Macromolecules
Article
molecular sieves prior to use. All other chemicals were acquired from
Aldrich and used without further purification. All reactions were
carried out under argon.
C16H12O2, 236.0837; found, 236.0834. IR: 739, 831, 858, 963, 1041,
1174, 1203, 1229, 1332, 1376, 1449, 1484, 1590, 3284 cm−1.
9,10-Diethynylanthracene (10). Monomer 10 was synthesized in
the same manner as that given for 4, but with 9 as starting material
with some modification explained below. Column 1: 100% Hex
(further purified by recrystallization from ethanol to afford
disubstituted material); purified product was stored as the silyl-
protected intermediate. Because of the instability of 10, this material was
deprotected and immediately stannylated and polymerized. The material
was protected from light during deprotection, and after a reaction
period of 1 h, the reaction mixture was quickly passed through a silica
plug. The solvent was removed by rotary evaporation, and 10 was
collected as a yellow solid (0.1571 g, 0.69 mmol, 61% yield) and
immediately used in the next step. 13C NMR (400 MHz, CDCl3) δ:
132.90, 127.49, 127.46, 118.23, 90.34, 80.64 ppm. 1H NMR (400
MHz, CDCl3) δ: 8.61 (m, 4H), 7.62 (m, 4H), 4.07 (s, 2H) ppm. IR:
663, 776, 859, 980, 1029, 1170, 1167, 1222, 1370, 1435, 1623, 3280
cm−1.
Polymer P2. A solution of 1 (0.0216 g, 0.17 mmol) and n-BuLi
(0.43 mL of 1.6 M in Hex, 0.69 mmol) was allowed to stir in 2 mL of
dry THF at −78 °C for 0.5 h. To this solution was added tributyltin
iodide (0.19 mL, 0.66 mmol), and the mixture temperature was
allowed to reach room temperature while stirring for 2 h. The solution
was poured over water and extracted with DCM. The DCM extracts
were combined, dried over NaSO4, and the solvent was removed by
rotary evaporation. Proton NMR showed satisfactory conversion to 2,
and this material was dissolved with 12 (0.1675 g, 0.17 mmol) in 2 mL
of dry toluene. The mixture was subjected to three freeze, pump, and
thaw cycles. Pd(PPh3)4 (0.0100 g, 5 mol %) was added, and the
solution was heated at 90 °C. The polymerization progress was
monitored by UV−vis spectroscopy. Once the solution absorbance
bathochromically shifted to its absorbance maximum, iodobenzene
(0.19 mL, 1.7 mmol) was added to the solution, and the reaction
proceeded for an additional 2 h. The toluene was concentrated to a
minimal volume by rotary evaporation, and the crude material was
precipitated with MeOH/2N aqueous HCl (10/1 (v/v)). The solid
was purified with a Soxhlet extraction apparatus using methanol,
acetone, and DCM in succession. The polymers were collected from
the DCM fraction and concentrated to a minimum volume by rotary
evaporation. The polymers were precipitated two more times in
MeOH/2N aqueous HCl (10/1 (v/v)) to yield a bright red solid
(0.1037 g, 0.11 mmol, 64% yield). IR: 724, 767, 793, 839, 930, 1020,
1199, 1226, 1316, 1393, 1395, 1447, 1513, 1578, 1666, 1708, 2206,
2856, 2927, 2960 cm−1. GPC: Mn 18.7, Mw 60.9, PDI 3.3.
Instrumentation. NMR spectra were taken on a Varian Unity 400
spectrometer. Melting points were detected using a MEL-TEMP
apparatus. GPC analyses were performed on polymer solutions in
THF using a Waters Model 510 HPLC pump, two fluorinated
polystyrene columns (IMBHW-3078 and I-MBLMW-03078) arranged
in series, and a Waters 486 tunable absorbance detector (λ = 450 nm).
Calibration was based on polystyrene standards in THF. Absorption
spectra were obtained on an Agilent 8453 UV−vis spectrometer.
Fluorescence measurements were made on a PTI fluorimeter (4 nm
slits) with an 814 photomultiplier detection system using a 75 W
xenon short arc lamp. IR spectra were obtained using polymer solids
on a PerkinElmer Spectrum 100 FT-IR equipped with a universal ATR
(UATR) accessory. Electrochemical cyclic voltammetry was performed
under a nitrogen atmosphere. The cell was equipped with platinum
working, tungsten counter, and silver electrodes. Thin films were
measured in a 0.1 M tetrabutylammonium hexafluorophosphate
(TBAP) MeCN solution at a scan rate of 50 mV s−1 and referenced
to Fc/Fc+ by shifting (Fc*)0/+ to 0.0 V.20 X-ray powder diffraction
(XRD) patterns were obtained with a Scintag X1 theta−theta
diffractometer equipped with a Cu X-ray tube and a solid-state X-ray
detector set to count Cu Kα radiation. Samples were prepared by
smearing a small amount of polymer onto a zero background quartz
plate sample holder. Suitable samples were obtained by methanol
precipitation or slow evaporation from CH2Cl2 to yield a powder and
film, respectively. Both methods gave the same XRD pattern.
2,6-Dibromo-1,5-bis(methoxy)naphthalene (6).21 To a sol-
ution of 2,6-dibromonaphthalene-1,5-diol22 (5.90 g, 19.0 mmol) in
dry, degassed NMP (85 mL) at 0 °C was added NaH (60% mineral oil
dispersion, 1.70 g, 42.0 mmol). After allowing the solution to stir at 0
°C for 5 min, MeI (6.20 g, 44.0 mmol) was added and the solution
warmed to room temperature while stirring overnight. The solution
was poured onto ice (400 g), extracted with diethyl ether, and the
organic fractions were poured through a short neutral alumina plug.
The solvent was removed by rotary evaporation and the crude material
was purified by recrystallization from acetone to yield a light brown
solid (5.24 g, 15.0 mmol, 79% yield); mp 149−156 °C. 13C NMR (400
MHz, CDCl3) δ: 153.68, 131.32, 129.87, 119.68, 113.83, 61.76 ppm.
1H NMR (400 MHz, CDCl3) δ: 7.78 (d, J = 8.0 Hz, 2H), 7.63 (d, J =
8.0 Hz, 2H), 3.99 (s, 6H) ppm. CI-HRMS (positive ion) calculated for
C12H10Br2O2, 343.9048; found, 343.9048.
2,6-Diethynylnaphthalene (4). 3 (0.3258 g, 1.14 mmol) was
dissolved in 11 mL of a 50/50 toluene/TEA solution. The solution
was degassed with argon. Pd(PPh3)2Cl2 (0.1145 g, 15 mol %), CuI
(0.0105 g, 5 mol %), and (tert-butyldimethylsilyl)acetylene (0.3229 g,
2.30 mmol) were subsequently added, and the solution was heated at
reflux for 24 h. The solvent was removed by rotary evaporation, and
the material was passed through a short silica column (column 1: Hex)
to yield a mixture of the disubstituted and monosubstituted protected
alkyne intermediates. This mixture was taken up in 11 mL of THF
with TBAF (2.3 mL of 1.0 M in THF, 2.3 mmol) and stirred at room
temperature for 1 h. The solvent was removed by rotary evaporation,
and the crude material was purified by column chromatography
(column 2: Hex) to afford the desired product as a white solid (0.1508
g, 0.86 mmol, 75% yield); mp 144−148 °C. 13C NMR (400 MHz,
CDCl3) δ: 132.37, 132.03, 129.33, 127.86, 120.45, 83.67, 78.23 ppm.
1H NMR (400 MHz, CDCl3) δ: 7.99 (s, 2H), 7.74 (d, J = 12.0 Hz,
2H), 7.54 (dd, J = 1.3 Hz, J = 8.0 Hz, 2H), 3.18 (s, 2H) ppm. CI-
HRMS (positive ion) calculated for C14H8, 176.0626; found, 176.0626.
IR: 678, 706, 819, 884, 1255, 1364, 1494, 1597, 3268 cm−1.
2,6-Diethynyl-1,5-bis(methoxy)naphthalene (7). Monomer 7
was synthesized in the same manner as that given for 4, but with 6 as
starting material. Column 1: 5% DCM/Hex; column 2: 30% DCM/
Hex; collected as an off-white solid (0.1936 g, 0.82 mmol, 72% yield);
mp 142−147 °C. 13C NMR (400 MHz, CDCl3) δ: 159.04, 130.27,
129.14, 117.85, 111.77, 83.18, 80.31, 61.94 ppm. 1H NMR (400 MHz,
CDCl3) δ: 7.86 (d, J = 8.0 Hz, 2H), 7.49 (d, J = 8.0 Hz, 2H), 4.13 (s,
6H), 3.45 (s, 2H) ppm. CI-HRMS (positive ion) calculated for
Polymer P5. P5 was synthesized using the same procedure and
scale as that given for P2, but with 4 and 12 as starting materials. P5
was collected as a red solid (0.1376 g, 0.14 mmol, 82% yield). IR: 693,
725, 776, 836, 931, 1201, 1222, 1316, 1382, 1447, 1514, 1577, 1666,
1709, 2207, 2855, 2925, 2963 cm−1. GPC: Mn 8.2, Mw 23.0, PDI 2.8.
Polymer P8. P8 was synthesized using the same procedure and
scale as that given for P2, but with 7 and 12 as starting materials. P8
was collected as a purple solid (0.1619 g, 0.15 mmol, 88% yield). IR:
693, 725, 775, 822, 926, 1062, 1200, 1222, 1314, 1352, 1381, 1451,
1573, 1666, 1709, 2191, 2856, 2926, 2960 cm−1. GPC: Mn 14.9, Mw
58.4, PDI 3.9.
Polymer P11. P11 was synthesized using the same procedure and
scale as that given for P2, but with 10 and 12 as starting materials. P11
was collected as a purple solid (0.0698 g, 0.07 mmol, 41% yield). IR:
694, 725, 775, 923, 1212, 1221, 1252, 1312, 1380, 1451, 1575, 1661,
1709, 2179, 2856, 2926, 2961 cm−1. GPC: Mn 3.3, Mw 10.0, PDI 3.0.
RESULTS
■
Design. DAN, benzene, naphthalene, and anthracene were
selected to explore how the physical size and donating
properties influence the properties of conjugated NDI−donor
polymers. DAN and NDI are known to stack in an alternating
fashion14a,16a due to electrostatic complementarity that drives
desolvation effects in polar media.23 Similar self-assembly has
also been observed in a 1:1 complex of an anthracene-based
719
dx.doi.org/10.1021/ma302340u | Macromolecules 2013, 46, 718−726