Synthesis and characterization of photo-cross-linkable hole-conducting polymers

Article abstract of DOI:10.1021/ma048365h

The synthesis and characterization of side-chain polymers functionalized with hole-transporting units and photo-cross-linkable groups, which can be used for solution-based preparation of multilayer organic light-emitting devices (OLEDs), are discussed. The concept deals with triarylamine and oxetane-functionalized styrenes, which are copolymerized by radical polymerization. Four different types of hole-transporting monomers were combined with one cross-linkable monomer in two different ratios, yielding two groups of each four polymers (P1A...P4A and P1B...P4B). The polymers were investigated by NMR spectroscopy, molecular weights were determined by GPC with light scattering, and the thermal properties were measured with differential scanning calorimetry (DSC). Optical characterization by UV-vis and fluorescence spectroscopy was performed. Electrochemical and cross-linking characteristics of the copolymers were investigated to proove this strategy's potential in application for modern multilayer polymer OLEDs. Finally, hole-only devices were prepared for evaluation of the semiconductive performance of the materials.

Full text of DOI:10.1021/ma048365h

1640
Macromolecules 2005, 38, 1640-1647
Synthesis and Characterization of Photo-Cross-Linkable
Hole-Conducting Polymers
Erwin Bacher,† Michael Bayerl,† Paula Rudati,‡ Nina Reckefuss,‡ C. David Mu1 ller,‡
Klaus Meerholz,‡ and Oskar Nuyken*,†
Lehrstuhl fu¨r Makromolekulare Stoffe, Technische Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
D-85747 Garching, Germany, and Institut fu¨r Physikalische Chemie, Universita¨t Ko¨ln,
Luxemburgerstrasse 116, D-50939 Cologne, Germany
Received August 9, 2004; Revised Manuscript Received November 29, 2004
ABSTRACT: The synthesis and characterization of side-chain polymers functionalized with hole-
transporting units and photo-cross-linkable groups, which can be used for solution-based preparation of
multilayer organic light-emitting devices (OLEDs), are discussed. The concept deals with triarylamine
and oxetane-functionalized styrenes, which are copolymerized by radical polymerization. Four different
types of hole-transporting monomers were combined with one cross-linkable monomer in two different
ratios, yielding two groups of each four polymers (P1A...P4A and P1B...P4B). The polymers were
investigated by NMR spectroscopy, molecular weights were determined by GPC with light scattering,
and the thermal properties were measured with differential scanning calorimetry (DSC). Optical
characterization by UV-vis and fluorescence spectroscopy was performed. Electrochemical and cross-
linking characteristics of the copolymers were investigated to proove this strategy’s potential in application
for modern multilayer polymer OLEDs. Finally, hole-only devices were prepared for evaluation of the
semiconductive performance of the materials.
Introduction
caused by polycondensation reactions, which were also
used for generating stable films.24
Modern organic light-emitting diodes (OLEDs) consist
of two or more different layers1 to enhance electro-
optical properties and stability. During processing of the
devices via layer-by-layer coating, the subsequent layer
has to be coated onto the previous layer without altering
it. A useful method to avoid redissolution is to cross-
link the coated layer before applying the next one.2
Cross-linked polymers are used in manifold ways for
OLEDs.3-6 Photo-cross-linking became an especially
common strategy of protecting polymer films against
solvents.7-9 Generally, for the preparation of OLEDs, a
precursor consisting of charge-transporting or emitting
groups and pendant photo-cross-linkable function is
dissolved in a suitable solvent. A certain amount of
photoinitiator is added before this solution is spin-coated
onto a substrate. Then, the layer is dried and finally
cross-linked by irradiation with UV light. After this step,
the next layer can be produced the same way on top of
the first one without altering the original layer and so
on.
For achieving homogeneous and crack-free layers, the
polymerizable group used for this cross-linking should
show only little volume shrinkage, short conversion
time, and nearly quantitative yield. The oxetane unit,
which fulfills the requirements almost ideally, is used
in our work as a pendant cross-linkable group.10 It
shows an ideal combination of cross-linkability on one
hand and processability on the other hand. Further-
more, it is inert to coupling conditions so that conver-
gent synthesis can be carried out. A significant advan-
tage of this photopolymerization-based process is the
absence of any small molecules after cross-linking,
Several strategies are applied in our workgroup to
combine emitting or charge-transporting properties with
cross-linkability: first, cross-linker functionalized low-
molecular-weight charge-transport molecules,11 second,
polymers with emitter or charge transporter as a part
of the backbone are used.12 In this paper, we propose
side-chain-functionalized inert polymer backbones, e.g.,
poly(styrene)s with pendant emitter or charge trans-
porter. In all cases, the cross-linkable groups are placed
in the side chain. The synthesis and characterization
of such copolymers, made from cross-linker- and charge-
transporter-functionalized monomers, are described in
some detail.
Results and Discussion
Monomer Synthesis. Copolymerization of both hole-
conductor- and oxetane-functionalized styrene yields
polymers with pendant charge-transporting and cross-
linkable oxetane units. Advantages of this strategy are
the freedom to choose the polymer, no residues of a
polymerization catalyst, and due to the broad variety
of functionalized monomers, the synthesis of tailor-made
hole-conducting polymers. The different monomer struc-
tures, which have their own individual oxidation po-
tentials, form a “construction kit” which allows for the
synthesis of an optimized polymer for the corresponding
application. However, the dilution of the active functions
by the inert polymer backbone, spacer, and cross-linking
groups should be considered as a possible disadvantage
leading to reduced conductivity.
The electrochemical potential of charge transporters
has to be adapted to the electrode work function and to
the HOMO of the adjacent emitting layer. Variations
of the triarylamine unit allow for fine-tuning of the
redox properties of the hole-transporting layer. The
same cross-linking monomer was applied in each case.
* Author to whom correspondence should be addressed. Phone:
+498928913571. Fax: +498928913562. E-mail: oskar.nuyken@
ch.tum.de.
† Technische Universita¨t Mu¨nchen.
‡ Universita¨t Ko¨ln.
10.1021/ma048365h CCC: $30.25 © 2005 American Chemical Society
Published on Web 02/08/2005

Macromolecules, Vol. 38, No. 5, 2005
Photo-Cross-Linkable Hole-Conducting Polymers 1641
Scheme 1. Synthesis of Oxetane-Functionalized Monomer C1
Scheme 2. Synthetic Pathways to Hole-Conducting Monomers H1-H4
Earlier work showed that the cross-linking is improved
with 4-vinyl benzyl chloride, yielding the desired prod-
uct C1 (Scheme 1). A common C-N coupling route, the
Hartwig-Buchwald amination, is used for the synthesis
of hole-conducting monomers (Scheme 2).16-18 Synthesis
of H1 starts with the bromination of triphenylamine by
N-bromosuccinimide (NBS), which is highly regioselec-
tive, yielding 2b. After two C-N coupling steps, first
with aniline (2b f 2c) and second with protected
4-bromobenzyl alcohol, a hydroxymethyl-substituted
tetraphenyl phenylenediamine was obtained after depro-
by using a relatively long alkyl spacer between the
functional unit and the oxetane unit, ultimately
giving sufficient diffusional mobility to the oxetanes to
react.13 We found that hexyl spacers gave excellent
results.
The oxetane-functionalized monomer C1 was synthe-
sized by a two-step etherification. First, 3-chloromethyl-
3-ethyl oxetane 1a14,15 was reacted with 1,6-hexanediol
yielding 1b, and then the resulting product was coupled

1642 Bacher et al.
Macromolecules, Vol. 38, No. 5, 2005
Scheme 3. Copolymerization of Styrene-Functionalized Hole Conductor H1-H4 and Cross-Linker C1, Leading to
Polymers P1A/B-P4A/B
Table 1. Data for P1A/B-P4A/B
P1A
P1B
P2A
P2B
P3A
P3B
P4A
P4B
Mn (104 g/mole)
Mw/Mn
λmax (nm) absorption
λmax (nm) fluorescence
yield (%)
11.1
1.92
320
406
85
10.7
2.30
11.3
2.26
360
422
92
7.6
9.5
8.8
14.6
2.18
350
444
85
12.2
1.82
2.39
2.31
345
457
90
2.08
88
95
95
87
N content (%) calcd
found
3.1
4.2
2.9
3.8
2.6
3.3
2.8
3.5
3.1
54
0.98/1
4.1
2.9
67
1.08/1
3.8
2.6
3.1
2.7
70
1.05/1
3.5
Tg (°C)
74
83
72
86
84
molar ratio H/Ca
2.89/1
3.05/1
1.08/1
3.11/1
3.10/1
a Calculated from the ratio between 1H NMR Integrals of the oxymethylene groups of cross-linker (δ ) 3.4) and all oxymethylene
groups (δ ) 3.4 and 4.4)
tection of the OH group (2c f 2d). Etherification of 2d
with 4-vinylbenzyl chloride yields H1.
tion compared to their analogues P1A-P2A but show
the same shape of the curve. The ratio between the
absorption intensities of both types of polymers corre-
sponds to the expected ratio, which results from the
different monomer feed ratios. Furthermore, the nitro-
gen content was determined to verify the copolymeri-
zation ratios, and the values are in accordance with the
calculated contents and calculated from the ratio be-
The monomers H2, H3, and H4 were synthesized
starting from the corresponding secondary amines 3a
and 4a, which were coupled with 4,4′-dibromobiphenyl
yielding 3b and 4b. A sequence of two further coupling
steps, first with primary aromatic amines, yielding 3c,
4c, and 5c and second between the secondary amines
and protected 4-bromobenzyl alcohol, followed by a
deprotection step yields 3d, 4d, and 5d. Finally, H2,
H3, and H4 were obtained by introducing the unsatur-
ated carbon function via etherification with 4-vinylben-
zyl chloride.
1
tween H NMR integrals of the oxymethylene groups
of cross-linker (δ ) 3.4) and all oxymethylene groups (δ
) 3.4 and 4.4)
The mobility of the oxetane groups is important to
achieve complete cross-linking of the polymer layers. As
a consequence, the polymers should show a glass
transition temperature (Tg) below the curing tempera-
ture of the film after UV irradiation. The Tg’s were
measured by differential scanning calorimetry (DSC).
All polymers show a Tg below the used minimum curing
temperature of 100 °C.
Polymer Synthesis and Characterization. Co-
polymers of styrene-functionalized hole transporters
(H1, H2, H3, H4) and a styrene-functionalized oxetane
(C1) were synthesized by standard free-radical solution
polymerization methods with AIBN as initiator (Scheme
3). Copolymers with two different monomer ratios were
synthesized in order to investigate the influence of
oxetane content on cross-linking properties on one hand
and charge transporting performance on the other hand.
Polymers (P1B-P4B) with a molar ratio H1(or H2, H3,
H4)/C1 ) 3:1 seem to be good hole transporters but may
show incomplete cross-linking, whereas polymers (P1A-
P4A) with the ratio 1:1 show complete cross-linking but
may have weaker charge-transporting properties.
Molecular weights and polydispersity indices (PDIs)
of the polymers were determined by gel permeation
chromatography (GPC) with a light scattering (LS)
detector at λ ) 690 nm, using chloroform as solvent
(Table 1). UV-vis absorption and fluorescence spectra
were recorded to evaluate the optical properties of the
copolymers. Due to their higher contents of hole-
transporting groups, P1B-P4B show increased absorp-
The free-radical polymerization process leads to a
relatively broad molecular-weight distribution of the
polymers (PDI > 2). Regarding the potential application,
this does not constitute a disadvantage since the
polymer layer is cross-linked after application onto a
substrate anyway. Nevertheless, the molecular weight
must be sufficiently high to enable sufficient film-
forming capabilities and to ensure that every polymer
chain bears at least two oxetane units which partici-
pates in the cross-linking process. For a molecular
weight of 10.000 g/mol, each chain contains on average
about 8-9 oxetane units.
Cross-Linking. Cross-linking of films of P1-P4
proceeds via cationic polymerization, which is commonly
used for oxetanes.19,20 The commercially available pho-
toinitiator 6 (PI; Scheme 4) was added to initiate the

Macromolecules, Vol. 38, No. 5, 2005
Photo-Cross-Linkable Hole-Conducting Polymers 1643
Scheme 4. Chemical Structures of the Low-Molecular-Weight Hole Conductor OTPD22,23 Used as Reference
Material and Iodonium Photoinitiator 6 (PI)
cross-linking process. During ultraviolet (UV) illumina-
tion, this photoacid decomposes via a multiple-step
mechanism and generates protons, which open the
oxetane ring and start the polymerization. First, we
investigated the optimal conditions for cross-linking in
order to obtain complete solvent resistivity (SR; see
Experimental Section for details). We found that for PI
contents below 5 wt% complete SR could not be achieved
at room temperature. This is attributed to the fact that
the viscosity of a film increases dramatically during the
polymerization, such that the diffusional motion of the
oxetane units is strongly hindered. Thus, the reaction
stops for mechanical reasons; however, the chain ends
(carbocations) are still intact. Under these conditions,
however, the films are often still partly soluble. Curing
at an elevated temperature softens the films such that
the cross-linking reaction can proceed further, leading
in the ideal case to complete insolubility. The progress
of cross-linking was also studied by Fourier transform
infrared (FTIR) spectroscopy.
Electrochemical Characterization. The redox
chemical properties of the cross-linked films were
investigated by cyclic voltammetry. In analogy to low-
molecular-weight triarylamines,21 it was possible to
reversibly convert the triarylamine groups of the poly-
mers first to a radical cation then to a dication in all
four cases. A typical example is shown in Figure 3 for
the polymer P3A; we found no changes in electrical
performance of the material during 10 cycles, an im-
portant prerequisite for application as hole conductor
in OLEDs. Table 2 lists the oxidation potentials for P1-
P4. In each case, the identical potentials were obtained
for the A- and the B-series, respectively.
It is worth mentioning that the cationic form of the
hole-transport polymer is soluble in acetonitrile; there-
fore, film degradation of the un-cross-linked polymer
takes place which can also be recognized in a weak
reduction curve. This drawback can be avoided com-
Figure 2 shows the SR of 100 nm thick film of the
polymers P3A and P3B with different ratios of the hole-
transport monomer and the cross-linkable monomer.
Similar results were obtained for the other three
polymers. The dependence on the PI content for constant
curing temperature (here, T ) 100 °C) clearly shows
that the SR increases as the PI content increases and
then levels for c(PI) > 2 wt%, i.e., increasing the PI
content beyond this does not lead to an improved SR.
Furthermore, it is obvious that the polymer P3A is more
easily cross-linked than P3B, which is expected due to
the higher density of oxetane units.
Figure 2. Cyclic voltammograms of a cross-linked film of P3A
in a 0.05 M solution of Bu4NPF6 in acetonitrile. We show the
first and the tenth cycle.
Figure 1. Dependence of the solvent resistivity (SR) of the
polymers P3A (solid circles) and P3B (open circles) on the PI
content at a curing temperature of 100 °C (a) and the curing
temperature, T, at PI ) 1 wt% (b). The lines are guides to the
eye.
When the curing temperature is varied for a constant
PI content (here, 1 wt%) we found a higher curing
temperature led to significantly improved SR. The lower
the curing temperature, the larger the difference in SR
between the two types of polymers. The gap becomes
smaller, and ultimately for the highest curing temper-
atures (T > 150 °C), SR ) 100% could be achieved in
all cases.
Figure 3. Field dependence of the current in hole-only devices
ITO/PnA/Ag (150 nm) made of OTPD (squares) P1A (circles),
P2A (up triangles), P3A (down triangles), and P4A (dia-
monds). The initiator concentration was 1 wt%; curing was
performed at 150 °C for 60 s. The lines are guides to the eye.

1644 Bacher et al.
Table 2. Redox Potentials of P1-P4 Relative to
Macromolecules, Vol. 38, No. 5, 2005
Waters), and a Wyatt miniDAWN light-scattering detector (λ
) 690 nm) on samples in CHCl3. All samples were filtered
through a 0.22 µm Teflon filter (Millipore) to remove solid
particles. UV-vis spectra were recorded on a Varian Cary 3
spectrophotometer in the range 280-500 nm. Elemental
analyses (C, H, N) were performed on a Elementar Vario EL
analyzer. NMR data were obtained on a Bruker ARX 300 at
300.13 MHz (1H) and 75.48 MHz (13C) and are listed in parts
per million (ppm) downfield from tetramethylsilane for proton
and carbon. Abbreviations for aromatic C and H atoms are:
bz ) benzyl, dphe ) diphenylene, mph ) 4-methylphenyl, na
) 1-naphthyl, ox ) oxetane, ph ) phenyl, phe ) phenylene,
and vbz ) 4-vinylbenzyl; o, m, and p stand for ortho, meta,
and para relative to N or Br atoms. Coupling constants are
given in Hertz (Hz). FT-IR spectra (ATR spectra and KBr
spectra) were recorded on a Bruker IFS 55 spectrophotometer.
EI mass spectra were recorded by a Finnigan MAT 8200 mass
spectrometer. The monomers were dissolved in benzene for the
freeze-drying procedure. The resulting solution was frozen with
liquid nitrogen and then allowed to slowly reach room tem-
perature in a vacuum.
Ferrocene
P1
P2
P3
P4
potential for P/P+ (mV)
potential for P+/P2+ (mV)
241
643
455
553
490
610
479
584
pletely by cross-linking the polymer before the electro-
chemical experiments (see Experimental Section). After
cross-linking, the films are perfectly stable during
cyclovoltammetry.
The differences in the redox potentials for the four
transport units is in perfect agreement with the low-
molecular-weight analogues. The first oxidation P1/P1+•
takes place at a low potential compared to P2/P2+•,
whereas the potential of the second oxidation P1+•/P12+
is higher compared to P2+•/P22+. This is due to different
electronic coupling between the charge-bearing subunits
(N atoms); the reduction of the intramolecular distance
(biphenyl (P2) f benzene (P1)) leads to a higher
splitting of the half-wave oxidation potentials.21 The
naphthyl group lowers the electron density at the
nitrogen compared to phenyl; therefore, oxidation of P3
is only possible at higher potentials compared to those
of P2. The values for P4 lie between P2 and P3 as
expected.
Hole-Only Devices. Hole-only devices were prepared
to characterize the transport properties of the novel
polymers. The current-voltage diagrams are shown in
Figure 3. All polymers show significantly higher onset
voltages than the low-molecular-weight reference OTPD.
One possible explanation for this finding could be
differences in the ratio between active (i.e., hole conduc-
tive) and inactive (alkyl spacers and oxetane) units. In
the 1:1 polymers (A-series), the inactive units account
for about 35% of the repeat unit, while in OTPD, about
25% of the molar mass is inactive. Additionally, the
relative orientation of the triarylamine units might be
more favorable in OTPD.
3-Ethyl-3-(6-hydroxyhexyl)oxymethyl-oxetane 1b. So-
dium hydride (2.88 g, 120 mmol) was suspended in 200 mL of
dimethylformamide (DMF) under N2 atmosphere. 1,6-Hex-
anediol (47.3 g, 400 mmol), dissolved in 200 mL of DMF, was
added to the suspension. After being degassed and saturated
with N2, the mixture was stirred at 50 °C until the H2 evolu-
tion had ceased (ca. 1 h). 3-Chloromethyl-3-ethyloxetane 1a
(13.5 g, 100 mmol) was added, and the mixture was stirred at
90 °C for 16 h. After being cooled to room temperature, the
solvent was removed in a vacuum, the residue was dissolved
in 300 mL of diethyl ether and was washed three times with
200 mL of water. The organic layer was dried over MgSO4,
and the solvent was evaporated. The crude product was
purified by distillation in a glass oven at 170-180 °C/0.3 hPa
to give a clear, colorless liquid (13.2 g, 61%). C12H24O3 (216.32
g/mol). Anal. Calcd (%): C, 66.63; H, 11.18. Found (%): C,
65.23; H, 10.89. 1H NMR (CDCl3) δ: 4.38 (d, 2H, 2JH,H ) 5.73
Hz, H-ox); 4.30 (d, 2H, 2JH,H ) 5.73 Hz, H-ox); 3.57 (t, 2H, 3JH,H
) 6.30 Hz, -CH2-O-); 3.45 (s, 2H, -O-CH2-); 3.39 (t, 2H,
3
3JH,H ) 6.51 Hz, -CH2-OH); 1.67 (q, 2H, JH,H ) 7.62 Hz,
H3C-CH2-); 1.51 (m, 4H, -CH2-); 1.32 (m, 4H, -CH2-); 0.82
(t, 3H, JH,H ) 7.44 Hz, -CH3). 13C NMR (CDCl3) δ:
3
78.9 (-CH2-, ox); 73.8 (-CH2-O-); 71.9 (-O-CH2-); 63.3
(-CH2-OH); 43.8 (C, ox); 33.1, 29.9, 27.2, 26.4 (-CH2-); 26.0
(CH3-CH2-); 8.6 (CH3-).
Conclusion
In conclusion, a variety of cross-linkable polymers
suitable as hole transporters were synthesized and
characterized. The cross-linked films show high me-
chanical stability, as well as fully reversible electro-
chemical characteristics. Concerning the cross-linkabil-
ity and oxidation potentials, these polymers meet the
requirements of a hole-transport layer in OLEDs. Hole-
only devices made from the novel materials exhibited
higher onset voltages than low-molecular-weight cross-
linkable analogues. The concept of styrene-based func-
tional materials is very versatile and allows us to
synthesize other polymers with optimized hole conduc-
tor/cross-linker ratios for optimization of onset voltage.
3-Ethyl-3-(6-((4-vinylphenyl)methyl)oxyhexyl)-
oxymethyloxetane C1. Sodium hydride (1.44 g, 60.0 mmol)
was suspended in 130 mL of DMF under N2 atmosphere.
3-Ethyl-3-(6-hydroxy-1-hexyl)oxyoxetane 1b (10.8 g, 50.0 mmol)
was added to the suspension. After being degassed and
saturated with N2, the mixture was stirred at 50 °C until the
H2 evolution had ceased (ca. 1 h). 4-Vinylbenzyl chloride (8.39
g, 55.0 mmol) was added, and the mixture was stirred at 90
°C for 16 h. After being cooled to room temperature, the solvent
was removed in vacuo, and the residue was dissolved in 200
mL of diethyl ether and washed twice with 100 mL of water.
The organic layer was dried over MgSO4, and the solvent was
evaporated. The crude product was purified by column chro-
matography (80 mm diameter, 25 cm length, silica gel, ethyl
acetate/cyclohexane v/v 1.5:1) to give a clear, bright yellow
liquid (10.8 g, 65%). C21H32O3 (332.48 g/mol). Anal. Calcd (%):
C, 75.86; H, 9.70. Found (%): C, 75.09; H, 9.51. 1H NMR
Experimental Section
General Details. All synthesis steps were carried out under
nitrogen using standard Schlenk techniques. Toluene, diethyl
ether, and tetrahydrofuran were distilled from sodium under
nitrogen. Cyclohexane, toluene, and ethyl acetate for column
chromatography were distilled from technical grade solvents
and recycled after use. All other chemicals were reagent grade
and used as received (ABCR, Aldrich, Merck, Strem) without
further purification. If necessary, the products were purified
by column chromatography with silica gel (Fluka, KG 60,
0.063-0.2 mm).
3
(CDCl3) δ: 7.37 (d, 2H, JH,H ) 8.01 Hz, H-phe); 7.27 (d, 2H,
3JH,H ) 8.01 Hz, H-phe); 6.69 (dd, 1H, 3JH,H ) 17.53 Hz, 3JH,H
) 10.86 Hz, -CHdCH2); 5.72 (dd, 1H, 3JH,H ) 17.53 Hz, 2JH,H
3
2
) 0.78 Hz, -CHdCH2); 5.21 (dd, 1H, JH,H ) 10.87 Hz, JH,H
) 0.78 Hz, -CHdCH2); 4.47 (s, 2H, -CH2-O-); 4.42 (d, 2H,
2
2JH,H ) 5.91 Hz, H-ox); 4.35 (d, 2H, JH,H ) 5.91 Hz, H-ox);
3
3.50 (s, 2H, -O-CH2-); 3.44 (t, 2H, JH,H ) 6.66 Hz, -O-
3
CH2-); 3.42 (t, 2H, JH,H ) 6.48 Hz, -CH2-O-); 1.72 (q, 2H,
3JH,H ) 7.44 Hz, -CH2-CH3); 1.58 (m, 4H, -CH2-); 1.36
3
Gel permeation chromatography (GPC) with light-scattering
detection was carried out using a Styragel HR 4E column, a
2414 differential refractometer, a 484 UV detector (all from
(m, 4H, -CH2-); 0.86 (t, 3H, JH,H ) 7.42 Hz, -CH2-CH3).
13C NMR (CDCl3) δ: 138.7, 137.3 (C, phe); 137.0 (C, vinyl);
128.2, 126.6, 114.0 (C, phe); 79.0 (-CH2-, ox); 73.8, 73.0, 71.9,

Macromolecules, Vol. 38, No. 5, 2005
Photo-Cross-Linkable Hole-Conducting Polymers 1645
70.7 (-CH2-O-); 43.8 (C, ox); 30.1, 29.9, 27.1, 26.4, 26.4
(-CH2-); 8.6 (-CH3).
ferrocene (111 mg, 0,200 mmol) were dissolved under N2
atmosphere in 150 mL of dry toluene. After being stirred for
10 min at room temperature to form the catalytic system, the
bromoarene (2b, 6.48 g; 3b, 8.01 g; 4b, 9.01 g; 20.0 mmol),
arylamine (aniline, 4.66 g; 1-naphthylamine, 7.16 g; 50.0
mmol), and sodium tert-butoxide (2.31 g, 24.0 mmol) were
added to the solution. The solution was degassed and saturated
with N2 before being stirred at 100 °C for 6 h. After being
cooled to room temperature, the reaction mixture was diluted
with 100 mL of toluene and washed twice with 150 mL of
water. The toluene layer was dried over MgSO4, and the
solution was concentrated to give a colored oil. The crude
product was purified by column chromatography (80 mm
diameter, 25 cm length, silica gel, toluene/cyclohexane, v/v 2:1)
to give a clear, colored oil (2c) which crystallized after 2 days
to a white or yellow solid (2c, 5.45 g, 81%; 3c, 6.93 g, 84%; 4c,
9.43 g, 92%; 5c, 8.33 g, 90%;).
N,N,N′-Triphenyl-p-phenylenediamine 2c. C24H20N2
(336.44 g/mol). Anal. Calcd (%): C, 85.68; H, 5.99; N, 8.33.
Found (%): C, 85.76; H, 5.99; N, 8.13. 1H NMR (CDCl3) δ:
7.28-7.21 (m, 6H, H-ph m N); 7.12-7.05 (m, 6H, H-ph o N);
7.03-6.92 (m, 7H, H-ph p N, H-phe). 13C NMR (CDCl3) δ:
147.9; 143.1; 141.2; 137.6; 129.9; 129.4; 123.1; 122.4; 121.6;
118.9; 118.0; 117.9.
N,N,N′-Triphenylbenzidine 3c. C30H24N2 (412.54 g/mol).
Anal. Calcd (%): C, 87.34; H, 5.86; N, 6.79. Found (%): C,
87.26; H, 5.98; N, 6.60. 1H NMR (CDCl3) δ: 7.47-7.36 (m, 4H,
H-dphe m N); 7.30-7.20 (m, 6H, H-ph m N); 7.16-7.04 (m,
10H, H-ph o N, H-dphe o N); 7.04-6.96 (m, 3H, H-ph p N).
13C NMR (CDCl3) δ: 149.2; 147.6; 145.0; 144.2; 136.6; 133.4;
130.3; 130.1; 128.2; 128.0; 125.6; 125.2; 123.7; 121.2; 118.5;
118.4.
N-Phenyl-N,N′-dinaphthylbenzidine 4c. C38H28N2 (512.66
g/mol). Anal. Calcd (%): C, 89.03; H, 5.51; N, 5.46. Found (%):
C, 89.13; H, 5.59; N, 5.02. 1H NMR (CDCl3) δ: 8.05-7.84 (m,
4H, H-na o/m N); 7.78-7.73 (m, 1H, H-na p N); 7.59-7.56 (m,
1H, H-na p N); 7.51-7.32 (m, 8H, H-na); 7.27-7.15 (m, 6H,
H-ph m N, H-dphe m N); 7.06-7.00 (m, 6H, H-ph o N, H-dphe
o N); 6.95-6.90 (m, 1H, H-ph p N); 2.35 (s, 1H, N-H). 13C
NMR (CDCl3) δ: 148.4; 147.4; 147.2; 143.5; 135.3; 134.7; 134.0;
134.5; 134.4; 131.3; 129.1; 129.0; 128.6; 128.4; 128.2; 127.6;
127.4; 127.3; 127.1; 126.5; 126.4; 126.3; 126.2 126.1; 126.0;
125.8; 125.3; 124.3; 122.0; 121.9; 121.8; 121.7; 117.9; 116.4.
N,N′-Diphenyl-N-naphthylbenzidine 5c. C34H26N2 (462.60
g/mol). Anal. Calcd (%): C, 88.28; H, 5.67; N, 6.06. Found (%):
C, 88.57; H, 5.75; N, 5.81. 1H NMR (CDCl3) δ: 8.04-7.82 (m,
2H, H-na o/m N); 7.59-7.56 (m, 1H, H-na p N); 7.53-7.47 (m,
4H, H-na); 7.47-7.36 (m, 4H, H-dphe m N); 7.30-7.20 (m, 4H,
H-ph m N); 7.16-7.04 (m, 8H, H-ph o N, H-dphe o N); 7.04-
6.96 (m, 2H, H-ph p N). 13C NMR (CDCl3) δ: 149.2; 147.6;
145.0; 144.2; 136.6; 133.4; 130.3; 130.1; 128.2; 128.0; 125.6;
125.2; 123.7; 121.2; 118.5; 118.4.
tert-Butyldimethylsilyl-(4-bromobenzyl) Ether. 4-Bro-
mobenzyl alcohol (9.35 g, 50.0 mmol) was dissolved in 120 mL
of dichloromethane. After addition of tert-butyldimethylsilyl
chloride (7.84 g, 52.0 mmol), the solution was chilled down to
0 °C. Then, pyridine (4.75 g, 60.0 mmol) was added dropwise
within 15 min before stirring further for 10 min. After the ice
bath was removed, the reaction mixture was stirred at room
temperatur for 5 h. The mixture was washed twice each with
100 mL of 5% HClaq and dried over MgSO4. After the solvent
was removed in vacuo, the crude product was distilled at 140-
150 °C/0.1 hPa in a glass oven to give a colorless liquid (14.5
g, 96%). C13H21OSiBr (301.30 g/mol). Anal. Calcd (%): C, 51.82;
H, 7.03; Si, 9.32; Br, 26.52. Found (%): C, 49.45; H, 6.57; Si,
8.65; Br, 26.76. 1H NMR (CDCl3) δ: 7.44 (dm, 2H, 3JH,H ) 8.40
Hz, H-phe o Br); 7.19 (dm, 2H, 3JH,H ) 8.40 Hz, H-phe m Br);
4.66 (s, 2H, phe-CH2-O); 0.90 (s, 9H, -C(CH3)3); 0.10 (s, 6H,
-Si(CH3)2-C). 13C NMR (CDCl3) δ: 140.8; 131.7; 128.1; 121.0;
64.7; 26.3; -3.5; -5.2.
N,N-Diphenyl-4-bromoaniline 2b. Triphenylamine 2a
(29.4 g, 120 mmol) and NBS (21.4 g, 120 mmol) were dissolved
in 500 mL of carbon tetrachloride. The solution was refluxed
for 4 h. The precipitated succinimide was filtered, and the
solvent was evaporated from the solution. The remaining gray
oil was recrystallized from ethanol. The obtained white
crystalline powder (36,2 g, 93%) was dried in a vacuum. C18H14-
NBr (324.22 g/mol). Anal. Calcd (%): C, 66.68; H, 4.35; N, 4.42;
Br, 24.64. Found (%): C, 66.63; H, 4.39; N, 4.36; Br, 24.27. 1H
NMR (CDCl3) δ: 7.35-7.20 (m, 6H, H-ph m N, H-phe m N);
7.11-6.99 (m, 6H, H-ph o N, H-phe o N); 6.97-6.90 (m, 2H,
H-ph p N). 13C NMR (CDCl3) δ: 147.4; 147.0; 132.1; 129.4;
125.1; 124.4; 123.2; 114.8.
General Procedure for the Synthesis of 4-(N,N-Dia-
rylamino)-4′-bromobiphenyls 3b and 4b. Tris(dibenzylidene
acetone) dipalladium(0) (192 mg, 0.210 mmol) and bis(diphe-
nylphosphino) ferrocene (233 mg, 0.420 mmol) were dissolved
under N2 atmosphere in 250 mL of dry toluene. After being
stirred for 10 min at room temperature to form the catalytic
system, the diarylamine (3a, 5.08 g; 4a, 6.58 g; 30.0 mmol)
and 4,4′-dibromobiphenyl (31.2 g, 100.0 mmol) and sodium tert-
butoxide (3.46 g, 36.0 mmol) were added to the solution. The
mixture was degassed and saturated with N2 before being
stirred at 100 °C for 7 h. After being cooled to room temper-
ature, the reaction mixture was diluted with 100 mL of toluene
and washed twice with 150 mL of water. The toluene layer
was dried over MgSO4, and the solvent was removed in vacuo.
The crude product was isolated by column chromatography
(80 mm diameter, 25 cm length, silica gel) first with cyclohex-
ane as eluent to recover the dibromobiphenyl then with
toluene/cyclohexane v/v 1:1 to give the product as a white solid
(3b, 8.2 g, 68%; 4b, 10.5 g, 78%).
4-(N,N-Diphenylamino)-4′-bromobiphenyl 3b. C24H18-
NBr (400.32 g/mol). Anal. Calcd (%): C, 72.01; H, 4.53; N, 3.50;
Br, 19.96. Found (%): C, 72.39; H, 4.60; N, 3.61; Br, 19.52. 1H
NMR (CDCl3) δ: 7.54-7.49 (m, 2H, H-dphe o Br); 7.44-7.34
(m, 4H, H-dphe); 7.30-7.21 (m, 4H, H-ph m N); 7.15-7.08 (m,
General Procedure for the Synthesis of N,N,N′-Tri-
phenyl-N′-(4-(hydroxymethyl)phenyl)-p-phenylenedi-
amine 2d and N,N,N′-Triaryl-N′-(4-(hydroxymethyl)-
phenyl)benzidines 3d, 4d, and 5d. 1. C-N coupling.
Tris(dibenzylidene acetone) dipalladium(0) (91.6 mg, 0,100
mmol) and tri-tert-butylphosphane (122 mg, 0.600 mmol) were
dissolved under N2 in 130 mL of dry toluene. After being
stirred for 10 min at room temperature to form the catalytic
system, the arylamine, (2c, 6.73 g; 3c, 8.25 g; 4c, 10.25 g; 5c,
9.25 g; 20.0 mmol), tert-butyldimethylsilyl-(4-bromobenzyl)
ether (6.03 g, 20.0 mmol) and sodium tert-butoxide (2.31 g,
24.0 mmol) were added to the solution. The solution was
degassed and saturated with N2 before being stirred at 100
°C for 5 h. After being cooled to RT, the reaction mixture was
diluted with 100 mL of toluene and washed with 200 mL of a
saturated solution of sodium chloride. The organic phase was
dried over MgSO4, and the solvent was evaporated to give a
colored solid.
6H, H-ph o N, H-dphe o N); 7.07-7.00 (m, 2H, H-ph p N). 13
C
NMR (CDCl3) δ: 147.5; 139.6; 133.6; 131.8; 129.3; 128.2; 127.5;
124.6; 123.7; 123.1; 120.9.
4-(N-(1-Naphthyl)-N-phenylamino)-4′-bromobiphenyl
4b. C28H20NBr (450.38 g/mol). Anal. Calcd (%): C, 74.67; H,
4.48; N, 3.11; Br, 17.74. Found (%): C, 75.02; H, 4.48; N, 3.24;
Br, 17.43. 1H NMR (CDCl3) δ: 7.98-7.84 (m, 2H, H-na o/m
N); 7.81-7.72 (m, 1H, H-na p N); 7.52-7.42 (m, 4H, H-dphe o
Br, H-na); 7.41-7.28 (m, 6H, H-dphe, H-na); 7.25-7.13 (m,
2H, H-ph m N); 7.12-7.00 (m, 4H, H-ph o N, H-dphe o N);
7.00-6.92 (m, 1H, H-ph p N). 13C NMR (CDCl3) δ: 148.2;
148.0; 143.2; 139.6; 135.3; 132.6; 131.8; 131.2; 129.2; 128.4;
128.1; 127.4; 127.3; 126.7; 126.5; 126.4; 126.2; 124.2; 122.4;
122.2; 121.4; 120.7.
2. Deprotection. The product of the first synthetic step was
dissolved in 200 mL of THF. After the addition of 21.0 mL of
tetra-n-butylammonium fluoride solution (1.0 mol/L, contains
5% water), the solution was stirred for 2 h at RT. The solvent
was removed, and the product was purified by column chro-
General Procedure for the Synthesis of N,N,N′-Tri-
phenyl-p-phenylendiamine 2c and N,N,N′-Triarylben-
zidines 3c, 4c, and 5c. Tris(dibenzylidene acetone) dipalla-
dium(0) (91.6 mg, 0.100 mmol) and bis(diphenylphosphino)

1646 Bacher et al.
Macromolecules, Vol. 38, No. 5, 2005
matography (80 mm diameter, 25 cm length, silica gel, toluene/
ethyl acetate 2:1) to yield a weakly colored solid (2d, 7.26 g,
82%; 3d, 8.82 g, 85%; 4d, 11.0 g, 89%; 5d, 10.12 g, 89%).
N,N,N′-Triphenyl-N′-(4-(hydroxymethyl)phenyl)-p-phe-
nylene-diamine 2d. C31H26ON2 (442.56 g/mol). El. Anal.
Calcul. (%): C 84.13; H 5.92; N 6.33. found (%): C 83.79; H
5.86; N, 4.09. 1H NMR (CDCl3) δ: 7.47-7.29 (m, 8H, H-phe m
N, H-vbz); 7,28-7,17 (m, 8H, H-ph m N, H-dphe m N); 7.15-
7.05 (m, 12H, H-dphe o N, H-ph o N); 7.05-6.97 (m, 3H, H-ph
3
3
p N); 6.71 (dd, 1H, JHH ) 10,86 Hz, JHH ) 17,56 Hz, ph-
3
CHdCH2); 5.74 (d, 1H, JHH ) 17,56 Hz, ph-CHdCH2); 5.23
3
(d, 1H, JHH ) 10.86 Hz, ph-CHdCH2); 4.57/4.48 (s/s, 4H,
1
5.87; N 6.17. H NMR (CDCl3) δ 7.27-7.20 (m, 8H, H-ph m
-O-CH2-). 13C NMR (CDCl3) δ: 147.7; 147.6; 147.3; 146.8;
146.6; 137.9; 137.0; 136.6; 134.8; 134.7; 132.5; 129.2; 129.1;
128.0; 127.3; 126.3; 124.3; 124.1; 124.0; 122.9; 122.8; 113.8;
71.9; 71.8. EI-MS m/z (%): 634.4 (M+•, 100); 501.2 (65).
N,N′-Dinaphthyl-N-phenyl-N′-(4-((4-vinylphenyl)-
methoxymethyl)phenyl)benzidine H4. C54H42ON2 (734,94
g/mol). Anal. Calcd (%): C, 88.25; H, 5.76; N, 3.81. Found (%):
C, 88.02; H, 5.76; N, 3.49. 1H NMR (CDCl3) δ: 7.97-7.81 (m,
4H, H-na o/m N); 7.79-7.70 (m, 2H, H-na p N); 7.50-7.26 (m,
16H, H-dphe m N, H-na, H-vbz); 7.25-7.10 (m, 4H, H-ph m
N, H-dphe m N); 7.09-6.97 (m, 8H, H-ph o N, H-dphe o N);
N); 7.11-7.05 (m, 8H, H-ph o N); 7.01-6.92 (m, 7H, H-ph p
N, H-phe). 13C NMR (CDCl3) δ 147.8; 147.5; 143.0, 142.7; 134.7;
129.2; 128.3; 125.5; 125.4; 123.8; 123.6; 122.5; 122.4; 65.1. EI-
MS m/z (%): 441.8 (M+•, 100); 220.9 (M2+, 19).
N,N,N′-triphenyl-N′-(4-(hydroxymethyl)phenyl)benzi-
dine 3d. C37H30ON2 (518.70 g/mol). Anal. Calcd (%): C, 85.68;
H, 5.83; N, 5.40. Found (%): C, 85.15; H, 6.00; N, 5.13. 1H
NMR (CDCl3) δ: 7.47-7.35 (m, 4H, H-dphe m N); 7.29-7.19
(m, 8H, H-ph m N); 7.15-7.05 (m, 12H, H-dphe o N, H-ph o
N); 7.04-6.96 (m, 3H, H-ph p N). 13C NMR (CDCl3) δ: 147.7;
147.6; 147.3; 146.8; 146.6; 135.2; 134.9; 134.7; 129.3; 129.2;
128.3; 127.3; 124.4; 124.3; 124.2; 124.0; 123.0; 122.8; 65.1. m/z
(%): 517.9 (M+•, 100); 258.9 (M2+, 30).
3
6.96-6.89 (m, 1H, H-ph p N); 6.71 (dd, 1H, JHH ) 10,89 Hz,
3JHH ) 17,74 Hz, ph-CHdCH2); 5.74 (d, 1H, 3JHH ) 17.74 Hz,
3
ph-CHdCH2); 5.23 (d, 1H, JHH ) 10.89 Hz, ph-CHdCH2);
N,N′-Dinaphthyl-N-phenyl-N′-(4-(hydroxymethyl)phe-
nyl)benzidine 4d. C45H34ON2 (618.78 g/mol). Anal. Calcd
(%): C, 87.35; H, 5.54; N, 4.53. Found (%): C, 86.86; H, 5.79;
4.54/4.45 (s/s, 4H, -O-CH2-). 13C NMR (CDCl3) δ: 148.3;
147.9; 147.3; 147.2; 145.6; 143.4; 138.0; 137.0; 136.6; 135.3;
133.9; 133.8; 131.4; 131.3; 131.2; 129.1; 129.0; 128.4; 128.2;
128.0; 127.2; 127.1; 126.5-126.3; 126.2; 126.1; 125.3; 124.3;
1
N, 4.05. H NMR (CDCl3) δ: 7.97-7.81 (m, 4H, H-na o/m N);
7.79-7.70 (m, 2H, H-na p N); 7.50-7.26 (m, 12H, H-dphe m
N, H-na); 7.25-7.12 (m, 4H, H-ph m N, H-bz m N); 7.09-6.97
(m, 8H, H-ph o N, H-dphe o N, H-bz o N); 6.96-6.89 (m, 1H,
H-ph p N); 4,59 (s, 2H, phe-CH2-OH). 13C NMR (CDCl3) δ:
148.3; 148.0; 147.3; 147.1; 143.5; 143.3; 135.3; 134.1; 134.0;
133.8; 131.3; 131.2; 129.1; 129.0; 128.4; 128.3; 127.2; 127.1;
126.6; 126.5; 126.4; 126.3; 126.2, 126.1; 125.3; 124.3; 124.2;
122.0; 121.9; 121.7; 113.7; 71.8. EI-MS m/z (%): 734.1 (M+•
,
100); 600.9 (38); 366.9 (M2+, 9).
N-Naphthyl,N,N′-diphenyl-N′-(4-((4-vinylphenyl)-
methoxymethyl)phenyl)benzidine H5. C50H40ON2 (684.88
g/mol). Anal. Calcd (%): C, 87.69; H, 5.89; N, 4.09. Found (%):
C, 88.01; H, 5.84; N, 3.85. 1H NMR (CDCl3) δ: 7.98-7.84 (m,
2H, H-na o/m N); 7.79-7.74 (m, 1H, H-na p N); 7.50-7.28 (m,
12H, H-dphe m N, H-vbz, H-na); 7.28-7.13 (m, 6H, H-ph m
N, H-bz m N); 7.13-7.02 (m, 10H, H-ph o N, H-dphe o N, H-bz
o N); 7.02-6.90 (m, 2H, H-ph p N); 6.71 (dd, 1H, 3JHH ) 10.87
Hz, 3JHH ) 17.73 Hz, ph-CHdCH2); 5.73 (d, 1H, 3JHH ) 17.73
122.1; 122.0; 121.9; 121.8; 65.2. EI-MS m/z (%): 617.9 (M+•
,
100); 309.0 (M2+, 14).
N-Naphthyl-N,N′-diphenyl-N′-(4-(hydroxymethyl)phe-
nyl)benzidine 5d. C41H32ON2 (568.72 g/mol). Anal. Calcd
(%): C, 86.59; H, 5.67; N, 4.93. Found (%): C, 86.30; H, 5.66;
3
Hz, ph-CHdCH2); 5.22 (d, 1H, JHH ) 10.87 Hz, ph-CHd
N, 4.46. H NMR (CDCl3) δ: 7.98-7.84 (m, 2H, H-na o/m N);
CH2); 4.57/4.48 (s/s, 4H, -CH2-O-). 13C NMR (CDCl3) δ:
148.3; 147.7; 147.4; 147.3; 146.5; 143.4; 137.9; 137.0; 136.6;
135.3; 134.9; 133.7; 132.5; 131.2; 129.2; 129.1; 129.0; 128.4;
128.2; 128.0; 127.3; 127.2; 126.5; 126.4; 126.3; 126.2; 126.1;
124.3; 124.2; 124.0; 122.8; 122.0; 121.8; 113.8; 71.9; 71.8. EI-
MS m/z (%): 683.9 (M+•, 100); 540.9 (40); 341.9 (M2+, 6).
Synthesis of Polymers P1A/B-P4A/B. The procedure
described for P1A is generally applicable to all other poly-
merizations. C1 (332 mg, 1.00 mmol) and H2 (559 mg, 1.00
mmol) were dissolved in 4 mL of toluene. After degassing of
the mixture and saturation with N2, R,R′-azo-bis(isobutyroni-
trile) (4.00 mg, 2 mg/mmol monomer) was added and the
solution was stirred 24 h at 80 °C. The mixture was diluted
with 3 mL of toluene, and the polymer was precipitated by
rapid injection of the solution into 200 mL of methanol. The
polymer was collected by filtration and dried in vacuo to yield
a white solid (820 mg, 92%). The crude polymer was redis-
solved in 6 mL of CHCl3 and precipitated again as described
above before using it for the experiments and analytics. Anal.
Calcd P1A (%): C, 82.2; H, 7.5; N, 3.1. Found (%): C, 82.0; H,
7.4; N, 3.1. Anal. Calcd P1B (%): C, 84.3; H, 5.1; N, 4.2. Found
(%): C, 84.3; H, 5.7; N, 4.1. Anal. Calcd P2A (%): C, 83.2; H,
7.3; N, 2.9. Found (%): C, 83.3; H, 7.1; N, 2.9. Anal. Calcd
P2B (%): C, 85.4; H, 6.6; N, 3.8. Found (%): C, 89.1; H, 6.6;
N, 3.8. Anal. Calcd P3A (%): C, 84.4; H, 7.0; N, 2.6. Found
(%): C, 84.9; H, 6.5; N, 2.6. Anal. Calcd P3B (%): C, 86.6; H,
6.3; N, 3.3. Found (%): C, 86.1; H, 6.2; N, 3.1. Anal. Calcd
P4A (%): C, 83.8; H, 7.1; N, 2.8. Found (%): C, 84.0; H, 6.7;
N, 2.7. Anal. Calcd P4B (%): C, 86.0; H, 6.4; N, 3.5. Found
(%): C, 85.9; H, 6.1; N, 3.5.
1
7.79-7.74 (m, 1H, H-na p N); 7.50-7.28 (m, 8H, H-dphe m N,
H-na); 7.28-7.13 (m, 6H, H-ph m N, H-bz m N); 7.13-7.02
(m, 10H, H-ph o N, H-dphe o N, H-bz o N); 7.02-6.90 (m, 2H,
H-ph p N); 4.59 (s, 2H, phe-CH2-OH). 13C NMR (CDCl3) δ:
148.3; 147.7; 147.4; 147.3; 146.5; 143.4; 137.0; 135.3; 134.9;
133.7; 131.3; 129.4; 129.1; 128.4; 128.2; 128.0; 127.3; 127.2;
126.5; 126.4; 126.3; 126.2; 124.3; 124.2; 124.0; 122.8; 122.0;
121.8; 71.9. EI-MS m/z (%): 567.9 (M+•, 100); 284.0 (M2+, 14).
General Procedure for Synthesis of the Monomers H2,
H3, H4, and H5. The hydroxymethyl-substituted arylamine
(2d, 4.43 g; 3d, 5.19 g; 4d, 6.19 g; 5d, 5.69 g; 10.0 mmol) was
dissolved in 100 mL of dry toluene under N2 atmosphere. After
addition of potassium (430 mg, 11.0 mmol), the reaction
mixture was stirred vigorously at 100 °C until the potassium
had dissolved completely and the H2 evolution had ceased
(about 3 h). 4-Vinylbenzyl chloride (1.83 g, 12.0 mmol) was
given to the cloudy suspension, which was then stirred at 90
°C for 20 h. The solution was diluted with 70 mL of toluene
and then washed with 150 mL of a saturated NaCl solution.
After evaporation of the solvent, the product was isolated by
column chromatography (80 mm diameter, 20 cm length, silica
gel, toluene/cyclohexane 3:1) to give a colorless glass. After
being freeze-dryed, a colorless product was yielded (H2, 3.30
g, 59%; H3, 3.49 g, 55%; H4, 4.41 g, 60%; H5, 4.18 g, 61%).
N,N,N′-Triphenyl-N′-(4-((4-vinylphenyl)methoxymeth-
yl)phenyl)-p-phenylenediamine H2. C40H34ON2 (558.73
g/mol). Anal. Calcd (%): C, 85.99; H, 6.13; N, 5.01. Found (%):
C, 85.63; H, 6.34; N, 4.79. 1H NMR (CDCl3) δ: 7.40-6.95 (m,
3
3
27H, H-arom); 6.73 (dd, 1H, JHH ) 10.86 Hz, JHH ) 17.73
3
Hz, ph-CHdCH2); 5.76 (d, 1H, JHH ) 17.73 Hz, ph-CHd
Cross-Linking Procedure. Commercially available mi-
croscope glass slides were used as the substrates. They were
carefully cleaned and dried before use. Solutions of the
polymers P1A/B-P4A/B in tetrahydrofuran/toluene(v/v ) 1:1)
solution were prepared, and varying amounts of the photoini-
tiator 6 were added shortly before spincoating, yielding films
of about 100-nm thickness. After spin-coating, the films were
irradiated with a UV lamp (λ ) 365 nm) for 10 s. To promote
cross-linking, the films were cured at temperatures varying
3
CH2); 5.24 (d, 1H, JHH ) 10.86 Hz, ph-CHdCH2); 4.55 (s,
4H, -O-CH2-). 13C NMR (CDCl3) δ: 141.6; 140.7; 136.4;
136.0; 135.8; 134.0; 131.6; 129.4; 128.5; 127.5; 126.1; 122.9;
122.4; 112.3; 69.4; 66.0. EI-MS m/z (%): 558.4 (M+•, 100); 425.2
(63).
N,N,N′-Triphenyl,N′-(4-((4-vinylphenyl)methoxymeth-
yl)phenyl)benzidine H3. C46H38ON2 (634.82 g/mol). Anal.
Calcd (%): C, 87.03; H, 6.03; N, 4.41. Found (%): C, 87.10; H,

Macromolecules, Vol. 38, No. 5, 2005
Photo-Cross-Linkable Hole-Conducting Polymers 1647
(2) Allen, N. S.; Khan, L.; Edge, M.; Billings, M.; Veres, J. J.
Photochem. Photobiol., A 1998, 116, 235-244.
from 25 °C (room temperature) to 150 °C for 1 min, respec-
tively. A UV-vis spectrum of the film was taken. To test the
solvent resistivity of the material, the film was then exposed
to THF, which is an excellent solvent for all polymers studied
here. We found that by simply rinsing the film with THF,
similar results as immersing the film into a THF bath with
applied ultrasound could be obtained. After this, another UV-
vis spectrum was recorded. The film resistivity was then
defined as the ratio of the peak absorption after and before
THF treatment. All steps were performed in inert gas atmo-
sphere and under red-light conditions.
(3) Yoshimoto, N.; Hanna, J.-I. J. Mater. Chem. 2003, 13, 1004-
1010.
(4) Bozano, L. D.; Carter, K. R.; Lee, V. Y.; Miller, R. D.; DiPietro,
R.; Scott, J. C. J. Appl. Phys. 2003, 94, 3061-3068.
(5) Contoret, A. E. A.; Farrar, S. R.; Khan, S. M.; O’Neill, M.;
Richards, G. J.; Aldred, M. P.; Kelly, S. M. J. Appl. Phys.
2003, 93, 1465-1467.
(6) Yoshimoto, N.; Hanna, J.-I. Adv. Mater. 2002, 14, 988-991.
(7) Zhang, Y.-D.; Hreha, R. D.; Jabbour, G. E.; Kippelen, B.;
Peyghambarian, N.; Marder, S. R. J. Mater. Chem. 2002, 12,
1703-1708.
Electrochemical Measurements. Cyclic voltammetry
(CV) was processed on a Gamry PC4/300 PC built-in poten-
tiostat with a three-electrode cell in a solution of Bu4NBF4
(0.05 M) in acetonitrile at scan rates of 10-100 mV/s. The
polymer films were coated onto the working electrode, a Pt
wire of 1 mm diameter with a length of 10 mm, by dipping
the electrode into a solution of the polymer (20 g/L) and the
photoinitiator (1 mol% relating to oxetane groups) in THF.
After drying in air, the film was cross-linked by UV irradiation
(8) Le Barny, P.; Bouche, C.-M.; Facoetti, H.; Soyer, F.; Robin,
P. Proc. SPIE-Int. Soc. Opt. Eng. 1997, 3148, 160-169.
(9) Domercq, B.; Hreha, R. D.; Zhang, Y.-D.; Larribeau, N.;
Haddock, J. N.; Schultz, C.; Marder, S. R.; Kippelen, B. Chem.
Mater. 2003, 15, 1491-1496.
(10) Nuyken, O.; Bo¨hner, R.; Erdmann, C. Macromol. Symp. 1996,
107, 125-138.
(11) Braig, T.; Bayerl, M. S.; Nuyken, O.; Mu¨ller, D. C.; Gross,
(10 s) with a mercury low-pressure fluorescent lamp (λmax
)
M.; Meerholz, K. Polym. Mater. Sci. Eng. 1999, 80, 122-123.
366 nm) and tempering in air at 120 °C for 1 min. A Pt plate
of 100 mm2 was used as the counter electrode. A silver wire
coated with AgCl was used to form the reference electrode.
Ferrocene was used as a reference substance and was mea-
sured by dissolving it in the acetonitrile-based solution.
Device Preparation. ITO(indium tin oxide)-coated glass
substrates were commercially obtained from Merck display
glass (20 Ω/in.2) and carefully cleaned and dried before use.
The ITO was treated by an ozone plasma, which alters the
work function to about 5.4 eV. Hole-only devices were obtained
following the film deposition procedure outlined above. The
initiator content was 1 wt%, and the curing was performed at
150 °C for 1 min. The films were then rinsed with THF to
remove the soluble decomposition products of the PI, as well
as non-cross-linked material (e.g., decomposition products of
the PI). Finally, Ag (150 nm) is deposited by thermal vacuum
evaporator as the top electrode. The entire characterization
was performed in a glovebox under inert gas atmosphere.
(12) Braig, T.; Mu¨ller, D. C.; Gross, M.; Meerholz, K.; Nuyken, O.
Macromol. Rapid Commun. 2000, 21, 583-589.
(13) Bayerl, M. S.; Braig, T.; Nuyken, O.; Mu¨ller, D. C.; Gross,
M.; Meerholz, K. Macromol. Rapid Commun. 1999, 20, 224-
228.
(14) Campbell, T. W. J. Org. Chem. 1957, 22, 1029.
(15) Bodenbrenner, K.; Wegler, R. (Farbenfabrik Bayer AG), DE
1 021 858, 1960, Chem. Abstr. 1960; Vol. 54, p 4617.
(16) Guram, A. S.; Rennels, R. A.; Buchwald, S. L. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1348-1350.
(17) Louie, J.; Hartwig, J. F. Tetrahedron Lett. 1995, 36, 3609-
3612.
(18) Yamamoto, T.; Nishiyama, M.; Koie, Y. Tetrahedron Lett.
1998, 39, 2367-2370.
(19) Sasaki, H.; Crivello, J. V. J. Macromol. Sci., Pure Appl. Chem.
1992, A29, 915-930.
(20) Fouassier, J.-P. Photoinitiation, Photopolymerization and
Photocuring: Fundamentals and Application; Hanser Pub-
lishers: Munich, Vienna, New York, Cincinnati, 1995.
(21) Coropceanu, V.; Gruhn, N. E.; Barlow, S.; Lambert, C.;
Durivage, J. C.; Bill, T. G.; Noell, G.; Marder, S. R.; Bredas,
J.-L. J. Am. Chem. Soc. 2004, 126, 2727-2731.
(22) Nuyken, O.; Bacher, E.; Braig, T.; Faber, R.; Mielke, F.;
Rojahn, M.; Wiederhirn, V.; Meerholz, K.; Mu¨ller, D. Des.
Monom. Polym. 2002, 5, 195-210.
(23) Rojahn, M. Ph.D. Thesis, Technische Universita¨t Mu¨nchen,
2003.
(24) Schneider, M.; Hagen, J.; Haarer, D.; Mu¨llen, K. Adv. Mater.
2000, 12, 351.
Acknowledgment. Financial support provided by
the Bundesministerium fu¨r Bildung und Forschung
(BMBF) through Project No. 13N8214, the Deutsche
Forschungsgemeinschaft (DFG), and the Bavarian gov-
ernment (Promotionsstipendium for E.B.) is gratefully
acknowledged. We thank B. Lerche, L. Friebe, J.
Krause, and M. Barth (all TU Mu¨nchen) for technical
support.
References and Notes
(1) Tak, Y. H.; Vestweber, H.; Ba¨ssler, H.; Bleyer, A.; Stockmann,
R.; Ho¨rhold, H.-H. Chem. Phys. 1996, 212, 471-485.
MA048365H