Macromolecules
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Compound 2. In a 250 mL round-bottom flask, compound 1 (5 g,
27 mmol) was dissolved in 50 mL of chloroform and 50 mL of
trifluoroacetic acid. Sodium perborate monohydrate (6.4 g, 63 mmol)
was added into the solution in one portion, and the mixture was stirred
at room temperature (25 °C) for 45 min. Then, 200 mL of water and
200 mL of chloroform were added to extract the organic part. The
solvent was removed by an evaporator. The compound was purified by
silica gel chromatography using a dichloromethane (DCM) and
hexane mixture (1:1, v:v) as the eluent to obtain a white solid (1.6 g,
yield 30%). 1H NMR (CDCl3, 400 MHz): 7.66 (d, 1H), 7.47 (d, 1H),
7.27 (d, 1H), 7.11 (d, 1H).
mL of ice−water to afford a large amount of white precipitate. The
precipitate was filtered and collected and then purified by silica gel
chromatography using a hexane and ethyl acetate mixture (4:1, v:v) as
the eluent to obtain a white solid. The white solid was recrystallized in
methanol to afford a white needle-like crystal (1.9 g, yield 40%). 19F
NMR (CDCl3, 400 MHz): −118.9 (s, 2F). GC-MS: 330.0 [M+]
(purity >99%).
Polymerization for PDTP−DFBT. M1 (0.431g, 0.410 mmol) and
M2 (0.131g, 0.397 mmol) were dissolved into 20 mL of toluene in a
flask protected by argon. The solution was flushed with argon for 10
min, and then 7 mg of Pd2(dba)3 and 14 mg of P(o-tol)3 were added
into the flask. The solution was flushed with argon again for another
10 min. The oil bath was heated to 100 °C gradually, and the reaction
mixture was stirred for 4 h at 100 °C under an argon atmosphere. 400
mg of bromobenzene was added, and the mixture was stirred for 4 h.
Then, the mixture was cooled down to room temperature, and the
polymer was precipitated in 100 mL of methanol and the precipitated
solid was collected. Low molecular weight portion was removed by
Soxhlet extraction using acetone (6 h) and hexane (12 h). The
polymer which remained in the extraction thimble was dissolved into
50 mL of chlorobenzene, to which was added 2 g of sodium
diethyldithiocarbamate and 40 mL of water followed by stirring at 80
°C for 6 h. The aqueous phase was removed, and the organic phase
was washed with 50 mL of water twice and then with 50 mL of 3 wt %
acetic acid aqueous solution twice, followed by two more washings
with 5% potassium fluoride aqueous solution and two more with
water. The polymer was further purified by silica gel chromatography
using chlorobenzene as eluent. Then the polymer was precipitated in
100 mL of methanol and obtained as dark purple solid; yield ∼70%.
The polymer can be dissolved chlorobenzene or dichlorobenzene, etc.
1H NMR (400 MHz, CDCl3): d = 6.8−7.8 (br, 2H), 0.6−2.0 (br,
Compound 3. In a 100 mL two-neck round-bottom flask,
compound 2 (1.2 g, 5.7 mmol) was dissolved in 30 mL of
dehydrotetrahydrofuran (THF) under argon protection. The flask
was kept at −20 °C; 12.7 mL of 1 M diethyl ether solution of 3,7-
dimethyloctylmagnesium bromide was added slowly. Then, the
temperature was raised to room temperature and kept stirring for 6
h. The reaction was stopped by adding 20 mL of water into the
solution, and the organic part was extracted by ethyl acetate. The ethyl
acetate solution was dehydrated with sodium sulfate. The solution was
then passed through a silica gel column, and the solvent was removed.
1
2.8 g of compound 3 was obtained as light yellow oil (yield 90%). H
NMR (CDCl3, 400 MHz): 8.42 (br, 1H), 7.27 (d, 1H), 7.21 (d, 1H),
6.98 (d, 1H), 6.74 (d, 1H), 2.74 (br, 1H), 1.92 (m, 4H), 1.55−1.00
(br, 20H), 0.92 (s, 6H), 0.89 (s, 12H).
Compound 4. In a 100 mL two-neck round-bottom flask,
compound 3 (1.5 g, 3.0 mmol) was dissolved in toluene (30 mL) in
a flask under argon protection. 100 mg of sodium p-toluenesulfonic
acid monohydrate was added into the solution and stirred for 1.5 h at
110 °C. The solution was cooled down to room temperature, and 50
mL of water and 30 mL of toluene were added to extract the organic
part. The toluene solution was dried with sodium sulfate, and then the
solvent was removed. The compound was purified by silica gel
chromatography using hexane as the eluent to obtain a yellow oil (1.3
42H). Mn = 28.5 kDa (Figure S3); polydispersity = 2.2. PBDT−DFBT
and PCPDT−DFBT were synthesized using the same procedure but
much shorter polymerization time (∼20 min).
Materials Characterization, Device Fabrication, and Meas-
urements. See Supporting Information for the details.
1
g, yield 95%). H NMR (CDCl3, 400 MHz): 6.98 (d, 1H), 6. 93 (d,
1H), 6.68 (d, 1H), 6.60 (d, 1H), 1.90 (m, 4H), 1.54−1.01 (br, 20H),
0.89 (s, 6H), 0.85 (s, 12H) (Figure S1).
Compound M1. In a 100 mL two-neck round-bottom flask,
compound 4 (0.58 g, 1.2 mmol) was dissolved in THF (20 mL) in a
flask under argon protection. Keep the solution at −78 °C. 1.7 mL (2.7
mmol) of n-butyllithium was dropped into the solution slowly. The
solution was stirred at −78 °C for 30 min and room temperature for 2
h. Then 0.92 mL of tributyltin chloride (3.4 mmol) was added at −78
°C in one portion. Stirring was maintained at room temperature for 6
h, and then 30 mL of water was added to quench the reaction. 30 mL
of hexane was added to extract the organic part, and the solvent was
removed under vacuum. The product was purified by silica gel column
with hexane as eluent. (In advance, the silica gel was dipped into
hexane contains 10% triethylamine for 1 h and flushed out with
hexane.) After removing the solvent, M1 was obtained as brownish oil
(1.18 g, yield 92%). 1H NMR (CDCl3, 400 MHz): 6.71 (d, 1H), 6. 68
(d, 1H), 1.96−1.80 (br, 4H), 1.64−1.00 (br, 56H), 0.89−0.82 (m,
36H) (Figure S2).
Compound 6. In a 500 mL two neck round-bottom flask,
compound 5 (6.0 g, 41.7 mmol) was dissolved in 60 mL of pyridine in
a flask under argon protection. 6.2 mL (85.4 mmol) of thionyl chloride
was added in 20 min at 0 °C. The mixture was stirred at room
temperature for 6 h. 200 mL of water and 200 mL of DCM were
added to extract the product. The organic part was washed with water
2−3 times to remove pyridine. The solvent was removed under
vacuum, and the product was purified by silica gel chromatography
using a hexane and ethyl acetate mixture (4:1, v:v) as the eluent to
obtain a white solid (3.3 g, yield 46%). 1H NMR (CDCl3, 400 MHz):
7.75 (t, 2H). 19F NMR (CDCl3, 400 MHz): −128.3 (s, 2F). GC-MS:
172.0 [M+] (purity >98%).
RESULTS AND DISCUSSION
■
Material Design and Synthesis. The synthetic routes of
DTP, DFBT, and related polymers are shown in Scheme 1. The
detailed synthesis procedure is described in the Experimental
Section.9 Monomers M3 and M4 were synthesized using
reported methods.6a,8b First, compound 2 was obtained via
Baeyer−Villiger oxidation by sodium perborate monohydrate
from compound 1 at room temperature with yield ∼30%.10
The low yield of this step is possibly due to the oxidation of
other positions on compound 1. Then, compound 2 was
treated with excess Grignard reagent at room temperature to
yield compound 3 with 90% yield. The solublizing side chain,
3,7-dimethyloctyl (DMO), can be incorporated onto the DTP
unit. Next, the ring-closing reaction was carried out by adding
sodium p-toluenesulfonic acid (p-TSA) into a toluene solution
of compound 3 and refluxing for 1−2 h. The DTP compound
(compound 4) was purified by silica gel chromatography 2−3
times using hexane as the eluent and was obtained as a yellow
oil with high yield. Monomer M1 was made using the
conventional method: (1) Lithiation by n-butyllithium at low
temperature and (2) addition of tin compound (typically
trimethyltin chloride) to the mixture to form the ditin
monomer. However, the tin compounds are usually difficult
to purify by silica gel chromatography due to their poor
stability.3d Here, we chose tributyltin instead of trimethyltin to
increase the stability to the silica gel, and also, we treated the
silica gel with triethylamine before use to passivate the weak
acidity. By doing these, very pure compound M1 can be
obtained by passing through a deactivated silica gel column
Compound M2. In a 100 mL two neck round-bottom flask,
compound 6 (2.5 g, 14.5 mmol) was dissolved in fuming sulfuric acid
(30 mL) in a flask under nitrogen protection. 7 mL of bromine was
added into the flask in one portion. The mixture was stirred at 60 °C
for 24 h. The mixture was cooled down and then poured it into 500
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dx.doi.org/10.1021/ma400452j | Macromolecules 2013, 46, 3384−3390