Chemistry of Materials
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3.38 mmol), and cyclooctadiene (0.53 g, 3.38 mmol) were added to 70
mL of anhydrous dimethyl formamide (DMF), and the mixture was
stirred at 60 °C for about 30 min. The compound 6a (3.0 g, 4.51
mmol) was then added to the reaction mixture, which was then stirred
at 90 °C for 48 h. After the reaction, a mixture solution of ammonium
hydroxide and methanol (mixing ratio = 1:2, about 1.2 L) was added
to the reaction solution and stirred for about 12 h. Subsequently, the
product solid obtained by filtering was dissolved in chloroform and
then reprecipitated several times in methanol. After drying for about
mmol) of 2-tributylstannylthiophene as an end-capper. The polymer
was poured into 300 mL of dilute aqueous HCl/MeOH (1/2) solution
and then filtered to produce a dark reddish solid. The obtained
polymer solid was dissolved in CHCl3 and was washed with a dilute
aqueous HCl solution, NH4OH (aq), and distilled water sequentially.
The crude polymer was precipitated into MeOH and was fractionated
by Soxhlet extraction with methanol, acetone, dichloromethane, and
chloroform. The chloroform fraction was characterized and used.
Removal of the chloroform solvent was followed by drying for 2 days
in vacuum and yielded a dark red solid (0.23 g, yield = 53%). GPC
(100 °C in trichlorobenzene, polystyrene standards): Mn = 16,289,
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24 h in vacuum, a compound was obtained; 7a (yield = 94.3%). H
NMR (300 MHz, CDCl3, δ): 7.44 (d, J = 3.9 Hz, 2H), 7.22 (d, J = 5.2
Hz, 2H), 7.11 (d, J = 3.9 Hz, 2H), 6.96 (d, J = 5.2 Hz, 2H), 2.82 (t, J =
7.7 Hz, 4H), 2.68 (t, J = 7.7 Hz, 4H), 1.72−1.61 (m, 8H), 1.26−1.23
(m, 72H), 0.90−0.84 (m, 12H).
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PDI = 2.07; H NMR (300 MHz, CDCl3, δ): 7.09 (m, thiophene-H),
7.02 (m, thiophene-H), 6.90 (m, thiophene-H), 2.92 (broad, alkyl-H),
2.81 (broad, alkyl-H), 2.71 (broad, alkyl-H), 1.72 (broad, alkyl-H),
1.26 (broad, alkyl-H), 0.87 (m, methyl-H); Elemental Analysis:
calculated for C78H112N2S8: C, 70.21; H, 8.46; N, 2.10; S, 19.23.
Compound 7b. This compound was obtained according to the
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procedure described above for 7a. H NMR (300 MHz, CDCl3, δ):
7.20 (d, J = 5.4 Hz, 2H), 6.98 (s, 2H), 6.95 (d, J = 5.4 Hz, 2H), 2.81 (t,
J = 7.8 Hz, 4H), 2.70 (t, J = 7.8 Hz, 4H), 1.73−1.61 (m, 12H), 1.44−
1.27 (m, 60H), 0.89−0.83 (m, 18H).
found: C, 70.28; H, 8.19; N, 1.99; S, 19.11; UV−vis spectrum: λmax
=
490 nm (solution, in CHCl3), λmax = 513 nm (film state from
chlorobenzene solution).
Compound 7c. This compound was obtained according to the
Compound 10. (PHTBTz-C8): The same procedure as for 9 was
applied for this synthesis, starting with a mixture of compound 8b
(0.60 g, 2.40 mmol) and 2,5-Bis(trimethylstannyl)thiophene (0.79 g,
2.40 mmol). GPC (100 °C in trichlorobenzene, polystyrene
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procedure described above for 7a H NMR (300 MHz, CDCl3, δ):
7.19 (d, J = 5.4 Hz, 2H), 6.98 (s, 2H), 6.95 (d, J = 5.1 Hz, 2H), 2.91 (t,
J = 7.7 Hz, 4H), 2.82 (t, J = 7.8 Hz, 4H), 2.70 (t, J = 7.7 Hz, 4H),
1.73−1.64 (m, 12H), 1.41−1.23 (m, 108H), 0.87−0.84 (m, 18H).
Compound 8a. The obtained compound 7a (2.49g, 2.13 mmol)
was reacted with NBS (0.79 g, 4.46 mmol) in a chloroform solution
(120 mL) with acetic acid. The mixture was stirred at room
temperature overnight. The solvent was removed by heating under
vacuum, and the residue was dissolved in chloroform and washed with
brine. The collected organic layer was dried over sodium sulfate, and
the organic solvent was removed by rotary evaporation. The residue
was purified by silica column purification (n-hexane:chloroform = 5:1),
and the collected compound was purified by recrystallization in
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standards): Mn = 14,204, PDI = 2.14; H NMR (300 MHz, CDCl3,
δ): 7.09 (s, Ar−H), 7.02 (d, Ar−H), 2.92 (broad, alkyl-H), 2.82
(broad, alkyl-H), 2.71 (broad, alkyl-H), 1.75 (broad, alkyl-H), 1.43−
1.24 (broad, alkyl-H), 0.88−0.84 (m, methyl-H); Elemental Analysis:
calculated for C78H112N2S8: C, 70.21; H, 8.46; N, 2.10; S, 19.23. found:
C, 70.19; H, 7.98; N, 2.01; S, 19.98; UV−vis spectrum: λmax = 475 nm
(solution, in CHCl3), λmax = 540 and 586 nm (film state from
chlorobenzene solution).
Compound 11. (PHTBTz-C12): The same procedure as for 9 was
applied for this synthesis, starting with a mixture of compound 8c (0.6
g, 2.40 mmol) and 2,5-Bis(trimethylstannyl)thiophene (0.789 g, 2.40
mmol). GPC (100 °C in trichlorobenzene, polystyrene standards):
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ethanol to yield 8a as a reddish-orange powder in yield = 84.0%. H
NMR (300 MHz, CDCl3, δ): 7.42 (d, J = 3.9 Hz, 2H), 7.02 (d, J = 3.9
Hz, 2H), 6.92 (s, 2H), 2.75 (t, J = 7.7 Hz, 4H), 2.68 (t, J = 7.6 Hz,
4H), 1.73−1.60 (m, 8H), 1.25−1.23 (m, 72H), 0.90−0.84 (m, 12H);
13C NMR (125 MHz, CDCl3, δ): 159.82, 148.83, 141.06, 137.42,
136.85, 134.30, 132.83, 131.49, 129.66, 126.71, 126.39, 119.23, 111.27,
91.08, 38.05, 31.92, 29.67, 29.64, 29.55, 29.42, 29.37, 22.69, 14.13;
MALDI TOF MS: 1326.50 [M+H]; calculated exact mass: 1326.65;
Elemental Analysis: calculated for C70H106Br2N2S6: C, 63.32; H, 8.05;
N, 2.11; S, 14.49. found: C, 63.00; H, 7.70; N, 1.91; S, 15.01.
Compound 8b. This compound was obtained according to the
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Mn = 15,058, PDI = 1.85; H NMR (300 MHz, CDCl3, δ): 7.09 (s,
Ar−H), 7.02 (d, Ar−H), 2.91 (broad, alkyl-H), 2.82 (broad, alkyl-H),
2.71 (broad, alkyl-H), 1.74−1.61 (broad, alkyl-H), 1.43−1.24 (broad,
alkyl-H), 0.89−0.85 (m, methyl-H); Elemental Analysis: calculated for
C102H160N2S8: C, 73.32; H, 9.65; N, 1.68; S, 15.35. found: C, 73.28; H,
9.09; N, 1.60; S, 15.15; UV−vis spectrum: λmax = 474 nm (solution, in
CHCl3), λmax = 545 and 590 nm (film state from chlorobenzene
solution).
Sample Preparation for Charaterization. In order to confirm
the nanomorphology and molecular orientation, PHTBTz-H, -C8, and
-C12 thin films were spin-coated using 1 wt % solutions in
chlorobenzene on ODTS-treated SiO2 substrates and annealed at
180 °C, 160 °C, and 140 °C, respectively, for 1 h in a N2 atmosphere.
Device Fabrication and Electrical Characterization. The
electrical properties of PHTBTz series were evaluated using coplanar
structured OFETs. The PHTBTz’s based OFETs were fabricated
using spin-coating and inkjet printing. For the spin-coated film based
OFET devices, heavily doped silicon wafers were used, and steel
shadow masks were used for the formation of Au source/drain
electrode patterns. Then, the polymer thin films were spun from a 1.0
wt % chlorobenzene solution of the polymers. On the other hand, for
the fabrication of inkjet-printed OFETs, molybdenum (Mo) was
sputter-deposited onto glass substrates as the first step. The deposited
Mo was then patterned to form a gate electrode by photolithography.
Next, a 300 nm thick silicon dioxide (SiO2, capacitance Ci = 10 nF
cm−2) was deposited by plasma enhanced chemical vapor deposition
(PECVD) as the gate dielectric. Source-drain electrodes (Au: thickness
∼70 nm) were next deposited by e-beam evaporation and patterned
again by photolithography, resulting in a channel width of 120 μm and
length of 12 μm. The surface of the gate dielectric was then treated
with self-assembled monolayers (SAM) of octadecyltrichlorosilane
(ODTS) (purchased from Aldrich). Polymer semiconductors were
dissolved in tetrahydronaphthalene (THN) to a concentration of 0.2
wt % and then printed onto the already patterned source-drain
electrodes using a Dimatix inkjet printer. Finally, PHTBTz-H, -C8, and
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procedure described above for 8a. H NMR (300 MHz, CDCl3, δ):
6.91 (d, J = 2.1 Hz, 4H), 2.89 (t, J = 7.8 Hz, 4H), 2.75 (t, J = 7.8 Hz,
4H), 2.69 (t, J = 7.8 Hz, 4H), 1.74−1.60 (m, 12H), 1.43−1.27 (m,
60H), 0.89−0.83 (m, 18H); 13C NMR (125 MHz, CDCl3, δ): 159.67,
156.90, 142.71, 140.87, 135.65, 132.83, 131.76, 129.28, 119.42, 110.97,
31.87, 30.43, 30.09, 29.83, 29.73, 29.65, 29.47, 29.43, 29.38, 29.28,
29.23, 22.67, 14.10; MALDI TOF MS: 1326.50 [M+H]; calculated
exact mass: 1326.66; Elemental Analysis: calculated for
C70H106Br2N2S6: C, 63.32; H, 8.05; N, 2.11; S, 14.49. found: C,
63.49; H, 7.83; N, 2.03; S, 14.26.
Compound 8c. This compound was obtained according to the
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procedure described above for 8a. H NMR (300 MHz, CDCl3, δ):
6.91 (d, J = 1.8 Hz, 4H), 2.89 (t, J = 7.8 Hz, 4H), 2.75 (t, J = 7.8 Hz,
4H), 2.69 (t, J = 7.8 Hz, 4H), 1.73−1.60 (m, 12H), 1.43−1.23 (m,
108H), 0.89−0.83 (m, 18H); 13C NMR (125 MHz, CDCl3, δ):
159.69, 156.92, 142.75, 140.90, 135.74, 132.84, 131.81, 131.51, 129.29,
119.45, 111.00, 31.93, 30.44, 30.11, 29.66, 29.49, 29.37, 22.69, 14.10;
MALDI TOF MS: 1663.38 [M+H]; calculated exact mass: 1660.88;
Elemental Analysis: calculated for C94H154Br2N2S6: C, 67.83; H, 9.33;
N, 1.68; S, 11.56. found: C, 67.85; H, 9.08; N, 1.59; S, 11.20.
Compound 9. (PHTBTz-H): 2,5-Bis(trimethylstannyl)thiophene
(0.13 g, 0.26 mmol) and compound 8a (0.4 g, 0.38 mmol) were
dissolved in a mixture of anhydrous DMF/THF in a N2 atmosphere.
Subsequently, Pd(PPh3)4 (43.0 mg, 10 mol %) was added to the
mixture and reacted at 85 °C for 60 min, and then the mixture was
stirred for 2 h after the addition of an excess amount (1.41 g, 3.76
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dx.doi.org/10.1021/cm400592b | Chem. Mater. 2013, 25, 1927−1934