ARTICLE
dioxaborolane, 1,3-bis(diphenylphosphinopropane)-dichloro-
nickel, N,N-dimethylformamide (DMF), xylylenebis(triphenyl-
phosphonium bromide), sodium hydride, and tetrakis(triphe-
nylphosphine)palladium (0) were purchased from Aldrich.
2,5-Dibromo-3-didodecylthiophene (2)
NBS (14 g, 79.2 mmol) was added to a solution of compound
1 (10 g, 39.6 mmol) in tetrahydrofuran (THF; 250 mL) at
0
ꢀC. The reaction mixture was stirred for 24 h and poured
into water. After extracted with methylene chloride, the
organic phase was separated and dried over magnesium
sulfate. The product was obtained after a column chromato-
graphy using hexane as eluent.
Measurements
The 1H NMR and 13C NMR spectra were recorded using a
Bruker AM-200 spectrometer. Fourier transform infrared
spectrometry (FT-IR) spectra were measured on a Bomen
Michelson series FT-IR spectrometer. The melting points
were determined with an Electrothermal Mode 1307 digital
analyzer. The thermal analysis was performed on a TA TGA
2100 thermogravimetric analyzer in a nitrogen atmosphere
at a rate of 20 ꢀC minꢂ1. Differential scanning calorimeter
Yield: 12 g (74%). FT-IR (KBr, cmꢂ1): 2852–2952 (aliphatic
CH2), 1H NMR (300 MHz, CDCl3, ppm): d 6.77 (1H, s), 2.50
(t, 2H), 1.53 (m, 2H), 1.27 (m, 18H), 0.88 (t, 3H).
5-Bromo-3-dodecylthiophene-2-carbaldehyde (3)
Compound 2 (5 g, 12.1 mmol) was mixed with dry THF
(150 mL). This mixture was added with n-butyllithium
(4.8 mL, 2.5 M in hexane, 12.1 mmol) dropwise at ꢂ78 ꢀC
under nitrogen. After the addition was finished, the mixture
was stirred for another 1 h and anhydrous N,N-DMF (0.98 g,
13.4 mmol) was added into solution. The mixture was slowly
warmed to room temperature overnight and poured into 2 N
HCl. The organic layer was extracted with ethyl acetate and
dried over MgSO4. The product was purified by column
chromatography using hexane and ethyl acetate.
was conducted under nitrogen on
a TA instrument
2100 DSC. The sample was heated at 20 ꢀC minꢂ1 from 30
to 250 ꢀC. UV–vis absorption studies were carried out using
Perkin–Elmer LAMBDA-900 UV/VIS/IR spectrophotometer.
The photoluminescence (PL) spectra were measured on a
Perkin–Elmer LS-50 fluorometer utilizing a lock-in amplifier
system with a chopping frequency of 150 Hz. Molecular
weights (Mws) and polydispersities of the copolymers were
determined by gel permeation chromatography (GPC) analy-
sis with polystyrene standard calibration (waters high-
pressure GPC assembly Model M515 pump, u-Styragel col-
umns of HR4, HR4E, and HR5E, with 500 and 100 Å, refrac-
tive index detectors, solvent CHCl3). Cyclic voltammetry (CV)
was performed on an EG and G Parc model 273 Å potentio-
stat/galvanostat system with a three-electrode cell in a
solution of Bu4NClO4 (0.1 M) in acetonitrile at a scan rate of
100 Mv sꢂ1. The polymer films were coated on a square Pt
electrode (0.50 cm2) by dipping the electrode into the corre-
sponding solvents and then drying in air. A Pt wire was used
as the counter electrode, and an Ag/AgNO3 (0.1 M) electrode
was used as the reference electrode.
Yield: 2.71 g (62%). FT-IR (KBr, cmꢂ1): 2852–2959 (aliphatic
CH2), 1747 (C¼¼O), 1H NMR (300 MHz, CDCl3, ppm): d 9.73
(s, 1H), 7.45 (s, 1H), 2.57 (t, 2H), 1.57–1.62 (m, 2H), 1.08–
1.31 (m, 18H), 0.66–0.89 (t, 3H).
1,4-Bis((E)-2-(5-bromo-3-dodecylthiophen-2-yl)
vinyl)benzene (4)
Sodium hydride [0.2 g (8.3 mmol)] was added to the solu-
tion of xylylenebis(triphenyl-phosphonium bromide) (2.98 g,
3.7 mmol) in THF (100 mL). The mixture was stirred at
room temperature for 3 h and then compound 3 (3 g,
8.3 mmol) was added into this solution. After the mixture
was refluxed for 24 h, it was poured into water and
extracted with chloroform following drying with MgSO4. The
solvent was removed via rotary evaporation and the residue
was purified by column chromatography (25% CHCl3 in hex-
ane as eluent). The monomer was recrystallized by ethanol.
Fabrication of the OFET Devices
Top-contacted OFETs were fabricated on a common gate of
highly n-doped silicon with a 300-nm-thick thermally grown
SiO2 dielectric layer. Octadecyltrichlorosilane monolayer was
treated in toluene solution for 2 h. Films of organic semi-
conductor were obtained using chlorobenzene solvent. Gold
source and drain electrodes were evaporated on the top of
semiconductor for the thickness of 100 nm. For all measure-
ments, we used channel length (L) of 100 lm and channel
width (W) of 2000 lm. The electrical characteristics of the
fabricated FETs were measured in air using both Keithley
2400 and 236 source/measure units. Field-effect mobilities
were extracted in the saturation regime from the slope of
the source-drain current.
Yield: 0.93 g (32%). MS (EI) m/z: 788 (Mþ). FT-IR (KBr,
cmꢂ1): 3000 (aromatic CAH), 2846–2916 (aliphatic CH2),1H
NMR (300 MHz, CDCl3, ppm): d 7.39 (s, 4H), 7.25–7.10 (d,
2H), 6.78–6.72 (d, 2H), 6.74 (s, 2H), 2.53–2.48 (t, 4H), 1.57–
1.54 (m, 4H), 1.30–1.11 (m, 36H), 0.90–0.85 (m, 6H). 13C
NMR (300 MHz, CDCl3, ppm): 142.7, 142.3, 136.2, 127.8,
127.0, 126.6, 121.3, 108.1, 77.4, 76.9, 76.5, 31.9, 29.6, 29.5,
29.5, 29.4, 29.4, 29.3, 29.1, 22.6, 14.0 Anal Calcd. for
C42H60Br2S2:C, 63.96%; H, 7.62% Found: C, 63.90%; H, 7.59%.
Synthesis
3-Dodecylthiophene (1)
2,7-Dibromo-9H-fluorene (5)
Bromine (1.23 mL, 24.06 mmol) was added slowly to a mix-
ture of 9H-fluorene (2 g, 12.03 mmol), iodine, and dichloro-
methane (40 mL) over 30 min at 0 ꢀC in the dark. The
mixture was stirred at 0 ꢀC for 1 h and then at room tem-
perature for 2 h. An aqueous Na2CO3 solution (10%) and
then water were added to quench the reaction. The organic
phase was separated and the aqueous phase was extracted
3-Dodecylthiophene was synthesized using the procedure
reported elsewhere10 with yield of 70%; bp ¼ 104 ꢀC/
1 mmHg.
1H NMR (300 MHz, CDCl3, ppm): d 7.26 (s, 1H), 6.95 (m.
2H), 2.65 (t, 2H), 1.63–1.67 (m, 2H), 1.30–1.34 (m, 18H),
0.92 (t, 3H).
SYNTHESIS AND CHARACTERIZATION OF PEFTVB AND POFTVB, LEE ET AL.
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