Shen et al.
FULL PAPER
Aesar Chemical Co. N,N-Dimethylformamide (DMF),
-
1
1278, 1155, 1003, 956, 820, 630, 588, 543, 525 cm .
tetrahydrofuran (THF) and ferric chloride (FeCl
3
) were
Anal. calcd for C12 : C 33.18, H 1.84, N 6.45;
8 2 2
H N I
from Sinopharm Chemical Reagent Co., Ltd. 4-Iodo-
aniline was purchased from Fluka. All materials were of
analyitical grade and used as received unless otherwise
noted. Diisopropylamine was distilled from KOH.
found C 32.86, H 1.99, N 6.17.
Polymer (PPEPAPE)
(0.1000 g, 0.2304 mmol), 1,4-diethynyl-2,5-didodecyl-
oxybenzene (0.1138 g, 0.2304 mmol), Pd(PPh (0.0133
4,4'-Diiodoazobenzene
3 4
)
1
,4-Diethynyl-2,5-didodecyloxybenzene was synthe-
g, 0.0115 mmol) and CuI (0.0022 g, 0.0115 mmol) were
placed into pre-dried 50 mL three-necked round bottom
flask. The system was deoxygenated by three cycles of
vacuum-argon cycling. 10 mL of anhydrous THF and 2
mL of distilled diisopropylamine were added into the
system. The mixture was stirred at 65 ℃ for 20 h under
argon atmosphere. The reaction mixture was added into
large amount of methanol. The crude product was re-
dissoved with THF and precipitated out of methanol for
several times. The resulting polymer was dried in vac-
2
0
sized according to the literature.
General methods
1
H NMR spectra were recorded on an Inova 400
MHz NMR spectrometer. FTIR spectrum of the polymer
was obtained on a Nicolet 6700 FT-IR spectrophotome-
ter (thermo). The samples were prepared by adding
monomers or polymer into KBr, and the mixture was
ground to a fine power and pressed to form disks. The
elemental analysis was carried out on a Carlo-Erba
EA-1110. The molecular weight was determined on a
Waters 1515 gel permeation chromatograph with THF
as the mobile phase and PS as the standard. The UV-Vis
spectra were obtained on a Hitachi U-3900/3900H spec-
trophotometer. The solution UV-Vis and fluorescence
uum to obtain the final product as reddish powders (0.1
1
g, yield 65%). H NMR (CDCl ) δ: 7.85—8.1 (4H), 7.6
3
—7.85 (4H), 6.9—7.2 (2H), 3.4—4.1 (4H), 0.85—1.95
(46H); IR (KBr) ν: 2922, 2850, 2200, 1594, 1504, 1455,
-
1
1412, 1383, 1273, 1215, 1023, 847, 802, 721, 554 cm .
4
4
M : 0.97×10 , M : 2.26×10 , PDI: 2.34.
n
w
measurement were carried out on CHCl
3
solution of
4,4'-diiodoazobenzene or polymer with a concentration
Results and discussion
-
5
of 1×10 mol/L (with respect to the repeating unit for
polymer systems, the same below). The solid UV-Vis
and fluorescence measurement were carried out on the
PPEPAPE film on quartz slide prepared by drop-casting
The polymer PPEPAPE was prepared by a step
growth polymerization employing the palladium-cata-
lyzed Sonogashira coupling of 4,4'-diiodoazobenzene
and 1,4-diethynyl-2,5-didodecyloxybenzene, as shown
-
3
or spin-coating with 1×10 mol/L of PPEPAPE in
2
1
-
3
in Scheme 2. The resulting polymer is of reddish
powder and very soluble (≥10 mg/mL) in common or-
ganic solvents such as THF and chloroform. 1,4-
Diethynyl-2,5-didodecyloxybenzene was synthesized
from 1,4-hydroquinone in four steps as described in the
CHCl
3
, or 1×10 mol/L of PPEPAPE and 10 mg/mL
3
of PMMA codissolved in CHCl . The spin coating was
carried out on a Spin-coater KW-4A from Chemmat
Technology, started with 6 s at the rate of 400 r/min and
followed by 10 s at the rate of 2000 r/min. Morphologi-
cal studies of the films were carried out using a Hitachi
S-4700 scanning electron microscope (SEM). Samples
for SEM were sputter-coated with a thin layer of Au/Pd
prior to the observations to prevent samples-charging
problems. The films for SEM were prepared according
to the same procedure as in the photophysical study ex-
cept using the regular glass slides as the substrate.
2
0
literature. 4,4'-Diiodoazobenzene was quickly pre-
pared with a mild reaction condition through a slight
modification of a previous literature, by stirring the re-
action mixture under room temperature for 1 h (Scheme
2
2
3
).
Scheme 2 Synthetic strategy of PPEPAPE
Synthesis
4
,4'-Diiodoazobenzene
.566 mmol), HgO (1.4863 g, 6.849 mmol) and I
1.7397 g, 6.849 mmol) were placed into a round bottom
with 50 mL CH Cl inside. The mixture was stirred un-
der room temperature for 1 h. The reaction mixture was
filtered and the solid was washed by CH Cl . The com-
bined filtrate was washed by dilute Na and then
water in a separatory funnel. The organic layer was col-
lected and dried over anhydrous Na SO . The solvent
4-Iodoaniline (1.000 g,
4
(
2
2
2
2
2
2 2 3
S O
2
4
was removed by rotary evaporation. The crude product
was purified by running chromatography on silica gel
Scheme 3 Synthetic strategy of 4,4'-diiodoazobenzene
2 2
with eluent composed by petroleum ether and CH Cl
(
V∶V=2∶1). The final product was orange solid (0.3
1
3
g, yield 30%). H NMR (CDCl ) δ: 7.86 (d, 4H, Ar-H),
7
.64 (d, 4H, Ar-H); IR (KBr) ν: 1575, 1470, 1393, 1296,
1
280
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Chin. J. Chem. 2010, 28, 1279— 1283