Macromolecules, Vol. 37, No. 16, 2004
Hyperbranched Blue-Light-Emitting Copolymers 5969
diethyl ether. The combined organic solution was washed with
water until the aqueous layer became neutral. The organic
solution was dried (MgSO4). The product was separated by
silica gel column chromatography (hexanes) and was obtained
as a light yellow oil (3.1 g, 66.1%). Anal. Cacld for C33H50: C,
88.7; H, 11.3. Found: C, 89.0; H, 11.5. 1H NMR (CDCl3): 0.77
(t, J ) 6.8 Hz, 6 H, 2CH3), 0.94 (t, J ) 7.6 Hz, 6 H, 2CH3′),
1.04-1.14 (m, 16 H), 1.36 (q, J ) 7.6 Hz, 4 H, 2CH2), 1.63 (t,
J ) 8.0 Hz, 4H, 2CH2), 1.89-1.93 (m, 4H, 2CH2), 2.68 (t, J )
7.6 Hz, 4H, 2CH2), 7.10 (s, 2H, aromatic-H), 7.11 (d, J ) 8.0
Hz, 2H), 7.54 (d, J ) 8.0 Hz, 2H, aromatic-H). 13C NMR
(CDCl3): δ 14.3, 22.6, 22.9, 24.0, 30.0, 31.8, 34.4, 36.3, 40.7,
55.0, 119.3, 123.2, 127.1, 139.2, 141.8, 151.1. MS (EI), m/e:
446.3 (M+, 100%).
A Gen er a l P r oced u r e for th e Syn th esis of P olym er s
5-8. Tetrabromoarylmethane/silane (0.5 g), 9,9-dihexylfluo-
rene-2,7-diboronic acid (2.0 equiv), and [Pd(PPh3)4] (1 mol %)
were dissolved in THF (112.5 mL) and 2 M K2CO3 (aq, 75 mL).
The reaction mixture was degassed by bubbling with N2 and
then was heated at 65 °C (oil-bath temperature) for 4 h (5-7)
or 8 h (8) under N2. Upon completion, the THF layer was
separated. After removal of THF, the solid was washed with
water and ethanol. The dried product was washed with acetone
(5 and 6) or ethanol (7 and 8) using a Soxhlet apparatus for
24 h to remove the catalyst residues and oligomers. The
polymers tended to form stable inclusion complexes with
ethanol or acetone. Heating of the polymers at 120 °C under
vacuum overnight removed the solvents. The products were
isolated as light yellow powders.
nonaggregating property in the solid state would make
the present polymers a novel class of blue emitters.
Exp er im en ta l Section
The starting materials 2,7-dibromo-9,9-dihexylfluorene and
9,9-dihexylfluorene-2,7-bis(trimethylene boronate) were pre-
pared according to a literature method.15,16 Unless stated
otherwise, all reagents and solvents were of commercial grade
and used as received. All reactions were performed under a
purified nitrogen atmosphere. Tetrahydrofuran (THF) was
distilled over CaH2 before use.
The 1H NMR spectra were recorded at 25 °C on a Bruker
AVANCE 400 spectrometer. Mass spectra were recorded on a
Finnigan/MAT TSQ 7000 or an ABI Voyager STR spectrom-
eter. UV-vis spectra were measured with a UV-vis spectrom-
eter (Shimadzu, UV-2501 PC) at 20 °C. Fluorescence spectra
were recorded on a LS50B luminescence spectrometer (Perkin-
Elmer) at 20 °C. Melting points and glass transition temper-
atures were determined by differential scanning calorimetry
(DSC) experiments using a TA 2920 modulated DSC instru-
ment with a ramp speed of 10 °C/min. Thermogravimetric
analyses (TGA) were conducted on a Perkin-Elmer thermo-
gravimetric analyzer TGA 7 under a heating rate of 20 °C/
min and a nitrogen flow rate of 20 cm3/min. The photolumi-
nescent quantum yields (ΦPL) of the polymers in THF were
determined using a solution of quinine sulfate as a standard
(ca. 1 × 10-5 M in 0.1 M H2SO4, having a quantum yield of
55%). The ΦPL values of films were determined using 9,10-
diphenylanthracene as a standard (dispersed in PMMA films
with a concentration lower than 1 × 10-3 M and a quantum
efficiency of 83%). WAXS measurements were conducted using
Bruker X-ray diffractometer using Cu KR (λ ) 1.541 Å)
radiation. The X-ray tube was operated at 40 kV and 40 mA.
Elemental analyses were performed by the Elemental Analysis
Laboratory of the Department of Chemistry at the National
University of Singapore.
P olym er 5. A light yellow solid. Anal. Calcd for (C75H80)n:
1
C, 91.8%; H, 8.2%. Found: C, 91.2%; H, 8.2%. H NMR (400
MHz, CDCl3): δ 0.74 (br 12H), 1.03 (br 32 H), 1.99 (br, 8H),
7.10 (d, J ) 8.4 Hz, 2H), 7.20 (d, J ) 8.4 Hz, 2H), 7.32 (d, J )
7.8 Hz, 4H), 7.42 (d, J ) 8.4 Hz, 4H), 7.52-7.76 (m, 16 H). 13
C
NMR (100 MHz, THF-d8): δ 14.9, 24.0, 31.3, 33.1, 42.0, 55.6,
63.0, 121.1, 121.4, 121.8, 122.5, 124.2, 127.2, 127.6, 128.3,
132.4, 133.0, 134.2, 140.6, 141.0, 147.5, 152.3, 153.1.
A Gen er a l P r oced u r e for th e Syn th esis of Si(p-Ar Br )4.
2,4-Dibromobenzene or 4,4′-dibromobiphenyl (10 g) and mag-
nesium turnings (1.05 equiv of BrArBr) were dissolved in 150
mL of THF. The Grignard reaction was initiated by addition
of I2. The reaction mixture was first stirred at room temper-
ature for 2 h and then was heated at 65 °C overnight to give
a brown solution of the Grignard reagent. To a solution of Si-
(OEt)4 (0.25 equiv of BrArBr) in 50 mL of THF was added the
Grignard agent at room temperature. The reaction mixture
was stirred at room temperature for 16 h and then refluxed
for 4 h. Upon completion, 100 mL of 1 N HCl was added slowly
into the reaction mixture. The organic layer was isolated, and
the aqueous layer was extracted with dichloromethane (2 ×
150 mL). The combined organic solution was washed with
brine and dried (MgSO4). Filtration through Celite gives a clear
yellow solution. The product was purified by silica gel column
chromatography (hexanes/chloroform 2:1).
P olym er 6.
A light yellow solid. Anal. Calcd for
(C74H80Si)n: C, 89.1%; H, 8.1%. Found: C, 88.9%; H, 8.1%. 1H
NMR (THF-d8): δ 0.67 (br, 12H), 0.97 (br, 32 H), 2.03 (br, 8H),
7.10-7.82 (m, 28 H). 13C NMR (100 MHz, THF-d8): δ 14.9,
24.0, 31.3, 33.0, 41.8, 56.0, 121.2, 121.6, 122.4, 122.8, 123.2,
126.7, 127.4, 127.7, 131.8, 134.5, 137.0, 138.2, 142.5, 152.5,
153.0.
P olym er s 7 a n d 8. Light yellow solids. Anal. Calcd for
(C98H96Si)n: C, 90.4%; H, 7.4%. Found: C, 90.0%; H, 7.4%. 1H
NMR (CDCl3): δ 0.77 (br, 12H), 1.09 (br, 32 H), 2.08 (br, 8H),
7.30 (d, J ) 8.4 Hz, 2H), 7.36 (d, J ) 8.4 Hz, 2H), 7.52 (d, J )
8.4 Hz, 2H), 7.59-7.80 (m, 38 H). 13C NMR (CDCl3): δ 14.3,
22.9, 24.1, 30.1, 31.8, 40.8, 55.7, 120.1, 120.5, 121.8, 123.2,
126.3, 126.5, 127.1, 127.4, 127.8, 128.0, 129.0, 129.2, 132.3,
135.3, 139.9, 140.5, 141.1, 150.9, 151.8, 152.1.
EL Device F a br ica tion . For the fabrication of the devices,
glass substrates coated with indium-tin oxide (ITO) with a
sheet resistance of 30 Ω γ-1 (CSG Co. Ltd.) were cleaned
sequentially in ultrasonic baths of aqueous ionic detergent,
acetone, and anhydrous ethanol. A thin film layer of PEDOT
(80 nm) and polymer 8 (50 nm) (from a 15 mg/mL solution of
the polymers in THF solution) was spin-coated on the ITO
surface at 1000 rpm for 60 s, after which a thin layer of LiF
(0.5 nm)/Ca(20 nm) was deposited on the polymer film by
thermal evaporation under a vacuum of 10-6 Torr. The active
area of the device was about 4.0 mm2. The applied dc bias
voltages for EL devices were in a forward direction (ITO,
positive; LiF/Ca/Ag, negative). The current-voltage charac-
teristics were measured on a voltmeter and an amperometer,
respectively. The EL efficiency and brightness measurements
were carried out with a calibrated silicon photodiode. All the
measurements of the EL devices were carried out in air at
room temperature.
Tetr a (4-br om op h en yl)sila n e (2). A colorless solid 4.3 g
(62%). The physical and spectroscopic data were identical to
those reported in the literature.12
Tetr a (4-br om obip h en yl)sila n e (3). A white solid 3.5 g
(51%); mp > 300 °C. Anal. Cacld for C48H32Br4Si: C, 60.3; H,
3.4; Br, 33.4. Found: C, 60.5; H, 3.2; Br, 33.0. 1H NMR
(CDCl3): δ 7.41 (d, 4H, 3J HH ) 8.4 Hz), 7.46 (d, 4H, 3J HH ) 8.8
3
Hz), 7.57 (d, 16H, J HH ) 8.4 Hz). 13C NMR (CDCl3): δ 127.3,
128.0, 128.8, 129.1, 129.2, 132.2, 132.4, 139.2. MALDI-TOF
MS, m/e: 956.67 (M+, 100%).
Syn th esis of 2,7-Dibu tyl-9,9-d ih exylflu or en e (4). 9,9-
Dihexyl-2,7-dibromofluorene (5 g, 10 mmol) was dissolved in
dry THF (100 mL) and cooled to -20 °C. To the solution was
added n-BuLi (15 mL, 24 mmol) dropwise. The reaction
mixture was stirred at -20 °C for 2 h. To the above solution
was then added B(OMe)3 (3.2 mL, 28 mmol) through a springe
in one portion. The reaction mixture was stirred at -20 °C
for 3 h and warmed to room temperature and continued to
stir overnight. After the mixture was cooled to 0 °C, it was
quenched with 20 mL of 1 N HCl. The organic layer was
isolated, and the aqueous layer was diluted and extracted with
Ack n ow led gm en t. We are grateful to the Agency
for Science, Technology and Research (A*Star), Singa-
pore, for its financial support.