Synthesis and properties of triphenylamine-based hydrazones with reactive vinyl groups

Article abstract of DOI:10.1016/j.dyepig.2012.03.010

Two triphenylamine-based hydrazones with reactive vinyl groups were synthesized and characterized. The optical, thermal, electrochemical and photoelectrical properties of the obtained compounds were studied. All the synthesized hydrazone monomers form gla

Full text of DOI:10.1016/j.dyepig.2012.03.010

Dyes and Pigments 95 (2012) 47e52
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Synthesis and properties of triphenylamine-based hydrazones with reactive vinyl
groups
,
a
b
V. Mimaite a, J.V. Grazulevicius a , J. Ostrauskaite , V. Jankauskas
*
a Department of Organic Technology, Kaunas University of Technology, Radvilenu pl. 19, LT-50254 Kaunas, Lithuania
b Department of Solid State Electronics, Vilnius University, Sauletekio Aleja 9, LT-2040, Vilnius, Lithuania
a r t i c l e i n f o
a b s t r a c t
Article history:
Two triphenylamine-based hydrazones with reactive vinyl groups were synthesized and characterized.
The optical, thermal, electrochemical and photoelectrical properties of the obtained compounds were
studied. All the synthesized hydrazone monomers form glasses with the glass transition temperatures
ranging from 52 ꢀC to 82 ꢀC. The electron photoemission spectra of the synthesized hydrazones were
recorded and ionization potentials of 5.22e5.29 eV were established. Room temperature hole-drift
mobilities in the amorphous film of hydrazone monomer having three vinyl groups established by
xerographic time-of-flight technique was found to be 3.5 ꢁ 10ꢂ3 cm2/V$s at an electric field of
6.4 ꢁ 105 cm2/V$s. Self-polymerization of the hydrazones bearing vinyl groups was demonstrated by
differential scanning calorimetry. Self-polymerization of monomers containing one and three vinyl
groups started at 151 ꢀC and 136 ꢀC, while maximum polymerization rates were observed at 209 ꢀC and
167 ꢀC respectively.
Received 5 December 2011
Received in revised form
6 March 2012
Accepted 11 March 2012
Available online 29 March 2012
Keywords:
Hydrazone
Triphenylamine
Vinyl group
Polymerization
Charge mobility
Methoxy group
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
reactive functional groups, including hydrazones were described
[13e18]. Most of the polymerizable hydrazones reported until now
Organic semiconductors are currently widely used in different
optoelectronic and electronic devices [1e5]. Aromatic hydrazones
are among the most effective organic hole-transporting materials
[6]. Due to relatively high hole-drift mobilities, the simplicity of
synthesis, good compatibility with inert polymer hosts hydrazones
are widely used in electrophotographic photoreceptors of copying
machines, laser printers, fax machines [7]. They also showed
promising performance as hole-transporting glass-forming mate-
rials in dye sensitized solar cells [8,9], as unimolecular half-
substractors for molecular processors [10], and as active media in
memory devices [11]. It is known efficient organic optoelectronic
devices can be obtained most often by building multilayer struc-
tures [12]. The main difficulty in the preparation of such devices by
solution processing is the solubility of the material which forms the
bottom layer onto which the top layer has to be cast, because most
organic semiconductors are soluble in the same solvents. One
approach that was employed to circumvent this problem is the
appliance of electroactive derivatives with reactive functional
groups, which could be converted into insoluble networks by cross-
linking reactions. Several series of electroactive materials with
contained reactive epoxy groups. They could be converted into
polymers either by polyaddition or cationic polymerization. In this
work we report on the synthesis of triphenylamine-based hydra-
zones with reactive vinyl groups and demonstrate the possibility of
their self-polymerization.
2. Experimental
2.1. Instrumentation
1H NMR spectra were taken on a Varian Unity Inova (300 Hz)
spectrometer. IR spectra were recorded with Perkin Elmer Spec-
trum GX II FT-IR System. Mass spectra were obtained on a Waters
ZQ 2000 mass spectrometer. UV and fluorescence (FL) spectra of
10ꢂ4 M solutions of the synthesized compounds were recorded in
quartz cells using a Perkin Elmer Lambda 35 spectrometer and
Hitachi MPF-4 spectrofluorophotometer respectively. Thermogra-
vimetric analysis (TGA) was performed on Mettler TGA/SDTA851e/
LF/1100 apparatus at a heating rate of 20 ꢀC/min under nitrogen
atmosphere. Differential scanning calorimetry (DSC) measure-
ments were performed on DSC Q 100 TA Instrument at a heating
rate of 10 ꢀC/min under nitrogen atmosphere. Cyclic voltammetry
(CV) measurements were carried out with a glassy carbon working
* Corresponding author. Tel.: þ370 37 300193; fax: þ370 37 300152.
E-mail address: juozas.grazulevicius@ktu.lt (J.V. Grazulevicius).
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2012.03.010

48
V. Mimaite et al. / Dyes and Pigments 95 (2012) 47e52
electrode in a three electrode cell. The measurements were
carried out in dry dichloromethane solution containing 0.1 M tet-
rabutylammonium perchlorate as electrolyte at room temperature
under nitrogen atmosphere. Each measurement was calibrated
with the standard ferrocene/ferrocenium (Fc/Fcþ). The ionization
potentials (Ip) of the films of the synthesized compounds measured
by the electron photoemission in air method as described previ-
ously [19]. The measurement method was, in principle, similar to
that demonstrated by Miyamoto et al. [20]. The samples for the
ionization potential measurements were prepared by dissolving
compounds in tetrahydrofuran and casting thin layers on Al plates,
oxychloride (Aldrich), tetrabutylammonium hydrogensulfate
(Aldrich), sodium acetate (Aldrich), potassium carbonate (Lachner),
anhydrous sodium sulfate (Penta), potassium hydroxide (Aldrich),
were purchased as reagent grade chemicals and used as received. 4-
Methoxy-N-(4-methoxyphenyl)-N-phenylamine (1) was synthe-
sized by Ullmann coupling reaction according to the procedures
outlined in the literature [23]. 4-(Bis(4-methoxyphenyl)amino)
benzaldehyde (2) and tris(4-formylphenyl)amine (3) were synthe-
sized bythemethod ofVilsmeierasdescribed intheliterature [23,24].
2.2.1. 4-(Bis(4-metoxyphenyl)amino)benzaldehyde N-
phenylhydrazone (4)
pre-coated with ca. 0.5 mm thick adhesive layer of the copolymer of
methylmethacrylate and methacrylic acid (MKM). The function of
this layer was not only to improve adhesion but also to eliminate
electron photoemission from Al. No photoemission was detected
from Al plate overcoated with MKM at illumination with up to
6.25 eV quanta energy light. In addition, the MKM layer is
conductive enough to avoid charge accumulation on it during
measurements. The samples were illuminated with mono-
chromatic light from the quartz monochromator with deuterium
lamp. The power of the incident light beam was (2e5) ꢁ 10ꢂ8 W.
The negative voltage of 300 V was supplied to the sample
substrate. The counter-electrode with the 4.5 mm ꢁ 15 mm slit for
illumination was placed at 8 mm distance from the sample surface.
The counter-electrode was connected to the input of the BK2-16
type electrometer, working in the open impute regime, for the
photocurrent measurement. The strong photocurrent of
10ꢂ15e10ꢂ12 A was flowing in the circuit under illumination. Hole-
drift mobility measurements were performed by a xerographic
time-of-flight (XTOF) method [21]. The samples for the charge
mobility measurements were prepared as described earlier [22].
Phenylhydrazine (1 ml, 10.4 mmol) was added to the solution of
aldehyde (2) (1.7 g, 5.2 mmol) in 10 ml of methanol. The reaction
mixture was refluxed at 65 ꢀC with stirring for ca. 0.5 h until no
aldehyde was left (TLC monitoring). After cooling, yellowish precip-
itate was filtered, washed with large amount of methanol and dried.
The yield of 4 was 1.9 g (85%).
IR (KBr), n
/cmꢂ1: 3319 (NeH), 3027, 3000 (ar. CeH), 2956, 2932,
2908 (alif. CeH), 2837 (OeCH3), 1599, 1505 (ar. C]C), 1296 (CeN),
1241 (CeOeC).
1H NMR (CDCl3),
d(ppm): 3.84 (s, 6H, OCH3), 3.85 (s, 1H, NH),
6.88 (d, 5H, J ¼ 9 Hz, Ar), 6.94 (d, 2H, J ¼ 9 Hz, Ar), 7.11 (d, 5H,
J ¼ 9.3 Hz, Ar), 7.17 (d, 1H, J ¼ 9 Hz, Ar), 7.29 (t, 2H, J ¼ 7.8 Hz, Ar),
7.49 (d, 2H, J ¼ 8.4 Hz, Ar), 7.67 (s, 1H, J ¼ 8.7 Hz, CH).
MS (APClþ, 20 V), m/z (%) ¼ 501 [M þ H]þ, 423, 332.
2.2.2. Tris(4-formylphenyl)amine tri(N-phenylhydrazone) (5)
Compound 5 was synthesized from phenylhydrazine (1 ml,
10.4 mmol) and trialdehyde 3 (0.5 g, 1.7 mmol) by the same
procedure as compound 4.
The yield of 5 was 0.9 g (88%).
IR (KBr),
1596, 1497, 1446 (ar. C]C), 1321 (CeN), 1259 (CeOeC).
1H NMR (CDCl3),
(ppm): 3.84 (s, 3H, NH), 6.69e6.72 (m, 6H, Ar),
n
/cmꢂ1: 3309 (NeH), 3028 (ar. CeH), 2959 (alif. CeH),
2.2. Materials
d
The starting compounds aniline (Aldrich), 4-iodanisole (Aldrich),
triphenylamine (Aldrich), phenylhydrazine (Fluka), 1-(chlor-
omethyl)-4-vinylbenzene (Aldrich), and the required chemicals, i.e.
copper powder (Aldrich), 18-crown-6 (Aldrich), phosphorous (V)
6.76 (t, 3H, J ¼ 8.2 Hz, Ar), 6.85e6.89 (m, 6H, Ar), 6.95e7.01 (m, 9H,
Ar, CH), 7.03e7.06 (m, 6H, Ar).
MS (APClþ, 20 V), m/z (%) ¼ 600 [M þ H]þ, 510, 313, 245.
R4
R4
R3
R3
N
R2
R2
R1
R1
H
N
N
H2N
Cl
N
N
POCl3/DMF
N
N
N
N
O
H
1, TPA
2, 3
4, 5
6, 7
R1
R2
R3
R4
OCH3
1
OCH3
2
OCH3
4
5
OCH3
6
H
CH N N
CH N N
TPA
H
3
CHO
7
Scheme 1. Synthetic routes compounds 6 and 7.

V. Mimaite et al. / Dyes and Pigments 95 (2012) 47e52
49
O
HA
CH2
N
N
HX
N
HM
JAM = 17,6 Hz
JAX = 10,9 Hz
JMX = 0,7 Hz
HM
HX
O
HA
6.60
6.60
6.40
6.40
6.20
6.20
6.00
6.00
5.80
5.80
5.60
5.60
5.40
5.40
5.20
5.20
ppm
Fig. 1. Fragment of 1H NMR spectrum of hydrazone monomer 6 in CDCl3.
2.2.3. 4-(Bis(4-metoxyphenyl)amino)benzaldehyde N-4-
vinylbenzyl-N-phenylhydrazone (6)
5.72 (dd, 1H AMX of system CH]CH2 proton HM trans JAM ¼ 17.6 Hz
ir gem JMX ¼ 0.7 Hz), 6.69 (dd, 1H AMX of system CH]CH2 proton
HA), 6.81 (d, 4H, J ¼ 9.1 Hz, Ar), 6.86e6.93 (m, 3H, Ar), 7.04 (d, 4H,
J ¼ 8.7 Hz, Ar), 7.18 (d, 2H, J ¼ 8.1 Hz, Ar), 7.27 (d, 2H, J ¼ 9.9 Hz, Ar),
7.31e7.38 (m, 5H, Ar, C-H), 7.43 (d, 2H, J ¼ 8.8 Hz, Ar).
Hydrazone (4) (1 g, 2.4 mmol) was dissolved in 5 ml of acetone
and 1-(chloromethyl)-4-vinylbenzene (0.7 ml, 4.8 mmol) was
added drop-wise. The reaction mixture was heated to the reflux
temperature and tetrabutylammonium hydrogensulfate (0.008 g,
0.024 mmol) as well as KOH (0.81 g, 19.5 mmol) were added to the
reaction mixture. The later was added in three portions with 5 min
interval. After 30 min inorganic components were filtered off and
the solvent was removed by distillation. The product was purified
by column chromatography at the reduced pressure. The mixture of
ethyl acetate and hexane in a volume ratio of 1:5 was used as an
eluent. The resin-like crude product was dissolved in diethyl ether
and precipitated into the methanol. It was recrystallized from
methanol.
MS (APClþ, 20 V), m/z (%) ¼ 540 [M þ H]þ, 539, 423, 332.
2.2.4. Tris(4-formylphenyl)amine tri(N-4-vinylbenzyl-N-
phenylhydrazone) (7)
Compound 7 was synthesized by the same procedure as
compound 6 using hydrazone 5 (0.8 g, 1.3 mmol),1-(chloromethyl)-
4-vinylbenzene (1.1 ml, 7.9 mmol), tetrabutylammonium hydro-
gensulfate (0.004 g, 0.013 mmol) and KOH (1.3 g, 23.4 mmol). The
target compound was purified by column chromatography at the
reduced pressure using ethyl acetate and hexane in a volume ratio
of 1:9 as an eluent.
The yield of 6 was 0.6 g (46%), mp. 64e66 ꢀC.
IR (KBr),
n
/cmꢂ1: 3039 (ar. CeH), 2970, 2933 (alif. CeH), 2836
The yield of 7 was 0.5 g (42%).
(OeCH3), 1585, 1516, 1484 (ar. C]C), 1387 (C¼NeN), 1338 (CeN),
IR (KBr),
C), 1394 (C]NeN), 1318 (CeN), 1628, 990, 908 (CH]CH2).
1H NMR (CDCl3),
(ppm): 5.15 (s, 6H, CH2), 5.23 (dd,1H of system
n
/cmꢂ1: 3036, 3005 (ar. CeH), 1596, 1508, 1496 (ar. C]
1258 (CeOeC), 1630, 992, 910 (CH]CH2).
1H NMR (CDCl3),
d
(ppm): 3.79 (s, 6H, OCH3), 5.13 (s, 2H, CH2),
d
5.22 (dd, 1H AMX of system CH]CH2 proton HX cis JAX ¼ 10.9 Hz),
AMX CH]CH2 proton HX cis JAX ¼ 10.9 Hz), 5.71 (dd, 1H of system
AMX CH]CH2 proton HM trans JAM ¼ 17.6 Hz ir gem JMX ¼ 0.7 Hz),
6.69 (dd, 1H of system AMX CH]CH2 proton HA), 6.93 (t, 3H,
J ¼ 7.2 Hz, Ar), 7.03 (d, 6H, J ¼ 8.8 Hz, Ar), 7.19 (d, 6H, J ¼ 8.1 Hz, Ar),
7.27e7.39 (m, 21H, CH, Ar), 7.49 (d, 6H, J ¼ 8.4 Hz, Ar).
1.2
MS (APClþ, 20 V), m/z (%) ¼ 949 [M þ H]þ, 948, 832, 740, 327.
6
7
1.0
3. Results and discussion
TPA
The synthetic routes to hydrazones with reactive vinyl groups
(6, 7) are shown in Scheme 1. The first step was Ullmann coupling
reaction to get triphenylamine derivative 1 with methoxy groups at
para position. The second step was formylation of compounds 1 and
triphenylamine (TPA) by the method of Vilsmeier. The next step
was the condensation of aldehydes 2, 3 with phenylhydrazine. In
0.8
0.6
0.4
0.2
0.0
Table 1
The optical characteristics of 6, 7 and TPA.
Compound
UV, lmax (nm)
PL, lmax (nm)
225
250
275
300
325
350
375
400
425
450
6
7
TPA
206, 248, 298, 378
206, 252, 303,401
206, 236, 299
448
448
Wavelength, nm
Fig. 2. UV spectra of dilute THF solutions of monomers 6, 7 and TPA.

50
V. Mimaite et al. / Dyes and Pigments 95 (2012) 47e52
Table 2
Thermal characteristics of 6 and 7.
52 oC
a
b
Compound
Tdeg-5% (ꢀC)
Tm (ꢀC)
Tg (ꢀC)
2
heating
6
7
307
315
65
e
52
82
a
First heating scan.
Second heating scan.
b
cooling
heating
1
the last step monomers 6 and 7 were obtained by interaction of
compounds 4, 5 with 1-(chloromethyl)-4-vinylbenzene. All the
reactions were controlled by TLC. The synthesized compounds
were purified by column chromatography and characterized by IR-,
1H NMR- and mass spectrometries.
65 C
70
The proton signals of methoxy groups at 3.79 ppm are present in
the 1H NMR spectrum of compound 6. The characteristic signals of
vinyl groups are observed in the 1H NMR spectra of the hydrazone
monomers (6, 7). Three protons of vinyl group form three-spin
AMX system (Fig. 1). According to the coupling constants protons
are assigned to the corresponding signals. The signals of HA protons,
which are near benzene ring, are observed at 6.69 ppm. The signals
of HX and HM protons are observed at 5.22e5.23 ppm and
5.71e5.72 ppm respectively. The signals of CH2 group protons of the
hydrazone moiety of compounds 6 and 7 are observed at 5.13 and
5.15 ppm respectively.
20
30
40
50
60
80
Temperature, oC
Fig. 4. DSC curves of 6 at the heating/cooling rate of 10 ꢀC/min in N2 atmosphere.
Compounds 6, 7 exhibit blue fluorescence when excited with UV
irradiation. Their fluorescence maxima appear at 448 nm.
The thermal properties of hydrazones 6, 7 were studied by DSC
and TGA. The temperatures of thermal transitions are summarized
in Table 2.
Compounds 6, 7 demonstrate relatively high thermal stability.
Their 5% weight loss temperatures are 307 ꢀCe315 ꢀC respectively.
These are rather high stabilities as for aromatic hydrazones. Earlier
reported 5% weight loss temperatures for carbazole-based hydra-
zones ranged from 260 ꢀC to 290 ꢀC [25]. Thermogravimetric curves
of compounds 6, 7 is shown in Fig. 3. The thermal degradation of
both hydrazones (6 and 7) occurs in two stages however the
mechanism of the process is clearly dependent on the number of
hydrazone moieties in the molecule. The rate of the thermal
decomposition of compound 7 containing three hydrazone moie-
ties is considerably slower than that of compound 6 having one
hydrazone moiety.
Absorption bands of NH group observed in the IR spectra of
hydrazones 4, 5 at 3309e3319 cmꢂ1 disappear in the spectra of
monomers 6, 7. The characteristic stretches of vinyl groups appear
in the IR spectra of hydrazones 6,
7 ,
at 1628e1630 cmꢂ1
990e992 cmꢂ1 and 910-908 cmꢂ1
.
Mass spectra of all the synthesized compounds show the cor-
responding molecular ion peaks.
UV spectra of dilute solutions of compounds 6, 7 and that of TPA
in THF are given in Fig. 2. The wavelengths of absorption maxima
are summarized in Table 1.
Absorption of hydrazones 6, 7 is red shifted with respect to that
of TPA. This shift can be attributed to
consequence of increased conjugated
p
p
/
p
* transitions and is the
-electron system due to the
incorporation of hydrazone moeities into the structure of TPA. The
lowest energy absorption band of compound 7 having three
hydrazone moieties is red shifted with respect of that of compound
6 containing one hydrazone moiety.
DSC investigations revealed that hydrazone monomer 6 could
exist both in crystalline and amorphous states while compound 7
100
6
7
80
60
40
20
0
100
200
300
400
500
600
Temperature, oC
Fig. 5. DSC curves of
atmosphere.
6 and 7
at the heating/cooling rate of 10 ꢀC/min in N2
Fig. 3. TGA curves of monomers 6, 7 at the heating rate of 20 ꢀC/min in N2 atmosphere.

V. Mimaite et al. / Dyes and Pigments 95 (2012) 47e52
51
4
3
2
1
0
-1
-2
-3
0
0.1
0.2
0.3
0.4
0.5
E vs Fc/Fc+ (V)
Fig. 7. Cyclic voltammogram of 6 at a scan rate of 50 mVsꢂ1
.
containing three reactive vinyl groups started at the lower
temperature. Only one exothermal polymerization signal with the
maximum at 167 ꢀC was observed for this monomer apparently due
to the higher propagation rate. Unfortunately we were not able to
fix the glass transition temperature of the product of polymeriza-
tion of 7, apparently due to insufficient sensibility of the apparatus
used.
The IR spectroscopy was used to examine the extent self-
polymerization. The characteristic stretches of vinyl groups of
monomers 6 and 7 are found at around 1630 cmꢂ1, 990 cmꢂ1 and
908 cmꢂ1 [28,29]. After self-polymerization initiated by heating,
stretch of vinyl group in the higher frequencies disappear (Fig. 6).
The stretches in the fingerprint region disappear or considerably
decrease.
Fig. 6. Fragments of IR spectra of hydrazone monomer 7 (a) and of the product of its
self-polymerization (b).
was found to be amorphous. The DSC thermogram of hydrazone 6 is
presented in Fig. 4. The first DSC heating scan of 6 showed endo-
thermic melting signal 65 ꢀC. No signal of crystallization was
observed in the cooling scan and the following heating scan
revealed only a glass transition at 52 ꢀC.
The electrochemical data of compounds 6, 7 are presented in
Table 3. The cyclic voltammogram of 6 is shown in Fig. 7. The same
values of anodic and cathodic peaks were observed for five times
repeated cycles. During the oxidative scan, an anodic peak was
observed which can be attributed to the formation of cation radical.
The reverse scan showed a reduction process indicating a good
electrochemically stability. The oxidation potentials were calcu-
lated as the average of the anodic and cathodic peak potentials. The
easier oxidation of 6 compared to 7 can be explained as due to the
presence of electron-rich methoxy groups. The HOMO energy levels
established from the oxidation potentials are comparable (ꢂ4.91 eV
and ꢂ4.97 eV). The LUMO energy levels were calculated from
HOMO and optical band gap values. Compound 7 showed lower
LUMO energy level (ꢂ2.11 eV) than compound 6 (ꢂ1.93 eV).
The photoelectrical characteristics of compounds 6, 7 are
summarized in Table 4. The ionization potentials (Ip) values of the
amorphous films of monomers 6 and 7 were found to be compa-
rable (5.22 and 5.29 eV).
Compound 7 exhibited only glass transition in the first and the
following DSC scans. Hydrazone 7 having three hydrazone moieties
showed by 30 ꢀC higher glass transition temperature than
compound 6 with one hydrazone substituent. This observation can
apparently be explained by the higher molecular weight of
compound 7 which results in stronger intermolecular interaction.
Self-polymerization of the monomers 6 and 7 was studied by
DSC. The results are presented in Fig. 5. During the heating scan of 6
two exothermic peaks were observed with maxima at 161 ꢀC and
209 ꢀC. It can be assumed that the first peak is due to the step of
thermal-initiation and the second one is due to the propagation
[26]. These results are comparable with the earlier reported
observation. Huang at al. [27] observed self-polymerization of
aromatic amine with two vinyl groups in the range of 150e180 ꢀC.
The glass transition temperature of the product of polymerization
of 6 was found to be 97 ꢀC which is considerably higher than that of
the monomer (6) itself (52 ꢀC). Self-polymerization of monomer 7
Charge-transporting properties of the layers of compounds 6, 7
prepared by spin coating were estimated by XTOF technique. The
electric field dependencies of hole-drift mobilities of the layers of 6,
Table 3
Electrochemical characteristics of 6 and 7.
Table 4
Photoelectrical characteristics of 6 and 7.
Compound
Eox (V)
HOMOa (eV)
Egoptb (eV)
LUMOc (eV)
a
Compound
Ip (eV)
m0 (cm2/Vs)
m
b (cm2/Vs)
6
7
0.11
0.17
ꢂ4.91
ꢂ4.97
2.98
2.86
ꢂ1.93
ꢂ2.11
6
7
5.22
5.29
2,8 ꢁ 10ꢂ5
2,2 ꢁ 10ꢂ3
9 ꢁ 10ꢂ5
3,5 ꢁ 10ꢂ3
a
HOMO ¼ 4.8 þ Eox
.
Obtained from UV spectra Egopt ¼ 1240/lonset
.
Zero field mobility.
b
c
a
LUMO ¼ HOMO e Egopt
.
At an electric field of 6.4 ꢁ 105 cm2/V.
b

52
V. Mimaite et al. / Dyes and Pigments 95 (2012) 47e52
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2008;18:4495e509.
7 are presented in Fig. 8. Compound 7 having three hydrazone
moieties exhibited better charge-transporting properties. Hole-
drift mobility in the layer of 7 reached 3.5 ꢁ 10ꢂ3 cm2/V at an
electric field of 6.4 ꢁ 105 cm2/V.
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4. Conclusions
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Two triphenylamine-based hydrazones with reactive vinyl
groups were synthesized and their properties were studied. The
synthesized monomers form glasses with glass transition temper-
atures ranging from 52 ꢀC to 82 ꢀC. Ionization potentials of hydra-
zone monomers are comparable and range from 5.22 eV to 5.29 eV
as determined by electron photoemission method. Time-of-flight
hole-drift mobility of hydrazone monomer having three hydra-
zone moieties with vinyl groups is 3.5 ꢁ 10ꢂ3 cm2/V at an electric
field of 6.4 ꢁ 105 cm2/V. The possibility of self-polymerization of the
synthesized monomers was demonstrated by differential scanning
calorimetry. Self- polymerization of compound having three
hydrazone moieties starts at lower temperature than of hydrazone
with one reactive functional group.
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Acknowledgments
Financial support of this research by the Research Council of
Lithuania (project No. MIP-64/2010) is gratefully acknowledged. Dr.
habil. Valentas Gaidelis is thanked for the help in the measure-
ments of ionization potentials.
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