Photo-crosslinkable polymers as hole-transport materials for organic light-emitting diodes

Article abstract of DOI:10.1039/b110088m

A bis(diarylamino)biphenyl-functionalised methacrylate has been synthesised and polymerised to give a hole-transport polymer; copolymerisation with a chalcone- or cinnamate-functionalised methacrylate affords photocrosslinkable hole-transport polymers that become insoluble upon exposure to ultra-violet irradiation. Organic light-emitting diodes (OLEDs) were fabricated based on both crosslinked and non-crosslinked hole-transport polymers, and the performances of the devices were evaluated.

Full text of DOI:10.1039/b110088m

View Article Online / Journal Homepage / Table of Contents for this issue
Photo-crosslinkable polymers as hole-transport materials for
organic light-emitting diodes
Ya-Dong Zhang,a Richard D. Hreha,a Ghassan E. Jabbour,b Bernard Kippelen,b
N. Peyghambarianb and Seth R. Marder*a,b
aDepartment of Chemistry, The University of Arizona, Tucson, AZ 85721, USA
bOptical Sciences Center, The University of Arizona, Tucson, AZ 85721, USA
Received 5th November 2001, Accepted 11th April 2002
First published as an Advance Article on the web 3rd May 2002
A bis(diarylamino)biphenyl-functionalised methacrylate has been synthesised and polymerised to give a hole-
transport polymer; copolymerisation with a chalcone- or cinnamate-functionalised methacrylate affords photo-
crosslinkable hole-transport polymers that become insoluble upon exposure to ultra-violet irradiation. Organic
light-emitting diodes (OLEDs) were fabricated based on both crosslinked and non-crosslinked hole-transport
polymers, and the performances of the devices were evaluated.
photo-crosslinking or thermal crosslinking reactions.8 The
Introduction
photo-crosslinking technique is widely used in the casting
industry and in photo-resist technology and can allow for
the photo patterning of pixels. Recently, photo-crosslinkable
side-chain polymers9,10 and low molecular weight glass com-
pounds11,12 have been reported for OLEDs. Thermally cross-
linkable oligomers and polymers have also been reported.13
Here we report on the synthesis, characterisation and device
performance in two-layer LEDs of a set of photo-crosslinkable
side-chain acrylate polymers containing a bis(diarylamino)-
biphenyl group as hole-transport agent, and cinnamate14 and
chalcone15 groups as photo-crosslinking groups.
Light-emitting diodes (LEDs) based on organic small mole-
cules1,2 and polymeric materials3,4 have recently attracted
much attention because of their potential for use in flat panel
displays. The most efficient devices to date are multilayer
structures composed of hole-transport, emitting, and electron-
transport layers sandwiched between two electrodes.5,6 OLEDs
based upon small molecules are generally fabricated by vapor
deposition. Polymer-based OLEDs are often fabricated by wet
methods such as spin-coating. A requirement for fabricating
multilayer devices by such techniques is that application of a
subsequent layer does not result in the dissolution of layers
that have been applied in previous steps. One approach to
circumventing this problem is to decrease the solubility of the
layer subsequent to its deposition. The precursor-polymer
route which has been used extensively for fabrication of LEDs
with the poly(p-phenylenevinylene) (PPV) system is an excel-
lent example of such an approach.7 A soluble PPV precursor is
coated onto indium tin oxide (ITO) substrate and thermally
converted into an insoluble PPV film. Alternatively, soluble
polymers can be converted into insoluble polymers by either
Results and discussion
The synthesis and molecular structures of methacrylate mono-
mers with hole-transport moieties and crosslinking moieties are
shown in Schemes 1 and 2. The monomers 5, 8a and 8b were
synthesised from hydroxy-functionalised compounds by reac-
tion with methacrylic acid, using 1,3-dicyclohexylcarbodiimide
(DCC) as a dehydrating agent and 4-dimethylaminopyridine
(DMAP) as a catalyst. Pure monomer 5 was obtained by
Scheme 1 Synthesis of bis(diarylamino)biphenyl-functionalised methacrylate monomer, 5.
DOI: 10.1039/b110088m
J. Mater. Chem., 2002, 12, 1703–1708
This journal is # The Royal Society of Chemistry 2002
1703

View Article Online
Scheme 2 Synthesis of monomers 8a and 8b with crosslinkable units.
recrystallisation of the crude product from a tetrahydrofuran
(THF)–methanol solution (purification on silica gel should be
avoided as the compounds decompose on the silica gel
support). Compound 4 was obtained by reduction of 3 with
sodium borohydride. 4,4’-Bis{N-phenyl-N-(4-methylphenyl)-
amino}biphenyl, 2, was synthesised employing an Ullmann
condensation reaction starting from N,N’-diphenylbenzidine,
1, and 4-iodotoluene. A formyl group was introduced into 2
to yield compound 3 via a Vilsmeier reaction employing
N,N-dimethylformamide (DMF) and phosphorus oxychloride.
Alcohols with crosslinkable units, 7a and 7b, were synthesised
utilising nucleophilic substitution of the corresponding phe-
nols, 6a and 6b, on 3-bromopropanol. The monomer 5 was
homopolymerised or copolymerised with 30% (mole ratio) of
crosslinkable monomers, 8a and 8b, using 2,2’-azobis(isobutyro-
nitrile) (AIBN) as an initiator under nitrogen at 60 uC for 60 h
(as shown in Scheme 3). All of the polymers were purified by
precipitation three times into methanol, once from benzene and
twice from THF. The polymers 9 and 9a were obtained as white
powders, and the polymer 9b was obtained as a pale yellow
powder. The structures of the compounds and polymers were
confirmed by NMR and elemental analysis (as shown in the
Experimental section).
The molecular weights of the polymers were measured by
gel permeation chromatography (GPC) with THF as eluant.
The weight-average molecular weights (Mw) and number-
average molecular weights (Mn) of these polymers versus linear
polystyrene standards are reported in Table 1. All the polymers
with high molecular weights show good solubilities in a variety
of common organic solvents such as benzene, THF, toluene,
chloroform, and dichloromethane. The glass-transition tem-
peratures (Tg) of the polymers were determined by differential
scanning calorimetry (DSC). Of these polymers, homopolymer
9 exhibits the highest Tg. It is evident that the incorporation
of crosslinking moieties serves to reduce the Tg. No evidence
of other thermal processes such as the melting of a side chain
Table 1 The glass transition temperatures (Tg) and molecular weights,
referenced to polystyrene standards, for the polymers 9, 9a and 9b
Polymer
Tg/uC
Mw
Mn
Mw/Mn
9
9a
9b
155
137
133
720 000
810 000
750 000
170 000
180 000
180 000
4.2
4.5
4.2
Scheme 3 Synthesis of the polymers.
1704
J. Mater. Chem., 2002, 12, 1703–1708

View Article Online
crosslinking units, showed almost no absorbance change at the
absorption maxima after UV-irradiation for 25 min (as shown
in Fig. 1a), suggesting that the bis(diarylamino)biphenyl
moiety is relatively photochemically stable under these cross-
linking conditions. Thus, we attributed the decrease of the
absorption of the polymers 9a (as shown in Fig. 1b) and 9b
(as shown Fig. 1c) predominantly to the photo-induced 2 1 2
cycloaddition reaction of the crosslinkable groups.
Irradiated polymer 9a and 9b films on quartz substrates were
used to demonstrate the insolubility of the polymers after UV
irradiation. The UV absorption spectra were acquired after
dipping the films in THF for different times. Even after soak-
ing the irradiated polymer films for 20 minutes, almost no
measurable decrease in absorption (as shown in Fig. 2) was
observed, suggesting that the polymers were crosslinked. In
contrast, for the uncrosslinked films of the polymers 9a and 9b
on quartz, it was found that the absorption intensities were
dramatically decreased to almost zero after dipping films in
THF for 1 minute. These observations demonstrate that the
crosslinked copolymers are insoluble in THF. Similarly,
crosslinked 9a and 9b films on quartz substrates were dipped
into other solvents, such as chloroform and dichloromethane,
for 1 minute to 3 hours, and also showed almost no absorption
changes in UV spectra.
To investigate the EL properties, OLEDs based on uncross-
linked polymers (9, 9a, and 9b) and crosslinked polymers
(derived by irradiation of 9a and 9b) as the hole-transporting
materials and tris(8-hydroxyquinolate)aluminium (Alq3) as the
electron-transporting and emitting material were fabricated.
The films (y50 nm thickness) were prepared from 9, 9a, and 9b
by spin-coating chloroform solutions onto ITO with sheet
resistance of 30 O/% (Donnelly Corporation). The photo-
crosslinked films of 9a and 9b were obtained by 10 minute UV-
irradiation (365 nm, 7 W) followed by rinsing with chloroform.
The Alq3 films (y60 nm thickness) were then deposited on the
top of both the uncrosslinked hole-transporting polymer films
Fig. 1 UV-vis. spectra of thin films of (a) 9, (b) 9a, and (c) 9b after
irradiation with UV light for various time periods.
was observed in the temperature range investigated (from 20 to
260 uC) suggesting that the polymers as prepared are amorphous.
Thin films of polymers 9, 9a and 9b on a quartz substrate
were obtained by spin-coating at 3000 rpm from THF solution
(20.0 mg in 1 cm3 of THF). The polymer films were irradiated
with an unfiltered handle UV source (365 nm, 7 W, UVGL-25)
for visualising thin-layer-chromatography plates. The films
were kept at a distance of 2 cm from the UV lamp. The
crosslinking of the polymers upon UV-irradiation was followed
by UV spectroscopy. The decrease of the absorbances at 310 nm
(9a) and 343 nm (9b), attributed to the UV-induced 2 1 2
cycloaddition reactions of cinnamate and chalcone groups
respectively, was used to monitor the progress of crosslinking.
Because the absorptions of cinnamate and chalcone groups
overlap with the absorption of the substituted-diaminobiphenyl
moieties, the decrease of the absorbance could be attributed
to the contributions of 2 1 2 cycloaddition reactions of
crosslinking units and/or photo-decomposition of bis(diaryl-
amino)biphenyl moieties. In order to identify the extent of
decomposition of bis(diarylamino)biphenyl moieties, homo-
polymer 9, without crosslinkable units, was synthesised for
comparison with 9a and 9b. A film of polymer 9 was subjected
to the conditions described above. Polymer 9, which has no
Fig. 2 UV-vis spectra of irradiated thin films of (a) 9a and (b) 9b before
and after dipping in THF.
J. Mater. Chem., 2002, 12, 1703–1708
1705

View Article Online
and crosslinked hole-transporting polymer films under a high
vacuum (about 1026 Torr). Mg was then deposited as a cathode
on the top of Alq3 films. Six devices with bilayer structures were
constructed according to procedures above with the various
hole transporting polymers as shown in Table 2.
The emission of all the devices corresponded to the typical
Alq3 emission spectrum,1 resulting in green OLEDs. The
current–voltage (I–V), luminescence–voltage (L–V) and the
quantum efficiency–voltage characteristics for the devices C
and D are shown in Fig. 3 (similar results have been obtained
for E and F, but the data are not shown). The operating voltages
for these devices, defined here as the voltage at which the light
is first detected (5 cd m22), are roughly 4 V. The brightness and
current densities of these bilayer devices increases with the
applied voltage. It should be noted that the brightness and the
quantum efficiency of the devices, D and F, fabricated with
crosslinked hole-transport films, were lower than the devices, C
and E, fabricated with uncrosslinked polymer hole-transport
films. Such a decrease of the performance has also been
observed for other crosslinkable polymers.10 It was found that
device B, based on UV-irradiated 9 as the hole-transporting
layer, also shows lower performance than device A based on
non-irradiated 9. However, the degree of the performance
decrease from device A to device B was smaller than the
decreases in going from C to D or from E to F (Table 2).
These results may suggest that the decreases in performance of
devices are due to the slight UV-decomposition of the hole-
transporting moieties and film morphology changes during
photo-crosslinking. It is well known that the performance of
OLEDs is very sensitive to the impurities in the materials used
and layer morphology changes. Compared with other OLEDs
based on photo-crosslinked hole transport films, our devices
exhibit much higher brightness and quantum efficiencies.10,12
Table 2 summarises the device data. Detailed research work on
photo-decomposition and morphology changes is in progress.
Several approaches can be tried to improve the decrease in the
LED performance: using photo-stable hole-transport units,
optimizing the ratio of photo-crosslinkable units, using a sensi-
tizer for photocrosslinking at a long wavelength range and
using a more active crosslinkable unit to reduce the irradiation
time.
Fig. 3 Device characteristics for the devices C and D based on non-
irradiated and UV-irradiated 9a respectively.
In conclusion, hole-transport polymers with cinnamate and
chalcone groups as photo-crosslinking moieties have been
synthesised and characterised. In this type of polymer, the
molar ratio of different crosslinkable moieties can be varied.
Insoluble crosslinked films have been obtained by UV-
irradiation and demonstrated by UV-vis spectroscopy. The
LEDs based on these crosslinked hole-transport layers show
reasonable performance under an applied electric field. We are
currently working on optimizing both the photo-crosslinkable
units and hole-transport units for improving device perfor-
mances for the photo-crosslinked materials. Epoxy and
oxetane groups will be used for minimising the morphology
changes. The crosslinkable materials allow us to fabricate and
study multilayer devices with spin-coating. In future work,
crosslinkable polymers for light emission and electron trans-
port will be synthesised for the fabrication of spin-coated
multilayer devices.
Experimental
Chemicals received from commercial sources were used with-
out further purification. NMR spectra were recorded with a
Varian Unity Plus at 500 MHz (1H) and 126 MHz (13C{1H })
in CDCl3. UV-vis spectra were recorded on thin films on
quartz substrates with a Hewlett Packard 8453 spectrometer.
Glass-transition temperatures were determined by thermal
analysis using a Shimadzu DSC-50 differential scanning calori-
meter at a scan rate of 10u min21. The molecular weights of the
polymers and polydispersities were determined via GPC
analyses using JORDI-Gel DVD 500A gel column, calibrated
with polystyrene standards with molecular weight range of
104–108.
Table 2 Device structures and performance
Hole-transport
polymer
Current density at
9.0 V (mA cm22
Max. ext. quant eff.
(% photons/e)
Light output at
10 V (cd m22
)
Device
)
A
B
C
D
E
F
9
289
219
310
244
231
157
1.0 (at 7.4 V)
0.8 (at 7.6V)
1.0 (at 7.4 V)
0.7 (at 7.6 V)
0.6 (at 7.8 V)
0.4 (at 8.4 V)
12 000
10 000
15 000
8 900
6 500
3 800
UV-irradiated 9
9a
UV-irradiated 9a
9b
UV-irradiated 9b
1706
J. Mater. Chem., 2002, 12, 1703–1708

View Article Online
4,4’-Bis{N-phenyl-N-(4-methylphenyl)amino}biphenyl, 2
was stirred at that temperature for 10 h. The reaction mixture
was added to methanol (250 cm3) and the product was
precipitated. The solid product was collected and recrystallised
from THF–methanol. After collecting and drying under
vacuum, 77.2% (5.2 g) of white product was obtained.
1H NMR d: 7.42 (m, 4 Harom), 7.24 (m, 4 Harom), 7.09 (m, 17
Harom) 6.16 (s, 1 H, -CLC-H), 5.83 (s, 1 H, -CLC-H), 5.12 (s,
2 H, -OCH2), 2.33 (s, 6 H, -CH3), 1.97 (s, 3 H, -CH3) ppm.
13C{1H} NMR d: 167.34, 147.85, 147.82, 146.88, 146.51,
145.06, 144.83, 136.29, 134.75, 134.21, 133.19, 132.87, 130.01,
129.93, 129.40, 129.30, 129.13, 127.21, 127.16, 125.72, 125.22,
125.00, 123.89, 123.72, 123.46, 122.93, 122.35, 66.24, 20.84,
18.39 ppm. Melting point 72–74 uC. Elemental analysis: Calcd.
for C43H38N2O2: C, 84.01; H, 6.23; N, 4.56. Found: C, 84.03;
H, 6.17; N, 4.68%.
To a solution of N,N’-diphenylbenzidine 1 (7.0 g, 20.8 mmol)
and p-iodotoluene (13.0 g, 60.0 mmol) in o-dichlorobenzene
(100 cm3) under nitrogen atmosphere was added copper (14.0 g,
218.8 mmol), K2CO3 (30.0 g, 217.1 mmol) and 18-crown-6
(200 mg) at room temperature, and the resultant mixture was
stirred at 190 uC for 14 h. Then, the inorganic solids were
removed by filtration. These solids were washed with THF four
times. After removal of solvent, the crude product was purified
by column chromatography on silica gel using toluene–hexane
(7 : 3) as solvent. The pure product was obtained in 86% (9.2 g)
yield.
1H-NMR d 7.41 (d, 4 Harom, J ~ 8.0 Hz), 7.23 (d, 4 Harom
J ~ 8.0 Hz), 7.08 (m, 18 Harom), 2.32 (s, 6 H, CH3) ppm.
13C{1H} NMR d: 147.84, 146.79, 145.07, 134.34, 132.82,
129.94, 129.12, 127.15, 124.98, 123.70, 123.51, 122.31, 20.84 ppm.
,
Methyl 4-(3-hydroxypropoxy)cinnamate, 7a
4-[N-(4-Formylphenyl)-N-(4-methylphenyl)amino]-4’-[N-phenyl-
N-(4-methylphenyl)amino]biphenyl, 3
To a solution of 4-hydroxycinnamate 6a (6.0 g, 33.7 mmol) and
3-bromopropanol (5.0 g , 40.7 mmol) in DMF (30 cm3) was
added K2CO3 (10.0 g, 72.5 mmol). The reaction was stirred at
room temperature for 12 h. Water (200 cm3) was added to the
reaction mixture. The precipitate was collected by filtration.
After recrystallisation from an acetone–water mixture, 90.0%
(7.2 g) of 7a was obtained as white crystals.
1H NMR d: 7.64 (d, 1 H, H-CLC, J ~ 16.0 Hz), 7.48 (d, 2
Harom, J ~ 9.0 Hz), 6.91 (d, 2 Harom, J ~ 9.0 Hz), 6.32 (d, 1 H,
H-CLC, J ~ 16.0 Hz), 4.16 (t, 2 H, OCH2, J ~ 7.0 Hz), 3.88
(m, 2 H, OCH2), 3.79 (s, 3 H, OCH3), 2.06 (m, 2 H, CH2), 1.71
(t, 1 H, OH) ppm. 13C{1H} NMR d: 167.78, 160.55, 144.47,
129.65, 126.99, 115.07, 114.68, 65.32, 59.73, 51.53, 31.81 ppm.
Elemental analysis: Calcd. for C12H16O4 (224.25): C, 64.27; H,
7.19. Found: C, 64.43; H, 7.09%.
To DMF (1.4 g, 19.4 mmol) was added POCl3 (3.0 g, 19.6 mmol)
at 0 uC under nitrogen. After addition of POCl3, 4,4’-bis{N-
phenyl-N-(4-methylphenyl)amino}biphenyl, 2 (10.0 g, 19.4 mmol)
in 1,2-dichloroethane (60 cm3) was added and the reaction
mixture was heated at 60 uC for 5 h. After cooling, the reac-
tion mixture was added to water (180 cm3). The product was
extracted with ethyl acetate (100 cm3), and the organic layer
was washed with Na2CO3 solution. After removal of ethyl
acetate, the crude product was purified on a silica gel column
using toluene–ethyl acetate (9 : 1) as the eluant. 57.8% (6.1 g) of
product was obtained.
1H NMR d: 9.80 (s, 1 H, -CHO), 7.66 (d, 2 Harom, J ~ 8.5 Hz),
7.49 (d, 2 Harom, J ~ 8.5 Hz), 7.42 (d, 2 Harom, J ~ 8.5 Hz),
7.11 (m, 19 Harom) 2.36 (s, 3 H, -CH3), 2.35 (s, 3 H, -CH3) ppm.
13C{1H} NMR d: 190.35, 153.31, 147.68, 147.29, 144.93,
144.76, 143.35, 137.10, 135.21, 133.55, 133.02, 131.28, 130.41,
129.96, 129.16, 128.74, 127.60, 127.33, 126.54, 126.05, 125.10,
123.89, 123.17, 122.54, 118.93, 20.97, 20.83 ppm. Elemental
analysis: Calcd. for C39H32N2O: C, 86.00; H, 5.92; N, 5.14.
Found: C, 85.85; H, 5.92; N, 5.25%.
4-(3-hydroxypropoxy)chalcone, 7b
7b was synthesised by the same method as described for 7a
starting from 6b (5.0 g, 22.3 mmol) and 3-bromopropanol
(3.1 g, 22.3 mmol). The crude product was purified by recry-
stallisation from acetone/water. The pure product was obtained
as a pale yellow solid in 91.9% (5.7 g) yield.
1H NMR d: 8.01 (d, 2 Harom, J ~ 8.0 Hz), 7.76 (d, 1 H,
CLC-H, J ~ 16.0 Hz), 7.56 (m, 5 Harom), 7.42 (d, 1 H, CLC-H,
J ~ 16.0 Hz), 6.94 (d, 2 Harom, J ~ 8.0 Hz), 4.15 (t, 2 H,
OCH2, J ~ 6.0 Hz), 3.87 (m, 2 H, OCH2), 2.06 (m, 3 H, OH
and CH2) ppm. 13C{1H} NMR d: 190.61, 160.90, 144.70,
138.35, 132.56, 130.21, 128.52, 128.34, 127.54, 119.63, 114.81,
65.46, 59.86, 31.83 ppm. Elemental analysis: Calcd. for
C18H18O3 (282.33): C, 76.57; H, 6.43. Found: C, 76.48; H, 6.57%.
4-[N-(4-Hydroxymethylphenyl)-N-(4-methylphenyl)amino]-4’-[N-
phenyl-N-(4-methylphenyl)amino]biphenyl, 4
To a solution of 4-[N-(4-formylphenyl)-N-(4-methylphenyl)-
amino]-4’-[N-phenyl-N-(4-methylphenyl)amino]biphenyl, 3 (6.0 g,
11.0 mmol) in THF (40 cm3) was added NaBH4 (2.0 g,
52.9 mmol) in water (5 cm3) at room temperature. The reaction
was stirred at room temperature for 30 min. Water (250 cm3)
was added. The product was extracted with ethyl acetate
(100 cm3), and, after removal of ethyl acetate, the crude product
was purified on a silica gel column using toluene–ethyl acetate
(7 : 3) as the eluant, and 99.7% (6.0 g) of product was obtained.
Methyl 4-(3-methacryloyloxypropoxy)cinnamate, 8a
1H NMR d: 7.42 (d, 4 Harom, J ~ 8.5 Hz), 7.25 (d, 4 Harom
,
Monomer 8a was prepared by the same method as described
for monomer 5 starting from 7a (5.0 g, 21.0 mmol). The crude
product was purified on a silica gel column using hexane/ethyl
acetate (8 : 2) as eluant. After removal of solvents, pure white
product was obtained in 86.7% (5.2 g) yield by recrystallisation
from acetone/water.
1H NMR d: 7.63 (d, 1 H, H-CLC, J ~ 16 Hz), 7.46 (d, 2
Harom, J ~ 9 Hz), 6.90 (d, 2 Harom, J ~ 9 Hz), 6.33 (d, 1 H,
H-CLC, J ~ 16 Hz), 6.11 (s, 1 H, H-CLC), 5.57 (s, 1 H,
H-CLC), 4.35 (t, 2 H, OCH2, J ~ 6.0 Hz), 4.10 (t, 2 H, OCH2,
J ~ 6.0 Hz), 3.79 (s, 3 H, OCH3), 2.19 (m, 2 H, CH2), 1.94 (s,
3 H, CH3) ppm. 13C{1H} d: 167.65, 167.22, 169.47, 144.38,
136.13, 129.65, 127.10, 125.53, 115.20, 114.68, 64.42, 61.27,
51.50, 28.47, 18.25 ppm. Elemental analysis: Calcd. for
C17H20O5 (304.34): C, 67.09; H, 6.62. Found: C, 67.00; H,
6.50%.
J ~ 8.5 Hz), 7.08 (m, 17 Harom), 4.63 (s, 2 H, -OCH2), 2.36 (s,
1 H, -OH), 2.32 (s, 6 H, -CH3) ppm. 13C{1H} NMR d: 147.82,
147.48, 146.83, 146.64, 145.06, 144.95, 134.58, 134.52, 134.25,
132.97, 132.85, 129.96, 129.94, 129.12, 128.24, 127.18, 127.15,
124.99, 123.71, 123.61, 123.56, 123.59, 122.34, 66.90, 21.10 ppm.
Elemental analysis: Calcd. for C39H34N2O: C, 85.68; H, 6.27;
N, 5.12. Found: C, 85.42; H, 6.55; N, 5.03%.
4-[N-(4-Methacryloyloxymethylphenyl)-N-(4-methylphenyl)amino]-
4’-[N-phenyl-N-(4-methylphenyl)amino]biphenyl, 5
To a solution of 4-[N-(4-hydroxymethylphenyl)-N-(4-methyl-
phenyl)amino]-4’-[N-phenyl-N-(4-methylphenyl)amino]biphenyl,
4 (6.0 g, 11.0 mmol), methacrylic acid (1.0 g, 11.6 mmol) in
THF (30 cm3) and DMAP (0.1 g, 0.8 mmol) was added DCC
(2.4 g, 11.7 mmol) at room temperature. The reaction mixture
J. Mater. Chem., 2002, 12, 1703–1708
1707

View Article Online
4-(3-Methacryloyloxypropoxy)chalcone, 8b
Polymer 9b
Monomer 8b was prepared by the same method as described
for monomer 5 starting from 7b (5.0 g, 18.7 mmol). The crude
product was purified on a silica gel column using toluene–ethyl
acetate (9.5 : 0.5) as eluant. After removal of solvents, pure pale
yellow product in 95.4% (6.2 g) was obtained by recrystallisa-
tion from acetone–water.
1H NMR d: 8.00 (d, 2 Harom, J ~ 8.5 Hz), 7.77 (d, 1 H,
CLC-H, J ~ 15.5 Hz), 6.90–7.54 (m, 5 Harom), 7.41 (d, 1 H,
H-CLC, J ~ 15.5 Hz), 6.94 (d, 1 Harom, J ~ 8.5 Hz), 6.11 (s,
1 H, H-CLC), 5.58 (s, 1 H, H-CLC), 4.36 (t, 2 H, OCH2, J ~
6.0 Hz), 4.11 (t, 2 H, OCH2, J ~ 6.5 Hz), 2.19 (m, 2 H, CH2),
1.94 (s, 3 H, CH3) ppm. 13C{1H} NMR d: 190.48, 167.27,
160.80, 144.58, 138.39, 136.16, 132.53, 130.19, 128.52, 128.36,
127.63, 125.59, 119.71, 114.81, 112.69, 64.50, 61.30, 28.49,
18.29 ppm. Melting point 69– 70 uC Elemental analysis: Calcd.
for C22H22O4 (350.41): C, 75.41; H, 6.33. Found: C, 75.23; H,
6.27%.
9b was prepared in analogy to 9 in 91.2% yield starting from
monomer 5 (0.90 g, 1.47 mmol), chalcone monomer (0.22 g,
0.63 mmol) and AIBN (2.70 mg, 0.016 mmol). 1H NMR d: 7.82
(s, br, Harom), 7.63 (d, br, H-CLC), 7.15 (m, br, Harom, H-CLC),
4.79 (s, br, -OCH2), 4.05 (s, br, -OCH2), 3.87 (s, br, -OCH2),
2.25 (s, br, -CH3), 2.12 (s, br, -CH3), 1.93 (m, br, -CH2), 0.80
(m, br, -CH2) ppm. Elemental analysis: Calcd. for
(C43H38N2O2)0.7(C22H22O4)0.3 (535.46): C, 82.32; H, 6.25; N,
3.66. Found: C, 81.57; H, 6.41; N, 3.81%.
This work was supported by the US Office of Naval
Research through the MURI Center for Advanced Multi-
functional Nonlinear Optical Polymers and Molecular Assem-
blies (CAMP), by the Ballistic Missiles Defense Organisation
through AASERT grant # F49620-96-1-0295, and by the NSF
through a CAREER grant (B.K.).
References
1
2
C. W. Tang and S. A. VanSlyke, Appl. Phys. Lett., 1987, 51, 913.
C. Adachi, K. Nagai and N. Tamoto, Appl. Phys. Lett., 1995, 66,
2679.
J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks,
K. Mackay, R. H. Friend, P. L. Burna and A. B. Holmes, Nature,
1990, 347, 539.
D. Braun and A. J. Heeger, Appl. Phys. Lett., 1991, 58, 1982.
V. Bulovic, G. Gu, P. E. Burrows, S. R. Forrest and
M. E. Thompson, Nature, 1996, 318, 29.
Polymer 9
Monomer5(1.00g, 1.63mmol)andAIBN(2.70mg, 0.016mmol)
were dissolved in dry benzene (4 cm3) under nitrogen. The
polymerisation mixture was deoxygenated and was then placed
in an oil bath at 60 uC for 60 h. The polymer 9 was precipitated
into methanol three times. After drying under vacuum, white 9
was obtained in 96.0% (0.96 g) yield.
3
4
5
1H NMR d: 7.17 (s, br, 4 Harom), 7.08 (s, br, 4 Harom), 6.90
(m, br, 17 Harom), 4.77 (s, br, 2 H, -OCH2), 2.20 (s, br, 6 H, 2 6
CH3), 2.11 (s, br, 3 H, -CH3), 0.77 (m, br, 2 H, -CH2) ppm.
Elemental analysis: Calcd. for C43H38N2O2: C, 84.01; H, 6.23;
N, 4.56. Found: C, 84.09; H, 6.53; N, 4.70%.
6
7
R. C. Kwong, S. Sibley, T. Dubovoy, M. Baldo, S. R. Forrest and
M. E. Thompson, Chem. Mater., 1999, 11, 3709.
E. Buchwald, M. Meier, S. Karg, P. Posch, H. W. Schmidt,
P. Strohriegl, W. Riess and M. Schwoerer, Adv. Mater., 1995, 7,
839.
H. R. Allcock, Chem. Mater., 1994, 6, 1476.
X. C. Li, T. M. Yong, J. Gruner, A. B. Holmes, S. C. Moratti,
F. Cacialli and R. H. Friend, Synth. Met., 1997, 84, 437.
8
9
Polymer 9a
10 E. Bellmann, S. E. Shaheen, S. Thayumanavan, S. Barlow,
R. H. Grubbs, S. R. Marder, B. Kippelen and N. Peyghambarian,
Chem. Mater., 1998, 10, 1668.
11 M. S. Bayerl, T. Braig, O. Nuyken, D. C. Muller, M. Grob and
K. Meerholz, Macromol. Rapid Commun., 1999, 20, 224.
12 A. Bacher, C. H. Erdelen, W. Paulus, H. Ringsdorf, H. W. Schmidt
and P. Schuhmacher, Macromolecules, 1999, 32, 4551.
13 G. Klarner, J.-I. Lee, V. Y. Lee, E. Chan, J.-P. Chen, A. Nelson,
D. Markiewic, R. Siemens, J. C. Scott and R. D. Miller, Chem.
Mater., 1999, 11, 1800.
9a was prepared in analogy to 9 in 91.7% yield starting from
monomer 5 (0.90 g, 1.47 mmol), cinnamate monomer (0.19 g,
0.63 mmol) and AIBN (2.70 mg, 0.016 mmol).
1H NMR d: 7.50 (d, br, H-CLC), 7.25 (s, br, Harom), 7.12
(s, br, Harom), 6.90 (m, br, Harom), 6.18 (d, br, H-CLC), 4.79
(s, br, -OCH2), 4.01 (s, br, -OCH2), 3.86 (s, br, -OCH2), 3.64
(s, br, -OCH3), 2.24 (s, br, -CH3), 2.16 (s, br, -CH3), 1.97 (s, br,
-CH2), 0.81 (m, br, -CH2) ppm. Elemental analysis: Calcd. for
(C43H38N2O2)0.7(C17H20O5)0.3 (521.64): C, 81.05; H, 6.30; N,
3.76. Found: C, 80.72; H, 5.83; N, 3.99%.
14 L. M. Minsk, J. G. Smith, W. P. Van Deusen and J. F. Wright,
J. Appl. Polym. Sci., 1959, 11, 302.
15 C. C. Unruh, J. Appl. Polym. Sci., 1959, 6, 358.
1708
J. Mater. Chem., 2002, 12, 1703–1708