Synthesis and characterization of spiro-triphenylamine configured polyfluorene derivatives with improved hole injection

Article abstract of DOI:10.1021/ma060683o

We report on the synthesis of a spiro-fluorene derivative with bulky tert-butyl-substituted triphenylamine structure. The compound was synthesized in an attempt to enhance both hole injection and physical properties. A series of copolymers of the compound

Full text of DOI:10.1021/ma060683o

Macromolecules 2006, 39, 6433-6439
6433
Synthesis and Characterization of Spiro-Triphenylamine Configured
Polyfluorene Derivatives with Improved Hole Injection
Doojin Vak,† Jang Jo,† Jieun Ghim,† Chaemin Chun,† Bogyu Lim,†
Alan J. Heeger,†,‡ and Dong-Yu Kim*,†
Heeger Center for AdVanced Materials, Gwangju Institute of Science and Technology, 1 Oryong-dong,
Buk-gu, Gwangju, Korea, and Physics Department and Materials Department, UniVersity of California,
Santa Barbara, California 93106
ReceiVed March 26, 2006; ReVised Manuscript ReceiVed July 13, 2006
ABSTRACT: We report on the synthesis of a spiro-fluorene derivative with bulky tert-butyl-substituted
triphenylamine structure. The compound was synthesized in an attempt to enhance both hole injection and physical
properties. A series of copolymers of the compound and a spiro-anthracenefluorene structure were synthesized,
and their physical, optical, and electrochemical characteristics were investigated. The polymers showed good
thermal stability with decomposition temperatures in excess of 389 °C and high glass transition temperatures in
the range of 112-207 °C. The emission characteristics of the polymers were similar to that of dialkyl polyfluorenes.
Cyclic voltametry studies revealed that the energy level of polymers can be tuned by adjusting the
spiro-triphenylamine content with a tuning range of about 0.5 eV. Organic light-emitting diodes were fabricated
using the polymers. All of the devices showed an emission in the deep blue region, and the copolymers showed
improved hole injecting/transporting characteristics.
Conjugated polymers have attracted considerable research
interest in the past decade due to their potential applications in
the areas of large area plat panel display and other optoelectronic
devices.1,2 Organic light-emitting diodes (OLEDs) are promising
devices for use in full color plat panel displays and have a
number of advantages over conventional devices such as a low
driving voltage, wide viewing angle, thin film structure, and a
simpler manufacturing process.3 Polymer-based OLEDs have
a considerable potential for use in flexible displays.4 Various
conjugated polymers have been developed for such applications.
Among them, polyfluorene derivatives (PFs) have generated
considerable interest as blue-emitting materials due to their high
photoluminescence (PL) efficiency, wide band gap for blue
emission, and thermal stability.5-9 In addition, the ability to
readily functionalize the C-9 position of the fluorene unit is
one of the advantages of these types of compounds. Various
solublizing alkyl chains or side groups have been introduced at
this position. However, the C-9 position of the fluorene unit
recently has been regarded as a problem. List et al. reported
that the degradation of blue emission of PFs was due to
oxidation of the C-9 position to form fluorenone, the emission
of which is similar to the broad band emission of degraded PFs,
in conjugated backbones the so-called keto defect.10 Keto defects
can be formed not only by photoirradiation or heat treatment
but during the operation of device via electrooxidation. The
appearance of a broad band emission of PFs in the green region,
the so-called g-band, constitutes an important issue in terms of
enhancing OLED lifetime and has been attributed to a physical
defect, aggregate formation followed by excimer emission.11-15
The results of more recent studies suggest that this can be
attributed to chemical degradation.16-19 Although keto defects
are currently believed to be the most probable source of long
wavelength emission, the chemical defect model does not
completely explain some phenomena such as the enhanced
stability by cross-linking,20,21 copolymerization with bulky
groups,22 blending,23 introduction of complex backbone struc-
tures,24 the dependency on the length of alkyl groups,25 and the
increase in long wavelength emission in the solution state by
enhanced molecular interaction.26 Therefore, both models are
needed to completely explain all of the experimental observa-
tions. Although the major reason for the appearance of g-bands
is still not clear, most previous reports have concluded that the
introduction of bulky phenyl side groups instead of long alkyl
chains can effectively suppress the degradation phenomenon.27-35
The reason for this is that bulky phenyl side groups not only
enhance physical properties in a fully amorphous state and
enhance glass transition temperature of polymers followed by
reduced aggregate formation but also enhance the chemical
stability toward oxidative degradation due to the more stable
C(sp2)-C(sp2) bonds at the C-9 position of fluorene units
compared to the C(sp2)-C(sp3) bonds of conventional alkyl-
substituted PFs.
One of the useful bulky phenyl side groups is a fluorene unit
itself connected by a spiro-linkage, referred to as a spiro-
bifluorene. A spiro-bifluorene contains two biphenyl units
connected by a tetrahedrally bonded carbon atom, in which the
planes of the biphenyl units lie perpendicular to each other. Once
incorporated into PFs, this three-dimensional structure should
prevent the approach of other polymer backbones, and therefore
aggregate formation of the conjugated polymer backbone would
be minimized efficiently. Although the introduction of a spiro-
bifluorene into PF has been shown to alleviate the spectral
stability problem,32 its incorporation into the polymer structure
greatly reduces its solubility in common organic solvents. As a
result, no homopolymer of spiro-bifluorene has been reported.
We recently reported on poly[10,10-bis(2-ethylhexyl)-10H-
spiro(anthracene-9,9′-fluorene)-2′,7′-diyl] (PEHSAF), which
contains a spiro-anthracenefluorene (SAF) rather than a spiro-
bifluorene.33 The SAF structure still contains the useful spiro-
structure and, at the same time, permits the facile functional-
† Gwangju Institute of Science and Technology.
‡ University of California, Santa Barbara.
* Corresponding author: Tel +82-62-970-2319, Fax +82-62-970-2304,
e-mail kimdy@gist.ac.kr.
10.1021/ma060683o CCC: $33.50 © 2006 American Chemical Society
Published on Web 08/19/2006

6434 Vak et al.
Macromolecules, Vol. 39, No. 19, 2006
Chart 1
route for producing an efficient device. We recently reported
on poly[10-(4-(2-ethylhexyl)-phenyl)-2,7-bis(2-ethylhexyl)-10H-
spiro(ancridine-9,9′-fluorene)-2′,7′-diyl] (PEHSACF).42 PEH-
SACF contains spiro-triphenylamine (TPA) structure with
ethylhexyl solubilizing chains. Although the polymer adopted
both a physically stable spiro-structure and an electronically
preferred phenylamine structure, the structure contains a chemi-
cally unstable benzylic position which is susceptible to oxida-
tion.
In this article, we report on a new spiro-fluorene unit
containing spiro-TPA structure with chemically stable tert-butyl
groups and its polymers. A series of copolymers based on this
structure and hexadecyl-substituted SAF structure were syn-
thesized with various feed ratios. The thermal, optical, and
electrochemical properties of the polymers were investigated,
and OLEDs based on the polymers were fabricated and
characterized.
ization of the C-10 position of the dihydroanthracene unit. The
polymer not only showed stable photoluminescence (PL) spectra
after thermal treatment and photoirradiation but also showed
excellent characteristics as an organic laser material due to its
stable amorphous state. Bradley’s group reported that the
polymer showed an amplified spontaneous emission up to 250
°C (limited by the apparatus) with very low optical loss (loss
coefficient ) 0.8 cm-1) and PL efficiency higher than PFs.36
Although PEHSAF showed enhanced physical properties, it
still has the intrinsic problem associated with PFs. Since low
work function metals are preferred as the anode in PFs-based
OLEDs, imbalanced carrier injection continues to be a problem
because the ionization potential of PFs is -5.8 eV37 and
that of poly(ethylenedioxythiophene):poly(styrenesulfonate)
(PEDOT:PSS) is -5.2 eV.38 This indicates that a significant
energy barrier for hole injection exists, while the energy barrier
for electron injection is very small when calcium, which is one
of the most frequently used metals in large band-gap materials,
is used as a cathode. Several studies have reported improvements
in hole injecting and transporting properties when a phenylamine
structure is introduced into conjugated polymers as an end-
capper or as a side group.39-41 These reports showed that the
introduction of structures containing a heteroatom is a useful
Results and Discussion
Synthesis and Characterization of Polymers. The synthesis
of monomers is shown in Scheme 1. The bulky tert-butyl-
substituted triphenylamine was synthesized via a Friedel-Crafts
alkylation reaction. The solvent, trifluoroacetic acid, was used
for activation of tert-butyl alcohol. Because of the reduced
solubility of the alkylated TPA in the solvent compared to
nonsubstituted TPA, the product precipitated during the reaction.
Therefore, not only the reaction temperature but also the amount
of solvent used found to be was very important. After optimizing
the reaction conditions, 1 was easily obtained in high purity by
a by simple filtration process. 2 was synthesized via the well-
known highly selective bromination method.43 Although DMF
is typically used for the bromination reaction, we used dichlo-
romethane as a cosolvent due to the low solubility of 1 in DMF.
To 1 in dichloromethane solution, N-bromosuccinimide in DMF
solution was slowly added dropwise at room temperature.
Scheme 1. Synthesis of Monomers

Macromolecules, Vol. 39, No. 19, 2006
Polyfluorenes with Spiro-Triphenylamine Structure 6435
Table 2. Absorption and Emission Properties, Absolute
Photoluminescence Quantum Efficiencies and HOMO and LUMO
Energy Levels of the Polymers
Scheme 2. Polymerization of PSAF16 and PSAF Copolymers
with Different Feed Ratios
a
b
abs λmax PL λmax ΦPL
Eg
HOMOc LUMOd
polymer
(nm)
(nm)
(%)
(eV)
(eV)
(eV)
PSAF-T7
PSAF-T5
PSAF-T3
PSAF-T1
PSAF16
400
400
402
402
402
422
422
423
437
438
26
36
47
69
59
3.0
3.0
3.0
3.0
3.0
-5.36
-5.65
-5.69
-5.73
-5.84
-2.36
-2.65
-2.69
-2.73
-2.84
a PL quantum efficiencies in film measured in an integrating sphere.
b Optical band gap calculated from absorption spectra edge. c Determined
by extrapolation of oxidative CV curves. d LUMO ) HOMO + Eg.
Table 1. Molecular Weights, Glass Transition Temperature, and
Decomposition Temperatures of the Polymers
a
a
Mn
Mw
polymer
(g/mol)
(g/mol)
PDIa
Tgb (°C)
Tdc (°C)
Table 3. Characteristics of OLEDs with the Configuration of
ITO/PEDOT:PSS (40 nm)/Emitting Polymer (70 nm)/LiF (5 nm)/Ca
(30 nm)/Silver (200 nm)
PSAF-T7
PSAF-T5
PSAF-T3
PSAF-T1
PSAF16
23 000
17 000
15 000
11 000
11 000
68 000
44 000
38 000
27 000
24 000
2.95
2.58
2.53
2.45
2.18
207
165
130
112
145
404
396
392
385
389
luminance QE turn-ona
LE
PE
CIE
(x, y)
polymer
(cd/m2)
(%)
(V)
(cd/A) (m/W)
PSAF-T7
PSAF-T5
PSAF-T3
PSAF-T1
PSAF16
1298
1383
1160
912
0.07
0.13
0.19
0.21
0.13
5.9
5.4
6.1
5.1
6.2
0.11
0.19
0.25
0.28
0.19
0.07
0.07
0.09
0.12
0.07
0.196, 0.186
0.191, 0.182
0.184, 0.169
0.176, 0.150
0.183, 0.178
a Molecular weights and polydispersity index (PDI) were estimated by
GPC against polystyrene standards. b Glass transition temperature measured
by DSC under nitrogen. c Temperature resulting in a 5% weight loss based
on the initial weight.
574
a Turn-on voltage, determined as the voltage required to give a luminance
of 1 cd/m2.
Careful GC/MS analysis showed that a trace of dibromination
was occurred during the reaction. The addition of a solution of
2 in THF to flame-dried Mg, followed by refluxing for 1 h
produced the Grignard reagent of 2. The Grignard reagent was
added by 2,7-dibromofluorenone and refluxed for 2 h to produce
an intermediate of spiro-structure. The intermediate contained
a tert-alcohol at C-9 position of the fluorene unit. The C-9
position of fluorene unit was activated under acidic conditions
and reacted with the TPA part via intramolecular cyclization to
form 3. 4 was synthesized using nearly the same way for the
synthesis of an ethylhexyl-substituted SAF structure.33 An anion
was produced by the elimination of proton at the C-10 position
of dihydroanthracene structure by treatment with the strong base
KH, and the resulting anion was reacted with 1-bromoexadecane
in situ.
A series of copolymers of 3 and 4 were synthesized via
nickel-mediated polymerization using various feed ratios. The
scheme for the polymerization is shown in Scheme 2. We
attempted to synthesize a homopolymer of 3. However, because
of the low solubility of the unit, the polymer precipitated during
the polymerization reaction, resulting in polymer with a very
low molecular weight. We reported on the poly(spiro-
anthracenefluorene) (PSAF) homopolymer with ethylhexyl side
chains, PEHSAF.33 The polymer was sufficiently soluble to
permit solution processing. However, the ethylhexyl group was
not effective as a solublizing group for the copolymer of PSAF
and 4. Therefore, a hexadecyl group was introduced into the
SAF structure. All copolymers showed molecular weights higher
than tens of thousands and showed good solubility in common
organic solvents such as chloroform, toluene, and chlorobenzene.
The characteristics of the copolymers are summarized in Table
1.
Figure 1 shows TGA and DSC curves for the polymers. The
polymers showed decomposition temperatures (Td, 5 wt % loss)
from 385 to 404 °C. These high decomposition temperatures
indicate that the introduction of anthracene or TPA as spiro-
structures does not reduce the thermal stability of the polymers.
Moreover, polymers with higher TPA contents showed a higher
main decomposition temperature than that of polymers with
lower TPA contents. The polymers with high TPA contents not
only showed higher Td values but also higher glass transition
temperatures (Tg), except the homopolymer PSAF16. We
Figure 1. TGA and DSC curves for PSAF16 and copolymers.
attribute this phenomenon to the reduced crystallinity of linear
long alkyl chains of the homopolymer. Addition of small portion
of comonomer can disturb the crystallization of side chains.
Although DSC curves of PSAF-T7 and PSAF16 are not clear
to determine Tg, their transition ranges are higher than that of
conventional dialkyl-substituted PFs. The Tg for dihexyl-
substituted PF (PF6) is known to be about 100 °C. Because
light-emitting polymers in OLED are degraded by the Joul heat
generated during device operation, a high Tg is an the absolute
requirement for polymers intended for use in OLED applica-
tions.
Optical Properties of Polymers. UV/vis absorption and
photoluminescence spectra are shown in Figure 2. All PSAF
copolymers showed nearly the same absorption maxima at 400
nm, and exactly the same absorption onset at 413 nm where
the corresponding optical band gap was 3.0 eV. The PL spectra
of PSAF-T7, PSAF-T5, and PSAF-T3 showed emission peaks
similar to PF6. However, the PL spectra for PSAF-T1 and
PSAF16 were quite different. Since PEHSAF, a SAF ho-
mopolymer with ethylhexyl side chains, showed nearly the same
emission peak positions, the red shift can be attributed to the
long alkyl chains of the polymer. PSAF16 contains so long alkyl

6436 Vak et al.
Macromolecules, Vol. 39, No. 19, 2006
Figure 2. Absorption spectra in solution and PL spectra in polymer
films.
Figure 4. EL spectra of PLED with the configuration of ITO/PEDOT:
PSS (40 nm)/emitting polymer (70 nm)/LiF (5 nm)/Ca (30 nm)/silver
(200 nm). Inset shows CIE 1931 color coordinates of the EL spectra.
energy levels of polymers. The polymer with the highest TPA
content, PSAF-T7, showed an HOMO energy level at -5.36
eV, which is nearly the same as the spiro-TPA homopolymer,
PEHSACF. The HOMO energy levels of the polymers increased
with decreasing TPA content. The differences between HOMO
energy levels of PSAF-T5, PSAF-T3, and PSAF-T1 were very
small, but there was significant difference between these of
PSAF-T7 and PSAF-T5. The results were reproducible, and we
conclude that there was no linear relationship between amount
of TPA structure and HOMO energy level. The SAF homopoly-
mer, PSAF16, showed nearly the same HOMO energy level as
that of PF6. From these results, we expected enhanced hole
injection in PSAF copolymers.
Device Characteristics. OLEDs with PSAF16 and its
copolymers were fabricated with the configuration of ITO/
PEDOT:PSS/emitting polymer/LiF/Ca/Ag. The LiF/Ca structure
was adopted as a cathode because it is one of the most efficient
electron injecting cathodes,48 and silver was used as a protecting
layer. Electroluminescence (EL) spectra of devices are shown
in Figure 4. The EL spectra of polymers are nearly the same as
the PL of the polymers. Although there were considerable
differences in EL spectra, all EL spectra were still in the deep
blue region with Commission Internationale de I′Eclairage (CIE)
1931 color coordinates of less than 0.2 for both x and y. The
inset in Figure 3 shows the CIE color coordinates of the
polymers.
Some representative current density-voltage (J-V) and
luminance-voltage (L-V) curves are shown in parts a and b
of Figure 5, respectively. Figure 5a clearly shows the effect of
TPA structure. PSAF copolymers with higher TPA contents
showed higher current density. However, PSAF16 showed a
higher current density than PSAF-T1 and PSAF-T3 in the low
current density regions. This is due to the low injection barrier
of electrons as shown in Figure 6. However, the current densities
of the copolymers became higher than that of PSAF16 at high
injection level due to low mobility of electron. Because the
emission of an OLED depends on both holes and electrons, the
luminance characteristics are not linearly dependent on the TPA
content. However, all copolymer showed better luminescence
characteristics than that of PSAF16 due to the efficient hole
injection and transport properties. Although, copolymers with
higher TPA contents showed a higher current density and
luminescence, the copolymers showed a reverse relationship
between TPA content and external quantum efficiencies. As
Figure 3. Cyclic voltamograms of polymers and ferrocene used as a
reference. Measurements were carried out in 0.1 M Bu4NClO4 in
acetonitrile solution with a scanning rate of 50 mV/s.
chains and such structures are known to induce a greater order
of polymer chains in the solid state and can change the dihedral
angle of the fluorene units. This phenomenon has also been
observed in PFs.44
We measured the PLQE of polymer film on quartz plate in
an integrating sphere following the literature procedure45 and
calculated the values relative to a known material, PEHSAF.35
Since a thick film with an absorbance higher than 1.0 is
recommended46 and there was considerable thickness depen-
dence on PLQE in our experiment when thin films with
absorbance of less than 1.0 were used, we measured PLQE of
samples with an absorbance of 1.0 or higher than 1.0. The
PLQEs were reproducible with about a (5% error range. Since
a SAF polymer, PEHSAF, showed a higher PLQE than
conventional PFs, PSAF16 and PSAF-T1 showed very high
PLQE values. However, polymers with high TPA contents
showed a reduced PLQE.
The energy levels of the PSAF copolymers were characterized
by CV. CV curves of polymers and ferrocene are shown in
Figure 3. The half-wave potential of ferrocene/ferrocenium (Fc/
Fc+) is known to be 4.8 eV below the vacuum level47 and was
used as a calibration reference. Although the optical band-gaps
of PSAF copolymers were similar, there were significant
differences in the highest occupied molecular orbital (HOMO)

Macromolecules, Vol. 39, No. 19, 2006
Polyfluorenes with Spiro-Triphenylamine Structure 6437
Figure 7. External quantum efficiency-current density curves of
PLEDs with the configuration of ITO/PEDOT:PSS (40 nm)/emitting
polymers (70 nm)/LiF (5 nm)/Ca (30 nm)/silver (200 nm).
to the ratio of the number of exciton formation events within
the device to the number of electrons flowing in the external
circuit and the efficiency of the radiative decay of excitons.2
The former is the same as the carrier balance factor, and the
latter is the same as PLQE. Therefore, the external quantum
efficiencies divided by the PLQE value should be used to
consider charge carrier balances. Using this concept, we
conclude that the introduction of a spiro-TPA structure can
enhance device performance with respect to carrier injection,
transport, and balance, the carrier balance is optimized at the
30% TPA content, PSAF-T3, and an excess of TPA structure
can degrade the device performance.
Figure 5. (a) Current density-voltage and (b) luminance-voltage
curves of PLED with the configuration of ITO/PEDOT:PSS (40 nm)/
emitting polymer (70 nm)/LiF (5 nm)/Ca (30 nm)/silver (200 nm).
Summary
We synthesized spiro-PF copolymers with various contents
of spiro-TPA. All polymers showed good optical properties as
blue-emitting materials and enhanced thermal properties with
higher Tg values than conventional PFs. The energy levels of
the polymers were controlled by the amount of spiro-TPA
content from -5.36 to -5.84 for HOMO and from -2.36 to
-2.84 for LUMO. A copolymer with the highest spiro-TPA
content showed the highest current density when the OLED
device was fabricated, and the amount of spiro-TPA content
was optimized in 30% with respect to charge carrier balance.
This study will be useful in molecular engineering of polymers
for OLED, and the spiro-TPA structure will be useful as a
comonomer to modify the energy levels of PF derivatives
without degradation in physical and electrooptical properties.
Experimental Section
Figure 6. Schematic energy levels for electrodes and polymers.
Characterization and Measurements. Materials were charac-
terized by means of H and 13C NMR spectroscopy (JEOL JNM-
1
shown in Figure 6, the HOMO energy level of PSAF-T7 was
modified excessively. Therefore, the polymer showed the highest
current density, much of which would be wasted as a leakage
current. The phenomenon decreased with decreasing TPA
content, and PSAF-T1 showed the highest external quantum
efficiency. However, these results are not reasonable when both
energy barriers are considered for electron and hole injection.
PSAF-T1 has energy barriers of 0.17 eV for an electron and
0.53 eV for a hole, and the energy barriers of PSAF-T5 and
PSAF-T3 are more balanced energy barriers than PSAF-T1. This
problem can be solved by considering the PLQE of the
polymers. The external quantum efficiency is linearly related
LA300WB 300 MHz). Thermal properties, including the glass
transition temperature (Tg), were determined by means of differential
scanning calorimetry (DSC; TA2010) and thermogravimetric
analysis (TGA; TA-2050) at a heating rate of 10 °C/min under
nitrogen. Melting point (mp) was determined by means of DSC.
Elemental analyses were performed by the National Center for Inter-
University Research Facilities, Seoul National University (Elemental
analyzer; CE Instruments Flash EA 1110). Absorption spectra were
measured using a UV/vis spectrophotometer (K-MAC, Spectraview-
2000). The molecular weight of the polymer was determined by
gel permeation chromatography (GPC, Futecs, NS2001) using
tetrahydrofuran (THF) as a solvent and calibrated against polysty-
rene standards. PL and EL spectra were obtained using a CCD

6438 Vak et al.
Macromolecules, Vol. 39, No. 19, 2006
detecter (Princeton Instruments, SPEC-10) with a monochromator
(Acton Research Co. SpectraPro-300i), and excitation sources were
a xenon lamp with monochromator (Acton Research Co. Spectra-
Pro-150) and Keithley 237 Source Measurement Unit, respectively.
PLQEs were measured using the same detection system as PL, He-
Cd laser (series 56, OmNichrome) as excitation source, and
integrating sphere (Labsphere) for the collection of light. The
current-voltage-luminescence characteristics of the devices were
measured by using a Keithley 237 Source Measurement Unit and
an optical power meter (Newport, 1835C) with a calibrated
photodiode (Newport, 818 UV).
Electrochemical Analysis. CV measurements were conducted
in a 0.1 M Bu4NClO4 solution in acetonitrile using a potentiostat
(Eco Chemie, AUTOLAB) at a scan rate of 100 mV/s at room
temperature. An ITO glass, a silver wire, and a platinum wire were
used as the working electrode, reference electrode, and counter
electrode, respectively. The reference electrode was calibrated using
ferrocene. The half-wave potential for the oxidation of ferrocene
was calculated as 4.80 eV from the vacuum energy level. Working
electrodes were prepared by spin-coating using 10 mg/mL polymer
solutions in chlorobenzene.
OLED Fabrication and Characterization. ITO glasses were
cleaned using a washer (Mucasol, Merz) solution in an ultrasonic
bath followed by acetone and methanol cleaning. Surface treatment
was carried out by exposing the ITO glasses to UV-ozone. The
hole injecting layer, PEDOT:PSS (Baytron-P 4083, Bayer), was
spin-coated on the ITO glass with the thickness of 40 nm. The
films were baked at 130 °C for 1 h in air. The films were baked
under nitrogen again for 10 min. 15 mg/mL of PSAF polymer
solutions was spin-coated on the PEDOT:PSS layer with the
thickness of 70 nm and baked under nitrogen for 1 h. 5 nm of LiF,
20 nm of Ca, and 200 nm of Al layer were deposited by thermal
evaporation method under 1 × 10-6 Torr. The active area of a
device was 1 mm2.
reaction mixture, which was then refluxed for 2 h. After cooling
the reaction mixture, the mixture was neutralized by the addition
of 0.1 M HCl and extracted by ether. The organic layer was dried
over MgSO4 and evaporated. Unreacted starting materials were
removed using short liquid column chromatography; the remainder
was charged into a two-neck flask, and 100 mL of acetic acid and
1 mL of concentrated HCl solution were added. The mixture was
refluxed for 6 h, and a white precipitate appeared during this period.
The mixture was cooled to room temperature, and the precipitates
were filtered and dried in a vacuum oven. The product was
recrystallized twice from hot dichloromethane and methanol. The
1
product was a white powder, in 69% yield. H NMR (300 MHz,
CDCl3): δ 0.99 (s, 18H), 1.44 (s, 9H), 6.35 (m, 4H), 7.00 (dd, J )
8.6 Hz, 2.4 Hz, 2H), 7.36 (d, J ) 8.2 Hz, 2H), 7.50 (dd, J ) 8.1
Hz, 1.8, 2H), 7.55 (d, J ) 1.8 Hz, 2H), 7.63 (d, J ) 8.0 Hz), 2H),
7.68 (d, J ) 8.4 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 31.05,
31.42, 33.73, 34.79, 53.37, 57.61, 114.38, 121.26, 122.08, 122.72,
124.09, 124.60, 127.86, 129.26, 130.41, 130.90, 137.24, 138.17,
139.45, 143.01, 151.51, 158.06. Anal. Calcd for C43H43Br2N: C,
70.40; H, 5.91; N, 1.91 Found: C, 70.79; H, 5.91; N, 1.58.
10,10-Bis(hexadecyl)-10H-spiro[anthracene-9,9′-(2′,7′-dibro-
mofluorene)] (4). 10H-Spiro[anthracene-9,9′-(2′,7′-dibromofluo-
rene)] (4.88 g, 10 mmol), an excess of KH, a catalytic amount of
18-crown-6, and 10 mL of THF were placed in a two-neck flask.
1-Bromohexadecane (12.2 g, 40 mmol) was injected, and the
solution was stirred for 5 h at room temperature. The remaining
KH was deactivated by slow addition of methanol. The reaction
mixture was extracted with 300 mL of ether. The solution was dried
over MgSO4 and evaporated. The reaction mixture was purified
by column chromatography using hexane:dichloromethane (0.99:
0.1, Rf ) 0.45). The product was a white powder, in 69% yield. 1H
NMR (300 MHz, CDCl3, ppm): δ 0.87 (m, 10), 1.24 (m, 52), 2.16
(m, 4H), 6.24 (dd, J ) 7.9 Hz, 1.3 Hz, 2H), 6.89 (td, J ) 6.9 Hz,
1.1 Hz, 2H), 7.07 (d, J ) 1.6 Hz, 2H), 7.23 (m, 2H), 7.46 (m, 4H),
7.63 (d, 8.3 Hz, 2H). 13C NMR (100 MHz, CDCl3, ppm): δ 14.04,
22.60, 25.74, 29.27, 29.40, 29.50, 29.51, 29.57, 29.60, 30.03, 31.85,
45.66, 46.72, 57.88, 76.58, 121.26, 122.41, 126.02, 126.27, 127.54,
128.61, 129.15, 130.70, 136.34, 138.25, 139.31, 160.02. Anal. Calcd
for C58H80Br2: C, 74.34; H, 8.61. Found: C, 75.17; H, 8.91.
Polymer Synthesis. 0.69 g of bis(2,5-cyclooctadiene)nickel(0),
0.39 g of dipyridyl, and 0.30 mL of 1,5-cyclooctadiene were placed
on a two-neck flask. 15 mL of anhydrous DMF was injected, and
the solution was then stirred at 80 °C for about 30 min. When the
color of the solution became dark-blue, 1 mmol of mixture of
monomers (3:4 ) 7:3, 5:5, 3:7, 1:9, 0:10) in 60 mL of toluene was
injected to the solution. The solution was stirred at 80 °C for 24 h.
The reaction mixture was poured into the mixture of 250 mL of
methanol and concentrated HCl (methanol:HCl ) 8:2), and the
resulting precipitate was collected. The precipitate was redissolved
in chloroform and reprecipitated using methanol several times.
PSAF16 and PSAF-T1 were pale yellow powders, and the other
polymers were white powders. The yields of polymers were from
Material Synthesis. 10H-Spiro[anthracene-9,9′-(2′,7′-dibromo-
fluorene)] was synthesized using the same way as our previous
report.33 Other starting materials were purchased from Aldrich
Chemical Co. and used without further purification except THF,
which was dried by refluxing over calcium hydride.
Tris(4-tert-butylphenyl)amine (1). A mixture of triphenylamine
(2.45 g, 10 mmol), 2-methylpropan-2-ol (10 mL), and trifluoroacetic
acid (40 mL) was stirred at room temperature for 5 days. During
this period, precipitates appeared. The precipitate was filtered. It
was redissolved in dichloromethane and recrystallized by addition
of hexane. The product was white powder with 71% yield. 1H NMR
(300 MHz, CDCl3): δ 1.30 (s, 27H), 7.01 (d, J ) 8.3 Hz, 6H),
7.23 (d, J ) 8.3 Hz, 6H). 13C NMR (100 MHz, CDCl3): δ 31.37,
34.14, 123.42, 125.93, 145.09, 145.44. Anal. Calcd for C30H38N:
C, 87.11; H, 9.50; N, 3.39 Found: C, 87.00; H, 9.72; N, 2.98.
4-tert-Butyl-N,N-bis(4-tert-butylphenyl)-2-bromobenzen-
amine (2). 1 (4.13 g, 10 mmol) was dissolved in 150 mL of
dichloromethane, and N-bromosuccinimide (NBS) (1.87 g, 10.5
mmol) in 50 mL of N,N-dimethylformamide (DMF) was added
slowly using a dropping funnel under nitrogen. The solution was
stirred at room temperature for 5 h and extracted by dichlo-
romethane. The organic layer was dried over MgSO4, and the
solvents were evaporated. The crude product was recrystallized from
dichloromethane and hexane. The product was a yellowish white
1
40 to 65%. PSAF16. H NMR (300 MHz, CDCl3, ppm): δ 0.83
(m, 6H), 1.16 (m, 56H), 2.18 (br, 4H), 6.24 (m, 2H), 6.74 (m, 2H),
7.14 (m, 6H), 7.43 (br, 4H). Anal. Calcd for C58H80: C, 89.63; H,
10.37. Found: C, 90.41; H, 10.85. PSAF-T1 (copolymer from 90
mol % SAF in the feed): C, 88.99; H, 10.29. PSAF-T3 (copolymer
from 70 mol % SAF in the feed): C, 90.27; H, 10.07; N, 0.16.
PSAF-T5 (copolymer from 50 mol % SAF in the feed): C, 90.09;
H, 9.54; N, 0.70. PSAF-T7 (copolymer from 30 mol % SAF in
the feed): C, 89.30; H, 8.74; N, 0.58.
1
powder with 85% yield. H NMR (300 MHz, CDCl3): δ 1.29 (s,
18H), 1.32 (s, 9H), 6.90 (d, J ) 6.8 Hz, 4H), 7.22 (m, 5H), 7.31
(dd, J ) 8.3, 2.4 Hz, 1H), 7.61 (d, J ) 2.4 Hz, 1H). 13C NMR
(100 MHz, CDCl3): δ 31.19, 31.37, 34.07, 34.51, 121.11, 123.73,
125.76, 125.99, 131.11, 131.34, 142.87, 144.29, 144.29, 144.62,
150.73. Anal. Calcd for C30H37BrN: C, 73.16; H, 7.78; N, 2.84
Found: C, 72.73; H, 7.80; N, 2.43.
Acknowledgment. We thank the Ministry of Science and
Technology, BK21 program, and National Research Laboratory
program of KOSEF for financial support.
2′,7′-Dibromo-10-(4-tert-butylphenyl)-2,7-di-tert-butyl-10H-
spiro(ancridine-9,9′-fluorene) (3). Mg (0.31 g, 13 mmol) was
charged into a two-neck flask and flame-dried. 2 (3.94 g, 8 mmol),
in 10 mL of THF, was added to the flask. The reaction mixture
was refluxed for 1 h under nitrogen and cooled to room temperature.
2,7-Dibromofluorenone (2.46 g, 7 mmol) was rapidly added to the
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