2,5-Dioctyloxylterephthalic dihydrazide (I). 7.2 g (0.015 mol)
of diethyl 2,5-dioctyloxyterephthalate was added to a solution
of 10 ml of hydrazine monohydrate (99%) in 60 ml of
CH OH. The reaction mixture was reÑuxed for 24 h. Then the
3
mixture was cooled and Ðltered to give a white precipitate.
The precipitate was recrystallized from ethanol and dried in
vacuum at 60 ¡C to yield 6.4 g (95%) white crystals. Mp 98.0È
99.0 ¡C. MS: m/z 450. 1H NMR (CDCl ) d 9.19 (broad, 2 H,
3
NH), d 7.84 (s, 2 H), 4.19È4.16 (t, J \ 6.7, 4 H), 4.18È4.16 (d, 4
H, NH ), 1.92È1.82 (m, 4 H), 1.48È1.28 (m, 20 H), 0.88È0.86 (t,
2
J \ 6.8, 6 H). 13C NMR (CDCl ) d 165.24, 150.70, 122.97,
3
115.66, 69.80, 31.61, 29.08, 29.02, 28.97, 25.88, 22.50, 13.95.
Analysis calculated for C
12.43. Found: C, 63.78; H, 9.29; N, 12.22.
H
N O : C, 63.97; H, 9.39; N,
24 42
4 4
Scheme 1 Chemical structure for PCOPO.
N-(2º-ethylhexyl)carbazole.15 To the mixture of 16.7 g (0.1
mol) of carbazole dissolved in 120 ml of ethanol was added
11.2 g (0.2 mol) of potassium hydroxide. The mixture was
reÑuxed for 0.5 h, and then 38.6 g (0.2 mol) of 2-ethylhexyl
bromide was added dropwise over a period of 1 h. The
mixture was further reÑuxed for 6 h. After cooling to room
temperature, the mixture was poured into water (250 ml) and
extracted with ether three times (60 ml each), then dried with
anhydrous magnesium sulfate. The solvents were removed by
rotary evaporation and the residue was distilled to remove the
excess 2-ethylhexyl bromide. The residue was puriÐed by
silica-gel column chromatography using hexane : ethyl acetate
(10 : 1) as the eluent. The yield is 81%. MS: m/z 279. 1H NMR
Experimental
Measurements
NMR spectra were collected on a Bruker ACF 300 spectro-
meter with chloroform-d as solvent and tetramethylsilane as
internal standard. FT-IR spectra were recorded on a Bio-Rad
FTS 165 spectrometer by dispersing samples in KBr disks.
UV-Vis and Ñuorescence spectra were obtained on a Shi-
madzu UV 3101PC UV-Vis-NIR spectrophotometer and a
Perkin Elmer LS 50B luminescence spectrometer with a xenon
lamp as light source, respectively. Elemental analyses were
performed on a Perkin-Elmer 240C elemental analyzer for C,
H, N, and S determinations. Cyclic voltammetry was per-
formed using an EG&G Model 273A potentiostat/galvanostat
under argon atmosphere. All potentials were measured against
a Ag/Ag` (0.1 M in acetonitrile) electrode (0.34 V vs. SCE)
and all of the experimental values in this report were corrected
with respect to SCE. Gel permeation chromatography (GPC)
analysis was conducted with a Perkin Elmer Model 200
HPLC system equipped with PhenogelTM MXL and MXM
columns using polystyrene as standard and THF as eluent.
(CDCl ) d 8.21È8.18 (m, 2 H), 7.57È7.34 (m, 4 H), 7.31È7.29 (m,
3
2 H), 4.23È4.20 (d, J \ 7.2, 2 H), 2.18È2.14 (m, 1 H), 1.51È1.33
(m, 8 H), 1.02È0.94 (m, 6 H). 13C NMR (CDCl ) d 141.07,
3
125.65, 122.97, 120.39, 118.82, 109.08, 47.42, 39.49, 31.15, 28.95,
24.55, 23.20, 14.18, 11.03. Analysis calculated for C
86.02; H, 8.96; N, 5.02. Found: C, 85.79; H, 9.09; N, 5.27.
H
N: C,
20 25
3,6-Bis(N,N-dimethylcarbamoyl)-9-(2º-ethylhexyl)carbazole.16
To a stirred mixture of 9.6 g (0.070 mol) of aluminum chloride
and 30 ml of ethylene chloride under nitrogen was added a
solution of 9.8 g (0.035 mol) of N-(2@-ethylhexyl)carbazole dis-
solved in 30 ml of ethylene chloride. Then a solution of 7.5 g
(0.070 mol) of N,N-dimethylcarbamoyl chloride in 30 ml of
ethylene chloride was added dropwise over 20 min. The
mixture was heated under reÑux for 24 h under nitrogen, then
cooled and poured into 50 ml water and extracted with chlo-
roform three times (20 ml each). The combined organic layer
was washed with water, until the washings were neutral to
litmus paper, and dried over magnesium sulfate. The solvent
was evaporated under reduced pressure and the residue was
puriÐed by silica-gel column chromatography using ethyl
acetate as the eluent. Yield 73%. Mp 55.0È57.0 ¡C. MS: m/z
LED device fabrication
In the fabrication of single layer LED devices, indium tin
oxide-coated (ITO) glass with a resistivity of 250 )~1 was
used as substrate. A uniform Ðlm (thickness about 1200 A) of
the polymer was obtained by spin-coating from the polymer
solution dissolved in triÑuoroacetic acid (TFA)ÈCHCl at a
rate of 5000 rpm for 2 min. The Ðlm was dried in a vacuum
oven at 30 ¡C before the device fabrication. Aluminum was
vapor-deposited (JEOL-400 Vacuum Evaporator) through a
mask as the top electrode at a pressure of around 3 ] 10~4
Torr, yielding a 1200 A layer (Thickness Monitor Model TM-
200R, Maxtek Inc.). An active area of the LED device is about
1 mm2. Electrical contacts were Ðxed using a conductive
epoxy 14G adhesive. Sample processing and handling was
done under ambient atmosphere. Electrical and optical char-
acterizations were also carried out under ambient atmosphere.
CurrentÈvoltage (IÈV ) characteristics were measured with a
Keithley 238 High Current Source Measure unit. Voltages are
given as the potential of the ITO electrode with the aluminum
contact grounded; forward bias denotes ITO contact positive.
3
421. 1H NMR (CDCl ) d 8.18È8.17 (m, 2 H), 7.60È7.56 (m, 2
3
H), 7.40È7.38 (m, 2 H), 4.17È4.16 (d, J \ 7.2, 2 H), 3.12 (s, 12
H), 1.85È1.80 (m, 1 H), 1.37È1.20 (m, 8 H), 0.93È0.81 (m, 6
H). 13C NMR (CDCl ) d 172.32, 141.80, 127.01, 125.63,
3
122.10, 120.00, 108.86, 47.57, 39.24, 30.86, 28.66, 24.26, 22.86,
13.89, 13.85, 10.76. Analysis calculated for C
74.07; H, 8.37; N, 9.97. Found: C, 74.05; H, 8.35; N, 9.33.
H
N O : C,
26 35
3
2
N-(2º-ethylhexyl)carbazole-3,6-dicarboxylic acid.16 A mixture
of 6.0 g (0.014 mol) of 3,6-bis(N,N-dimethylcarbamoyl)-9-(2@-
ethylhexyl)carbazole and 40 ml of 20% ethanolic potassium
hydroxide was reÑuxed for 6 h. The solvent was evaporated
and the residue was poured into water, then the solution was
acidiÐed with concentrated hydrochloric acid. The precipitate
was collected by Ðltration and washed with water. Rec-
rystallization from ethanol gave the white powder product.
Yield 70%. Mp 310È313 ¡C. MS: m/z 367. 1H NMR (DMSO-
Materials
Triethylamine was purchased from Aldrich and was re-
distilled prior to use. Carbazole, 2-ethylhexyl bromide, alu-
minum chloride, N,N-dimethylcarbamoyl chloride, ethylene
chloride, thionyl chloride were used as received (Fluka or
Aldrich chemicals).
d ) d 12.66 (s, br, 2 H), 8.87 (s, 2 H), 8.11È8.09 (d, J \ 8.9, 2 H),
6
The detailed synthetic route to the target polymer is
depicted in Scheme 2.
7.70È7.67 (d, J \ 8.7, 2 H), 4.35È4.32 (d, J \ 7.4, 2 H), 2.01È
1.97 (m, 1 H), 1.35È1.14 (m, 8 H), 0.86È0.72 (m, 6 H). 13C
3124
Phys. Chem. Chem. Phys., 1999, 1, 3123È3127