements for commercially feasible light-emitting diodes.2
The search for stable light-emitting materials is ongoing. Poly-
fluorenes (PF),3 ladder-type poly(p-phenylenes) (LPPPs),4 are
generally regarded as the most promising blue-light emitters
because of their large band gap, well-defined structure, high
luminescence quantum yield, and color tenability. However, all
these materials suffer from the low-energy emission generated
during either annealing or passage of current in solid states.
Recent researches show the source of low-energy emission
attributed to aggregates/excimers or ketone defects in the poly-
mer molecular structure.5
Truxene and its derivatives are widely investigated as starting
materials for liquid crystals and fullerene precursors.10 Recently,
a variety of dendrimers and polymers containing truxene were
reported as light-emitting materials.11 The truxene moiety, as the
dendric units have unique three-dimensional topology, is easy to
functionalize at C-2, C-7, and C-12 positions and C-5, C-10, and
C-15 positions, respectively. Usually, six hexyl groups were
attached to the C-5, C-10, and C-15 positions of the truxene
moiety to increase solubility as well as to release intermolecular
π-π stacking. Truxene can be formally regarded as a derivative
of 1,3,5-triphenylbenzene with three -CH2- “clips” added and
accordingly three five-membered rings formed to keep the four
phenyls in a planar rigid structure, so the truxene moiety can be
introduced into the ladder-type poly(p-phenylene) as dentric
units to obtain hyperbrached structure.
In this paper, we report on the design, synthesis, and char-
acterization of a series of novel hyperbranched ladder-type
poly( p-phenylene)s containing truxene units (Figure 1). The
hyperbranched polymers containing different linear units show
the blue emission color from 417 to 465 nm. The keto-functio-
nalized precursor polymers HP1, HP2, and HP3 were prepared
by an “A2 þ B3” approach; the other polymer HP4 was obtained
by an “A2 þB2þ B3” approach. All the precursor polymers
quenched with 4-octyloxybenzene lithium were subsequently
The synthesis and the investigation of the photophysical
properties of ladder-type poly(p-phenylene)s (LPPP) were first
reported by Scherf and Mullen in 1991.4a The conjugated ladder-
€
type polymer possesses a rigid coplanar structure, which
enhances the conjugation, carrier mobility, and luminescence
intensity, whereas the rigid coplanar structuremore easily induces
the aggregation in molecular which produces the red-shifted or
excimers.6 To minimize this tendency for aggregation, several
attempts have been made such as introduction of bulky side
chains, copolymerization with suitable monomers, attachment of
sterically demanding end groups, or appending aryl groups onto
methylenes.7 The highly branched and globular features can
reduce or eliminate interchain interactions and π-π stacking
interactions between the planar-conjugated molecular chains.8
Moreover, three-dimensional structures make the materials
form good quality amorphous films so as to improve stability
and efficiency of PLEDs.9 Therefore, hyperbranched electro-
luminescent polymers have become of current interest in terms
treated with the BF3 ether to afford the hyperbranched ladder
3
polymers HLP(1-4) (HLP1, HLP2, HLP3, HLP4). The three-
dimensional polymers can be easily dissolved in common organic
solvents such as chloroform and THF to obtain good quality
amorphous films. All the polymers show good both thermal and
color stability, which establish them as good candidates for active
materials in stable pure blue polymer light-emitting diodes.
Results and Discussion
Synthesis and Characterization. The synthetic route to the
desired monomers and polymers is outlined in Scheme 1. To
prepare ladder-type poly( p-phenylene)s, it is necessary to
synthesize the key monomer MA1. Starting from the known
*Corresponding author: Fax þ86-312-5079317; e-mail wuyonggang@
hbu.edu.cn.
r 2009 American Chemical Society
Published on Web 12/29/2009
pubs.acs.org/Macromolecules

732 Macromolecules, Vol. 43, No. 2, 2010
Wu et al.
Figure 1. Structure of hyperbranched ladder-type polymers HLP(1-4).
reagent 1,4-dibromo-2,5-benzenedicarboxylic acid, mono-
mer MA1 was obtained via a two-step synthesis in a total
yield 76%. The reaction of excess MA1 with 1,4-benzenedi-
boronic acid pinacol ester afforded MA2 through Suzuki
coupling reaction in 30% yield. MA3 was obtained by
coupling excess MA1 and 2,7-bis(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)-9,9-dihexylfluorene (MB1) using Pd(0)-
(PPh3)4 as catalyst in 43% yield. 2,7,12-Triiodohexaethyl-
truxene was prepared via the route published by Pei et al.11f
MB2 was accomplished in a yield of 54% by the reaction of
2,7,12-triiodohexaethyltruxene and bis(pinacolato)diboron
in solution of DMF, CH3COONa, and Pd(dppf)2Cl2. The
nuclear magnetic resonance (NMR) spectroscopy, ele-
mental analysis, and matrix-assisted laser desorption/
ionization time-of-flight mass spectrometry (MALDI-
TOF MS).
Suzuki polycondensation (SPC) of the macromonomers
(A2: MA1, MA2, MA3) with B3: MB2 and B2: MB1 was done
in a biphasic system (THF/aqueous K2CO3) with freshly
prepared Pd(PPh3)4 as a catalyst precursor by the “A2 þ B3”
or “A2 þB2þ B3” approach. Reactions were kept stirring at
reflux for 72 h. 1-Bromo-4-methylbenzene was used to cap
the bronic end groups. Standard work-up afforded hyper-
branched polymers HP(1-4) (HP1, HP2, HP3, and HP4) as
amorphous solids in yields of 94%, 91%, 92%, and 96%,
1
high purity of the monomers was proved by H and 13C

Article
Macromolecules, Vol. 43, No. 2, 2010 733
Scheme 1. Synthesis of Monomers MA(1-3) and MB2
Scheme 2. Synthesis of Hyperbranched Ladder-Type Polymers HLP(1-4)
respectively. The keto groups of hyperbranched polymers
were quenched with largely excessive 4-octyloxybenzene
lithium to ensure all keto groups reduced completely
(Scheme 2). The final products HLP(1-4) were obtained
by the ring-closure reaction of the corresponding alcohol
polymers with boron trifluoride etherate via a intramolecu-
lar Friedel-Crafts alkylation in an overall yield 76%,
63%, 75%, and 58%, respectively. All polymers are easily
soluble in common organic solvents, such as THF, toluene,
chloroform, etc. The molecular structure of the polymers
was verified by H NMR spectroscopy and elemental ana-
1
lysis. The molecular weights of polymers HLP(1-4) were
determined by gel permeation chromatography (GPC) with
THF as the eluent, calibrated against polystyrene standards.
As shown in Table 1 and Figure 2, the GPC analysis indi-
cated that the number-average molecular weight (Mn) and
polydispersity index of the polymers are in the ranges
(2.2-23.0) ꢀ 104 and 1.5-4.7, respectively.

734 Macromolecules, Vol. 43, No. 2, 2010
Wu et al.
Table 1. Physical Properties of Hyperbranched Ladder-Type Poly-
mers HLP(1-4)
The thermal properties of the hyperbranchced ladder type
polymers HLP(1-4) were investigated by thermogravi-
metric analysis (TGA) and differential scanning calorimetry
(DSC) in a nitrogen atmosphere. All polymers exhibited
good thermal stability with onset degradation temperatures
(Td) above 330 °C (Figure 3). Neither a glass transition
process (Tg) nor other thermal processes (such as liquid-
crystal phase) were observed from 35 to 300 °C in the DSC
trace of second heating (10 °C/min).
polymers
Mn
Mw
PD
Td (°C)
HLP1
HLP2
HLP3
HLP4
35 100
21 500
24 100
233 000
136 300
101 500
69 300
3.89
4.71
2.87
1.75
359
347
341
335
407 400
Optical Properties. All polymers were readily dissolved in
common organic solvents such as methylene chloride, to-
luene, and THF and exhibited bright blue fluorescence in
solution. As shown in Figure 4 and Figure 5, the UV-vis
absorption and photoluminescence (PL) spectra of the pre-
cursor polymers HP(1-4) and the ladder-type polymers
HLP(1-4) in THF solution present an significant difference
which can be attributed to the change in the conformation.
HP(1-4) exhibited similar absorption and emission spectra
that were very broad and peaked at around 340 and 470 nm,
respectively, while the absorption peaks of ladder-type poly-
mers distinctly shifted toward low energy; on the contrary,
the emission peaks shifted toward high energy. The optical
properties of the ladder-type polymers were investigated in
both solution and solid state. The absorption and emission
spectra of HLP(1-4) in dilute THF solution are shown
in Figure 5. All the ladder-type polymers exhibited well-
resolved absorption and emission spectra, which is typical
for a rigid, planar, one-dimensional π-system. The absorp-
tion and emission maxima red-shifted with the increasing
linear length. The Stokes shifts of HLP(1-4) are 5, 4, 5, and 6
nm, respectively, indicating that such ladder-type polymers
are extremely rigid.
Figure 2. GPC elution traces of hyperbranched ladder-type polymers
HLP(1-4).
Solid films of ladder-type polymers on quartz plates used
for UV-vis and fluorescence were prepared by spin-coating
from a 1% THF solution at 1500 rpm. All polymers formed
homogeneous films. The UV-vis and photoluminescence
spectra of HLP(1-4) are shown in Figure 6. The absorption
maxima of the ladder-type polymers in thin films were
almost identical with those in solution, which indicates that
there was nearly no change in conformation of the ladder-
type backbone from the solution to the solid state. However,
the PL spectra of the ladder-type polymers showed slightly
difference when changing from solution to films. Compared
with the corresponding to those in solution emission spectra,
the peaks of the polymers HLP1, HLP2, and HLP3 in solid
state showed increasing red-shift values of 3, 5, and 9 nm,
respectively. The peak of the polymer HLP4 shows a red-
shift value of 5 nm. There is slight increase in the intensity
Figure 3. TGA traces of hyperbranched ladder-type polymers HLP-
(1-4).
Figure 4. UV-vis absorption and PL spectra of hyperbranched ladder-type polymers HP(1-4) in THF.

Article
Macromolecules, Vol. 43, No. 2, 2010 735
Figure 5. UV-vis absorption and PL spectra of hyperbranched ladder-type polymers HLP(1-4) in THF.
Figure 6. UV-vis absorption and PL spectra of hyperbranched ladder-type polymers HLP(1-4) in film.
Table 2. HOMO and LUMO Energies and Band Gap Data of
Hyperbranched Ladder-Type Polymers HLP(1-4)
polymers
HLP1
HLP2
HLP3
HLP4
HOMO (eV)
LUMO (eV)
band gap (eV)
-5.70
-2.79
2.91
-5.68
-2.91
2.77
-5.66
-2.95
2.71
-5.60
-2.97
2.63
around shoulder peak and tail rand emissions in films, which
is ascribed to the stronger self-absorption effect than that in
solution. Generally, the low-energy emission from the fluor-
enone defects around 550-570 nm was enhanced in the film
compared to the corresponding solution because of the
increasing interchain energy transfer. However, in the PL
spectra of HLP(1-4) in solid film, no low-energy tailed
peaks was observed. These results indicate that there is
barely any fluorenone defect or aggregation in the hyper-
branched ladder-type polymers.
Electrochemical Properties. The electrochemical behaviors
of polymers HLP(1-4) were investigated by cyclic voltammetry
(CV) with a standard three-electrode electrochemical cell in
acetonitrile solution containing 0.1 M tetrabutylammonium
hexafluorophosphate (TBAPF6) at room temperature. The oxi-
dation potentials were measured versus Ag/AgNO3 as the
reference electrode and a standard ferrocene/ferrocenium redox
system as the internal standard for estimating the HOMO of the
ladder-type polymers films. Figure 7 shows the cyclic voltammo-
grams of ladder-type polymers HLP(1-4) in films at a scan rate
of 30 mV s-1 in the range of 0-1.4 V. All the polymers films
Figure 7. Cyclic voltammograms of hyperbranched ladder-type poly-
mers HLP(1-4) in films at a scan rate of 30 mV s-1
.
showed irreversible p-doping processes in the first redox cycle.
With increasing linear length, the oxidation peaks of the polymers
moved to more negative values. The band gap (ΔE) of polymers
HLP(1-4) was calculated from the UV-vis absorption onset of
the films. The LUMO levels were calculated according to the
following equation: ELUMO = EHOMO þ Egap. The results are
summarized in Table 2. With the increase in the linear length of
the ladder polymers, the band gap becomes narrower.

736 Macromolecules, Vol. 43, No. 2, 2010
Wu et al.
Conclusion
was refluxed for 1 day under stirring. Water and CH2Cl2 (50
mL) was added, the organic layer separated, the aqueous layer
extracted with CH2Cl2 (ꢀ2), and the combined organic layers
dried over Na2SO4. Removal of the solvent, the crude product
was chromatographically purified on silica gel eluting with
CH2Cl2/hexane (1:1, v/v) increasing to CH2Cl2 to afford MA2
as a white solid (0.11 g, 30%). 1H NMR (400 MHz, CDCl3): δ
7.77 (d, 4H), 7.67 (s, 2H), 7.56 (d, 4H), 7.30 (d, 4H), 7.12 (d, 4H),
7.10 (s, 2H), 2.69 (t, 4H), 2.58 (t, 4H), 1.64 (m, 4H), 1.56 (m, 4H),
1.32-1.26 (m, 32H), 0.88-0.84 (m, 12H). 13C NMR (100 MHz,
CDCl3): δ 195.9, 195.0, 151.6, 150.6, 150.0, 142.9, 141.9, 139.7,
138.3, 134.6, 133.8, 133.1, 130.8, 130.5, 129.3, 128.9, 118.7, 36.6,
36.4, 32.1, 31.3, 31.2, 29.6, 29.6, 29.4, 29.4, 23.0, 14.4. MALDI-
TOF, m/z: calcd, 1197.3; found, 1219.9 (Mþ þ 23).
We have successfully prepared a series of ladder-type hper-
branched polymers (HLP1, HLP2, HLP3, and HLP4) via the
palladium-catalyzed Suzuki couplingreaction by an “A2 þ B3” or
“A2 þ B3 þ B2” approach. These ladder hyperbranched polymers
are soluble in common organic solvents, and their weight-average
molecular weights (Mw) were (6.93-40.7) ꢀ 104 g/mol with
polydispersity indexes (PDI) being in the range of 1.75-4.71.
All the polymers give strong pure blue emission both in solutions
and in film states and exhibit well-resolved absorption and
emission spectra, which are the characteristics of full ladder-type
polymer.
MA3. A mixture of MA1 (2.0 g, 3.1 mmol), 2,7-bis(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dihexylfluorene (MB2)
(0.1 mg, 0.16 mmol), NaHCO3 (0.4 g, 4.8 mmol), H2O (4 mL),
and THF (20 mL) was carefully degassed before Pd(PPh3)4 (8 mg,
0.082 mmol) was added. The mixture was refluxed for 1 day under
stirring. Water and CH2Cl2 (50 mL) was added, the organic layer
separated, the aqueous layer extracted with CH2Cl2 (ꢀ2), and the
combined organic layers dried over Na2SO4. After removal of the
solvent, the crude product was chromatographically purified on
silica gel eluting with CH2Cl2/hexane (1:1, v/v) to afford MA3 as a
white solid (0.10 g, 43%). 1H NMR (400 MHz, CDCl3): δ 7.82 (d,
4H), 7.70 (s, 2H) 7.59 (d, 4H), 7.45-7.42 (d, 4H), 7.31 (d, 4H), 7.22
(d, 2H), 7.16 (s, 2H), 7.06 (d, 2H), 2.68 (t, 4H), 2.53 (t, 4H),
1.64-1.52 (m, 12H), 1.32-1.12 (m, 48H), 0.93-0.80 (m, 22H),
0.26 (s, 4H). 13C NMR (100 MHz, CDCl3): δ 194.6, 193.7, 151.6,
150.5, 149.7, 142.7, 141.9, 140.4, 140.3, 137.5, 134.0, 133.6, 132.7,
130.8, 130.5, 130.4, 130.2, 129.1, 128.7, 127.8, 123.6, 120.3, 118.2,
55.2, 40.2, 36.4, 36.2, 32.0, 31.9, 31.2, 31.0, 30.3, 29.7, 29.5, 29.3,
29.3, 29.2, 23.8, 22.8, 14.3. MALDI-TOF, m/z: calcd, 1509.8;
found, 1532.0 (Mþ þ 23).
Experimental Section
General. All chemicals were purchased from Aldrich or Acros
and used without further purification. 2,7-Bis(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolan-2-yl)-9,9-dihexylfluorene,12 1,4-benzene-
diboronic, and 2,7,12-triiodohexaethyltruxene11f were prepared ac-
cording to literature procedures. The catalyst precursor Pd(PPh3)4
was prepared according to the literature13 and stored in a Shlenk
tube under nitrogen. All solvents were purified and dried by standard
methods. The reactions were monitored by TLC with silica gel
60 F254 (Merck, 0.2 mm). Column chromatography was carried
out on silica gel (200-300 mesh). 1H and 13C NMR spectra were
recorded on a Bruker AV400 spectrometer in CDCl3. The electro-
chemical behavior of compounds was investigated by using
cyclic voltammetry (CHI 630A electrochemical analyzer) with a
standard three-electrode electrochemical cell in a 0.1 M tetrabutyl-
ammonium tetrafluoroborate solution in CH3CN at room tempera-
ture at atmospheric pressure with a scanning rate of 30 mV s-1
.
A glassy carbon working electrode, a Pt wire counter electrode,
and an Ag/AgNO3 (0.01 M in CH3CN) reference electrode were
used. The experiments were calibrated with the standard ferrocene/
ferrocenium (Fc) redox system and assumption that the energy level
of Fc is 4.8 eV below vacuum. Electronic absorption spectra were
obtained on a Shimadzu UV-vis spectrometer model UV-2500.
Fluorescence spectra were recorded on a Shimadzu RF-5301PC.
Elemental analyses were performed on a Flash EA 1112 analyzer.
TGA (Pyris 1 TGA) and DSC (TA 2910) measurements were
carried out under a nitrogen atmosphere at a heating rate of
10 °C/min to recorded the thermal gravimetric analysis (TGA)
and differential scanning calorimetry (DSC), respectively. The ma-
trix-assisted laser desorption ionization time-of-flight (MALDI-
TOF) MS spectrometric measurements were performed on a Bruker
BIFLEXIII mass spectrometer.
MB2. A mixture of 2,7,12-triiodohexaethyltruxene (1.0 g,
0.82 mmol), bis(pinacolato)diboron (1.4 g, 5.5 mmol), CH3-
COOK (0.61 g, 6.2 mmol), and DMF (30 mL) was carefully
degassed before Pd(dppf)2Cl2 (50 mg, 0.082 mmol) was added.
The mixture was stirred for 24 h at 90 °C unde N2. Water and
CH2Cl2 (300 mL) were added, and the organic layer was
separated and washed with water three times. After removal
of the solvent, the crude product was chromatographically
purified on silica gel eluting with CH2Cl2/hexane (1:3, v/v) to
afford MB2 as a white solid (0.54 g, 54%). 1H NMR (400 MHz,
CDCl3): δ 8.38 (d, 3H), 7.87 (d, 3H), 7.85 (s, 3H), 2.92 (m, 6H),
2.15 (m, 6H), 1.42 (s, 36H), 0.88-0.80 (m, 36H), 0.58 (t, 18H),
0.44 (m, 12H). 13C NMR (100 MHz, CDCl3): δ 153.0, 146.7,
143.4, 138.6, 133.1, 128.4, 124.2, 83.9, 56.0, 37.1, 31.2, 29.7, 25.2,
24.2, 22.5, 14.1. Anal. Calcd for C81H123B3O6: C, 79.40; H,
10.12. Found: C, 79.38; H, 10.15.
General Procedure for the Synthesis of Hyperbranched Poly-
mers HP(1-4). A mixture of the respective monomers, K2CO3,
THF, and H2O was degassed, and Pd(PPh3)4 was added under a
nitrogen atmosphere. The reaction mixture was heated at reflux
and stirred under nitrogen for 3 days. 1-Bromo-4-methylben-
zene (50 mg, 0.29 mmol) was added to cap the bronic end groups.
After refluxing for another 24 h, water and CH2Cl2 (200 mL)
were added, the organic layer was separated, and the organic
layer was dried over Na2SO4. After removal of most of the
solvent, the residue was precipitated in methanol. The crude
polymers were repurified by precipitation from THF into
hexane again and dried under vacuum to give polymers HP-
(1-4).
Synthesis of Monomers and Polymers. MA1. 2,5-Dibromo-
terephthalic acid (3.0 g, 10.5 mmol) was treated with 20 mL of
thionyl chloride (SOCl2) (20 mL) and refluxed for 10 h. The
excess SOCl2 was removed in a vacuum to give 3,6-dibromo-2,5-
phenylenendi(carboxylic acid chloride) as a crystalline yellow
solid.
To a solution of heptylbenzene (7.0 mL) and aluminum
trichloride (1.8 g, 13.5 mmol), a mixture of all product and
6 mL of CH2Cl2 was added dropwise. After stirring at room
temperature for 2 h the mixture was poured into ice. The organic
layer was washed with 1 M NaOH and water, then dried over
Na2SO4, and concentrated. The residue was chromatographi-
cally purified on silica gel eluting with CH2Cl2/hexane (1:2) to
afford MA1 as a white crystal (total yield: 4.5 g, 76%). 1H NMR
(400 MHz, CDCl3): δ 7.76 (d, 4H), 7.58 (s, 2H) 7.31 (d, 4H), 2.69
(t, 4H), 1.65 (t, 14H), 1.32-1.28 (m, 16H), 0.88 (t, 6H). 13C
NMR (100 MHz, CDCl3): δ 193.6, 150.8, 143.6, 133.1, 130.7,
129.2, 118.7, 36.4, 32.0, 31.2, 29.5, 29.3, 22.9, 14.3. Anal. Calcd
for C34H40Br2O2: C, 63.76; H, 6.29. Found: C, 63.75; H, 6.24.
MA2. A mixture of MA1 (2.0 g, 3.1 mmol), 1,4-benzenedi-
boronic pinacol ester (0.1 g, 0.3 mmol), NaHCO3 (0.4 g, 4.8
mmol), H2O (4 mL), and THF (20 mL) was carefully degassed
before Pd(PPh3)4 (8 mg, 0.082 mmol) was added. The mixture
Hyperbranched Polymer HP1. MA1 (63 mg, 0.098 mmol),
MB2 (120 mg, 0.098 mmol), K2CO3 (0.30 g, 2.2 mmol), H2O(3
mL), THF (15 mL), and Pd(PPh3)4 (8 mg, 0.0069 mmol) were
used. HP1 was obtained as yellow-green solid (0.13 g, 94%). 1H
NMR (400 MHz, CDCl3): δ 8.19 (broad, 3H), 7.78-7.65
(broad, 10H) 7.53-7.63 (broad, 4H), 7.36 (broad, 2H), 7.10
(broad, 4H), 2.83-2.72 (broad, 6H), 2.53-2.40 (broad, 7H),

Article
Macromolecules, Vol. 43, No. 2, 2010 737
2.10-1.86 (broad, 6H), 1.68 (broad, 4H), 1.24 (broad, 16H),
0.84 (broad, 42H), 0.59-0.26 (broad, 30H). Anal. Calcd for
7.26-6.84 (broad, 24H), 3.92 (broad, 8H), 2.95-2.80 (broad,
6H), 2.59-2.45 (broad, 11H), 2.34-2.09 (broad, 10H),
1.86-1.43 (broad, 16H), 1.26 (broad, 92H), 0.87-0.34 (broad,
100H). Anal. Calcd for C223H294O4: C, 88.14; H, 9.75. Found: C,
83.59; H, 9.61.
Hyperbranched Ladder-Type Polymer HLP4. A yellow solid
(48 mg, 58%). 1H NMR (400 MHz, CDCl3): δ 8.20-8.10 (broad,
1H), 7.65-7.54 (broad, 8H), 7.47-7.26 (broad, 4H), 7.26-6.80
(broad, 12H), 3.91 (broad, 4H), 2.95-2.70 (broad, 2H), 2.57-2.45
(broad, 7H), 2.38-2.00 (broad, 5H), 1.91-1.64 (broad, 8H),
1.28-1.12 (broad, 36H), 0.88-0.30 (broad, 51H). Anal. Calcd
for C101H134O2: C, 87.90; H, 9.79. Found: C, 83.29; H, 9.99.
C
104H134O2: C, 88.20; H, 9.54. Found: C, 85.78; H, 9.45.
Hyperbranched Polymer HP2. MA2 (100 mg, 0.084 mmol),
MB2 (102 mg, 0.084 mmol), K2CO3 (0.30 g, 2.2 mmol), H2O
(3 mL), THF (15 mL), and Pd(PPh3)4 (9 mg, 0.0078 mmol) were
used. HP2 was obtained as yellow-green solid (0.15 g, 91%). 1H
NMR (400 MHz, CDCl3): δ 8.25-8.10 (broad, 3H), 7.71-7.66
(broad, 10H), 7.48-7.26 (broad, 14H), 7.12 (broad, 10H), 2.83
(broad, 6H), 2.58-2.44 (broad, 11H), 2.09-1.85 (broad, 6H),
1.56 (broad, 8H), 1.27 (broad, 32H), 0.87-0.85 (broad, 48H),
0.57 (broad, 18H), 0.27 (broad, 12). Anal. Calcd for C144H178O4:
C, 87.66; H, 9.09. Found: C, 85.82; H, 9.05.
Hyperbranched Polymer HP3. MA3 (100 mg, 0.066 mmol),
MB2 (84 mg, 0.066 mmol), K2CO3 (0.30 g, 2.2 mmol), H2O
(3 mL), THF (15 mL), and Pd(PPh3)4 (8 mg, 0.0069 mmol) were
used. HP3 was obtained as yellow-green solid (0.14 g, 92%). 1H
NMR (400 MHz, CDCl3): δ 8.20-8.05 (broad, 3H), 7.71-7.65
(broad, 12H), 7.48-7.26 (broad, 14H), 7.12 (broad, 10H),
2.83-2.70 (broad, 6H), 2.51-2.43 (broad, 11H), 2.08-1.72
(broad, 10H), 1.56 (broad, 8H), 1.27 (broad, 32H), 0.99-0.83
(broad, 68H), 0.58 (broad, 24H), 0.33 (broad, 16H). Anal. Calcd
for C167H214O4: C, 87.76; H, 9.44. Found: C, 87.23; H, 9.47.
Hyperbranched Polymer HP4. MA1 (100 mg, 0.16 mmol),
MB1 (75 mg, 0.12 mmol), MB2 (47 mg, 0.038 mmol), K2CO3
(0.30 g, 2.2 mmol), H2O (3 mL), THF (15 mL), and Pd(PPh3)4
(8 mg, 0.0069 mmol) were used. HP4 was obtained as yellow-
green solid (0.15 g, 96%). 1H NMR (400 MHz, CDCl3):
δ 8.20-8.10 (broad, 1H), 7.66-7.55 (broad, 8H), 7.46 (broad,
4H), 7.31-7.26 (broad, 2H), 7.05 (broad, 4H), 2.80-2.70
(broad, 2H), 2.50-2.37 (broad, 7H), 2.08-1.67 (broad, 5H),
1.50 (broad, 4H), 1.22 (broad, 16H), 0.99-0.84 (broad, 24H),
0.59-0.32 (broad, 15H). Anal. Calcd for C73H94O2: C, 87.37; H,
9.44. Found: C, 86.55; H, 9.27.
Acknowledgment. This work was supported by Nature
Science Foundation of China Grants 20904008 and 20574016
and the Science Research Project of the Department of Education
of Hebei Province 2009307.
References and Notes
(1) (a) Burroughes, J. H.; Bradley, D. D. C.; Brown, A. B.; Marks,
R. N.; Mackay, K.; Friend, R. H.; Burn, P. L.; Holmes, A. B.
Nature 1990, 347, 539. (b) Kraft, A.; Grimsdale, A. C.; Holmes, A. B.
Angew. Chem., Int. Ed. 1998, 37, 402. (c) M€uller, C. D.; Falcou, A.;
Reckefuss, N.; Rojahn, M.; Wiederhirn, V.; Rudati, P.; Frohne, H.;
Nuyken, O.; Becker, H.; Meerholz, K. Nature 2003, 421, 829. (d)
Akcelrud, L. Prog. Polym. Sci. 2003, 28, 875.
(2) (a) Jiang, X. Z.; Liu, S.; Ma, H.; Jen, A. K. Y. Appl. Phys. Lett.
2000, 76, 1813. (b) Kim, D. Y.; Cho, H. N.; Kim, C. Y. Prog. Polym.
Sci. 2000, 25, 1089.
(3) (a) Pei, Q.; Yang, Y. J. Am. Chem. Soc. 1996, 118, 7416. (b) Bernius,
M. T.; Inbasekaran, M.; O'Brien, J.; Wu, W. Adv. Mater. 2000, 12,
1737. (c) Neher, D. Macromol. Rapid Commun. 2001, 22, 1365. (d)
Scherf, U.; List, E. J. W. Adv. Mater. 2002, 14, 477. (e) Leclerc, M. J.
Polym. Sci., Part A: Polym. Chem. 2001, 39, 2867. (f) Li, J.; Bo, Z. S.
Macromolecules 2004, 37, 2013.
General Procedure for the Synthesis of Hyperbranched Poly-
mers HLP(1-4). 4-Octyloxybenzene lithium (5 mL, 3.5 mmol)
in ether was dropped into the solution of THF (30 mL) and
polymer (60 mg) at 0 °C under nitrogen, and the mixture was
stirred for 5 min at 0 °C. Water and CH2Cl2 (100 mL) were
added, the organic layer was separated, and the aqueous layer
was extracted with CH2Cl2 (ꢀ2). The combined organic layers
were dried over Na2SO4 and concentrated to dryness. The crude
polymer was precipitated from THF into hexane. The precipita-
tion was dissolved in dry CH2Cl2 (20 mL) and treated with
€
(4) (a) Scherf, U.; Mullen, K. Makromol. Chem. Rapid Commun. 1991,
12, 489. (b) Scherf, U.; M€ullen, K. Macromolecules 1992, 25, 3546. (c)
Scherf, U.; M€ullen, K. Adv. Polym. Sci. 1995, 123, 1. (d) Grimsdale,
A. C.; M€ullen, K. Adv. Polym. Sci. 2006, 199, 1. (e) Scherf, U. J.
Mater. Chem. 1999, 9, 1853. (f) Grimme, J.; Scherf, U. Macromol.
Chem. Phys. 1996, 197, 2297. (g) Schindler, F.; Jacob, J.; Grimsdale,
A. C.; Scherf, U.; M€ullen, K.; Lupton, J. M.; Feldmann, J. Angew.
Chem., Int. Ed. 2005, 44, 1520l. (h) Jacob, J.; Sax, S.; Gaal, M.; List,
E. J. W.; Grimsdale, A. C.; M€ullen, K. Macromolecules 2005, 38, 9933.
(i) Mishra, A. K.; Graf, M.; Grasse, F.; Jacob, J.; List, E. J. W.; M€ullen,
K. Chem. Mater. 2006, 18, 2879. (j) Xia, C.; Advincula, R. C.
Macromolecules 2001, 34, 6922. (k) Liu, L. L.; Qiu, S.; Wang, B. L.;
Zhang, W.; Lu, P.; Xie, Z. Q.; Hanif, M.; Ma, Y. G.; Shen, J. C. J. Phys.
Chem. B 2005, 109, 23366. (l) Qiu, S.; Lu, P.; Shen, F. Z.; Liu, L. L.;
Ma, Y. G.; Shen, J. C. Macromolecules 2003, 36, 9823.
BF3 ether (0.4 g, 2.61 mmol). After stirring for 5 min at room
3
temperature, 10 mL of ethanol was added to the mixture to
destroy the catalyst. Water and CH2Cl2 (100 mL) were added,
and the organic layer was separated and washed with water three
times, dried over Na2SO4, and concentrated to dryness. The
crude polymer was precipitated from THF into methanol to give
hyperbranched ladder-type polymers.
(5) (a) Sainova, D.; Miteva, T.; Nothofer, H. G.; Scherf, U.; Glowacki,
I.; Ulanski, J.; Fujikawa, H.; Neher, D. Appl. Phys. Lett. 2000, 76,
1810. (b) Zeng, G.; Yu, W. L.; Chua, S. J.; Huang, W. Macromolecules
2002, 35, 6907. (c) Craig, M. R.; de Kok, M. M.; Hofstraat, J. W.;
Schenning, A. P. H. J.; Meijer, E. W. J. Mater. Chem. 2003, 13, 2861.
(d) Romaner, L.; Pogantsch, A.; Scandiucci de Freitas, P.; Scherf, U.
Adv. Funct. Mater. 2003, 13, 597. (e) Zojer, E.; Pogantsch, A.;
Hennebicq, E.; Beljonne, D.; Bredas, J. L.; de Freitas, P. S.; Scherf,
U.; List, E. J. W. J. Chem. Phys. 2002, 117, 6794. (f) List, E. J. W.;
Guentner, R.; Scandiucci de Freitas, P.; Scherf, U. Adv. Mater. 2002,
14, 374. (g) Kulkarni, A. P.; Kong, X.; Jenekhe, S. A. J. Phys. Chem. B
2004, 108, 8689.
Hyperbranched Ladder-Type Polymer HLP1. A slightly yel-
low solid (58 mg, 76%). 1H NMR (400 MHz, CDCl3): δ
8.25-8.05 (broad, 3H), 7.74-7.65 (broad, 8H), 7.52-7.33
(broad, 8H), 7.26-6.85 (broad, 10H), 3.99-3.92 (broad, 4H),
2.80-2.74 (broad, 6H), 2.74-2.45 (broad, 7H), 2.18-2.03
(broad, 6H), 1.85-1.68 (broad, 8H), 1.60-1.12 (broad, 36H),
0.88-0.28 (broad, 78H). Anal. Calcd for C132H174O2: C, 88.43;
H, 9.78. Found: C, 85.84; H, 9.68.
(6) (a) Lemmer, U.; Heun, S.; Mahrt, R. F.; Scherf, U.; Hopmerier,
Hyperbranched Ladder-Type Polymer HLP2. A slightly yel-
low solid (52 mg, 63%). 1H NMR (400 MHz, CDCl3): δ
8.25-8.10 (broad, 3H), 7.68-7.65 (broad, 12H), 7.52-7.26
(broad, 10H), 7.26-6.83 (broad, 24H), 3.93 (broad, 8H),
2.96-2.83 (broad, 6H), 2.84-2.58 (broad, 11H), 2.29-2.03
(broad, 6H), 1.76-1.41 (broad, 16H), 1.26 (broad, 72H),
0.87-0.34 (broad, 90H). Anal. Calcd for C200H258O4: C,
88.11; H, 9.54. Found: C, 84.33; H, 9.25.
€
€
€
M.; Siegner, U.; Gobel, E. O.; Mu llen, K.; Bassler, H. Chem. Phys.
Lett. 1995, 240, 373. (b) Graupner, W.; Eder, S.; Tasch, S.; Leising, G.;
Lanzani, G.; Nisoi, M.; de Silvestri, S.; Scherf, U. J. Fluoresc. 1995, 7,
195s. (c) Mahrt, R. F.; Pauck, T.; Lemmer, U.; Siegner, U.; Hopmeier,
€
€
M.; Hennig, R.; Bassler, H.; Gobel, E. O.; Haring Bolivar, P.; Wegmann,
G.; Kurz, H.; Scherf, U.; M€ullen, K. Phys. Rev. 1996, 54, 1759.
(7) (a) Shu, C. F.; Dodda, R.; Wu, F. I.; Liu, M. S.; Jen, A. K. Y.
Macromolecules 2003, 36, 6698. (b) Ego, C.; Grimsdale, A. C.; Uckert,
F.; Yu, G.; Srdanov, G.; M€ullen, K. Adv. Mater. 2002, 14, 809. (c)
Marsitzky, D.; Scott, J. C.; Chen, J. P.; Lee, V. Y.; Miller, R. D.;
Setayesh, S.; M€ullen, K. Adv. Mater. 2001, 13, 1096. (d) Yu, W. L.; Pei,
J.; Huang, W.; Heeger, A. J. Adv. Mater. 2000, 12, 828. (e) Zhan, X. W.;
Hyperbranched Ladder-Type Polymer HLP3. A yellow solid
(60 mg, 75%). 1H NMR (400 MHz, CDCl3): δ 8.25-8.10
(broad, 3H), 7.69-7.63 (broad, 12H), 7.53-7.26 (broad, 12H),

738 Macromolecules, Vol. 43, No. 2, 2010
Wu et al.
Wang, S.; Liu, Y. Q.; Wu, X.; Zhu, D. B. Chem. Mater. 2003, 15, 1963.
(f) Xia, C. J.; Advincula, R. Macromolecules 2001, 34, 5854. (g)
Miteva, T.; Meisel, A.; Knoll, W.; Nothofer, H. G.; Scherf, U.; M€uller,
D. C.; Meerholz, K.; Yasuda, A.; Neher, D. Adv. Mater. 2001, 13, 565.
(h) Setayesh, S.; Grimsdale, A. C.; Wei, T.; Enkelmann, V.; M€ullen, K.;
Meghdadi, F.; List, E. J. W.; Leising, G. J. Am. Chem. Soc. 2001, 123,
946. (i) Pogantsch, A.; Wenzl, F. P.; List, E. J. W.; Leising, G.;
Grimsdale, A. C.; M€ullen, K. Adv. Mater. 2002, 14, 1061. (j)
Marsitzky, D.; Vestberg, R.; Blainey, P.; Tang, B. T.; Hawker, C. J.;
Carter, K. R. J. Am. Chem. Soc. 2001, 123, 6965. (k) Chou, C. H.; Shu,
C. F. Macromolecules 2002, 35, 9673.
(9) Wang, P. W.; Liu, Y. J.; Devadoss, C.; Bharathi, P.; Moore, J. S.
Adv. Mater. 1996, 8, 237.
€
ꢀ
(10) (a) Gomez-Lor, B.; de Frutos, OA.; Echavarren, A. M. Chem.
Commun. 1999, 2431. (b) Abdourazak, A. H.; Marcinow, Z.; Sygula,
A.; Sygula, R.; Rabideau, P. W. J. Am. Chem. Soc. 1995, 117, 6410. (c)
€
€
ꢀ
ꢀ
de Frutos, OA.; Gomez-Lor, B.; Granier, T.; Monge, M. AA.; Gutierrez-
Puebla, E.; Echavarren, A. M. Angew. Chem., Int. Ed. 1999, 38, 204.
(d) Jacob, K.; Sigalov, M.; Becher, J. Y.; Ellern, A.; Khodorkovsky, V.
Eur. J. Org. Chem. 2000, 11, 2047. (e) Cao, X.Y.; Zhang, W. B.; Wang,
J. L.; Zhou, X. H.; Lu, H.; Pei, J. J. Am. Chem. Soc. 2003, 125, 12430.
(f) Kimura, M.; Kuwano, S.; Sawaki, Y.; Fujikawa, H.; Noda, K.; Taga,
Y.; Takagi, K. J. Mater. Chem. 2005, 15, 2393.
(8) (a) Kim, Y. H. J. Polym. Sci., Part A: Polym. Chem. 1998, 36, 1685.
(b) Voit, B. J. J. Polym. Sci., Part A: Polym. Chem. 2000, 38, 2505.
(c) Chen, J.; Peng, H.; Law, C. C. W.; Dong, Y.; Lam, J. W. Y.; Williams,
I. D.; Tang, B. Z. Macromolecules 2003, 36, 4319. (d) Kang, S. H.; Luo,
J.; Ma, H.; Barto, R. R.; Frank, C. W.; Dalton, L. R.; Jen,
A. K. Y. Macromolecules 2003, 36, 4355. (e) Furuta, P.; Brooks, J.;
(11) (a) Pei, J.; Wang, J. L.; Cao, X. Y.; Zhou, X. H.; Zhang, W. B. J.
Am. Chem. Soc. 2003, 125, 9944. (b) Cao, X. Y.; Zhang, W. B.; Wang,
J. L.; Zhou, X. H.; Lu, H.; Pei, J. J. Am. Chem. Soc. 2003, 125, 12430.
(c) Duan, X. F.; Wang, J. L.; Pei, J. Org. Lett. 2005, 7, 4071. (d)
Kanibolotsky, A. L.; Berridge, R.; Skabara, P. J.; Perepichka, I. F.;
Bradley, D. D. C.; Koeberg, M. J. Am. Chem. Soc. 2004, 126, 13695.
(e) Zheng, Q. D.; He, G. S.; Prasad, P. N. Chem. Mater. 2005, 17, 6004.
(f) Cao, X. Y.; Zhou, X. H.; Zi, H.; Pei, J. Macromolecules 2004, 37,
8874.
ꢀ
Thompson, M. E.; Frechet, J. M. J. J. Am. Chem. Soc. 2003, 125,
13165. (f) Hahn, U.; Gorka, M.; Vogtle, F.; Vicinelli, V.; Ceroni, P.;
Maestri, M.; Balzani, V. Angew. Chem., Int. Ed. 2002, 41, 3595. (g)
Pogantsch, A.; Wenzl, F. P.; List, E. J. W.; Leising, G.; Grimsdale, A. C.;
M€ullen, K. Adv. Mater. 2002, 12, 1061. (h) Lupton, J. M.; Samuel,
(12) Chen, H.; He, M. Y.; Pei, J.; Liu, B. Anal. Chem. 2002, 74, 6252.
(13) Tolman, C. A.; Seidel, W. C.; Gerlach, D. H. J. Am. Chem. Soc.
1972, 94, 2669.
€
I. D. W.; Beavington, R.; Burn, P. L.; Bassler, H. Adv. Mater. 2001, 13,
258. (i) Li, J.; Bo, Z. S. Macromolecules 2004, 37, 2013.