Synthesis and luminescent properties of new blue polymer light-emitting diodes material, poly(9-(3-vinyl-phenyl)-pyrene)

Article abstract of DOI:10.1166/jnn.2017.14119

Polymer light-emitting diodes (PLEDs) have attracted much attention from academia and industry field because PLED has advantage property that is well-suited to flexible lighting and solution processed device. In this paper, we suggest new blue emitting polymer based on pyrene, poly(9-(3-Vinyl-phenyl)-pyrene) (PVPPy). From NMR data, vinyl group protons were disappeared and aromatic protons showed broad proton peaks because of polymer characteristics. PVPPy film can be obtained from spin coating with solution used by common solvents. It exhibited photoluminescence (PL) maximum value of 468 nm and full width at half maximum (FWHM) value of 73 nm. Three dopants for green, red, yellow were used to PVPPy, all energy transfer was happened well.

Full text of DOI:10.1166/jnn.2017.14119

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Vol. 17, 5669–5672, 2017
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Synthesis and Luminescent Properties of New Blue
Polymer Light-Emitting Diodes Material,
Poly(9-(3-Vinyl-phenyl)-pyrene)
Minjin Jo2, Garam Yang2, Hayoon Lee1, Jaehyun Lee3, Hyocheol Jung1, and Jongwook Park1ꢀ∗
1Department of Chemical Engineering, Kyung Hee University, Gyeonggi-do, 17104, Republic of Korea
2Department of Chemistry, Catholic University of Korea, Bucheon, 420-743, Korea
3Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan
Polymer light-emitting diodes (PLEDs) have attracted much attention from academia and indus-
try field because PLED has advantage property that is well-suited to flexible lighting and solution
processed device. In this paper, we suggest new blue emitting polymer based on pyrene, poly(9-
(3-Vinyl-phenyl)-pyrene) (PVPPy). From NMR data, vinyl group protons were disappeared and aro-
matic protons showed broad proton peaks because of polymer characteristics. PVPPy film can be
obtained from spin coating with solution used by common solvents. It exhibited photoluminescence
(PL) maximum value of 468 nm and full width at half maximum (FWHM) value of 73 nm. Three
dopants for green, red, yellow were used to PVPPy, all energy transfer was happened well.
IP: 46.161.63.84 On: Thu, 29 Mar 2018 11:32:36
Keywords: Polymer Light-Emitting Diodes (PLEDs), Blue Emitting Polymer, Pyrene.
Copyright: American Scientific Publishers
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1. INTRODUCTION
in this field is to develop new conjugated polymers with
high luminescent performance.
Polymer light-emitting diodes (PLEDs) can be applied to
various areas such as flat-panel displays and lighting, and
thus is drawing much attention from academia and indus-
try areas.1–4 Especially, the interest in PLED using con-
jugated polymers5ꢀ6 has augmented because PLED have
properties that are well-suited to flexible lightings: good
processibility,7 low operating voltages, and facile color
tunability over the full visible range.
Pyrene and its derivatives as blue fluorescent emitter
have been recently received the spotlight because they
have high quantum efficiency as well as the thermal and
chemical stabilies.12 We synthesized and intend to intro-
duce poly(9-(3-vinyl-phenyl)-pyrene) (PVPPy), which is a
new blue emitting polymer based on pyrene as the blue
host material.
Within recent several years, many light-emitting poly-
mers have been developed, and the efficiency is increasing.
As blue OLED, poly(para-phenylene)(PPP)8 was
first used, and various conjugated polymers including
polyfluorenes(PFs)9, poly(p-phenylenevinylene)(PPVs),10
poly(phenanthrene)11 and such are being used as the blue
emitter.
Nevertheless, although the performance of PLED is
being improved, the parts that still need to be resolved,
such as electroluminescent (EL) efficiencies or lumines-
cent stability, are currently hindering commercialization.
Therefore, one of the things that need to be resolved first
2. EXPERIMENTAL DETAILS
2.1. General Experiment
The reagents and solvents used in the synthesis were pur-
chased as reagent grade and used without further refine-
ment. All the reactions were executed with the use of
dry glassware in nitrogen condition. As for the TLC
used in the analysis, Merck 60 F254 silica gel plate was
used, and in column chromatography, Merck 60 silica gel
(230–400 mesh) was used.
2.2. Synthesis of Compound 1
1-Bromo-pyrene 10 g was added to 500 mL round floor
flask, melted in anhydrous tetrahydrofuran (THF) 120 mL,
∗Author to whom correspondence should be addressed.
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doi:10.1166/jnn.2017.14119
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Synthesis and Luminescent Properties of New Blue PLEDs Material, PVPPy
Jo et al.
and agitated. After reaction temperature was set to −78 ꢀC,
2.0 M n-Butyllithium 23.4 mL (50.59 mmol) was added
into reaction mixture slowly. In 10 minutes, triisopropyl
borate 10 mL was added to reaction mixture. When reac-
tion temperature increased to room temperature in an hour,
12 M HCl 7.2 mL was added. The reaction was com-
pleted, compound was extracted with ethyl acetate (EA)
and water, and the organic layer was dried with anhydrous
MgSO4 and filtered. After the compound was concentrated
under reduced pressure, white solid was obtained in 51%.
1H-NMR (300 MHz, THF-d8) ꢁ (ppm): 8.89–8.85
(m, 1H), 8.32–8.28 (m, 1H), 8.21–8.15 (m, 3H), 8.14–8.03
(m, 3H), 8.01–7.94 (m, 1H), 7.10 (s, 2H).
the reaction mixture was melted in small amount of chlo-
roform. The reaction mixture was recrystallized to excess
amount of methanol, and white solid polymer was obtained
in 55%.
1H-NMR (300 MHz, CDCl3) ꢁ (ppm): 8.01–6.24 (broad
peaks, aromatic rings), 1.65–1.21 (alkyl groups).
2.6. Characterization
As for 1H-NMR spectrum Bruker, AM-300 spectrome-
ter was used, and as for chemical shift values, ppm unit
was recorded. UV-Visible (UV-Vis) spectra were measured
with HP 8453 UV-VIS-NIR spectrometer, and PL spectra
were measured with the use of Perkin Elmer luminescence
spectrometer LS50 (Xenon flash tube). Polymer molecular
weight and polydispersity were measured through gel per-
meation chromatography (GPC) analysis with the use of
chloroform solvent.
2.3. Synthesis of Compound 2
Compound (1) 6 g, Pd(PPh3ꢂ4 0.564 g, 3-bromobenzalde-
hyde 0.118 ml was added to 500 ml round bottom flask,
and melted with toluene 100 ml/ethanol 33 ml. The mix-
ture was stirred under nitrogen at 70 ꢀC, 2 M K2CO3
1.52 ml was added to reaction mixture. After the reaction
was completed, the compound was extracted with toluene
and water, and then the organic layer was dried with
anhydrous MgSO4 and filtered. The reaction mixture was
purified to 1st column with toluene solvent. The reaction
mixture was purified again to 2nd column at THF:hexane =
1:12 ratio. After the solvents were removed in room tem-
perature, white solid substance was obtained in 35%.
2.7. Luminescent Properties
Polymer film was produced through spin coating with the
use of polymer solution that includes 1 wt% of toluene
solvent.
3. RESULTS AND DISCUSSION
Main motivation of this PVPPy is based on suggestion of
general blue emitting material. Other typical blue poly-
mers such as PPV or fluorene have synthetic scheme of
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1H-NMR (300 MHz, THF-d8) ꢁ (ppm): 10.88–10.13
(m, 1H), 8.32–8.20 (m, 3H), 8.18–8.18 (m, 3H), 8.11–8.00
(m, 2H), 7.96–7.91 (m, 3H), 7.80–7.74 (m, 2H).
Copyright: American Scientific Publishers
more than 7 steps. On the other hand, monomer could
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be obtained through simple 3 steps as in Scheme 1, and
through high-polymerization, the high polymer which can
be used as host material was obtained. For usages of facile
blue polymer preparation, such synthetic scheme is a great
advantage.
Especially, for a large band gap, PVPPy was molecule-
designed to have meta-linkage between phenyl group and
pyrene group. Meta position has the advantage that it has
shorter conjugation length and relatively wider band gap
compared to ortho and para position.13 Examining NMR
data, due to the characteristics of high polymer, protons of
vinyl group disappear and aromatic proton exhibit broader
proton peaks.
Figures 1 and 2 respectively show UV-Visible (UV)
absorption and photoluminescence (PL) spectra for PVPPy
and monomer in solution state and film state. This data
was briefly organized in Table I. In solution, monomer
exhibits maximum absorption wavelength of 281, 346 nm
and polymer exhibits similar values at 282, 347 nm, and
also in film state, monomer exhibits maximum absorption
wavelength of 286 nm, 355 nm, and polymer exhibits sim-
ilar values at 288 nm, 363 nm.
2.4. Synthesis of Monomer
Methyltriphenylphosphonium bromide 6.65 g (18.61 mmol)
and KOC(CH3ꢂ3 2.24 g (19.85 mmol) were added to
500 ml round bottom flask, melted with 150 ml anhy-
drous THF, and agitated for an hour while remaining at
ꢀ
0 C. The reaction mixture was extracted with methylene
chloride (MC) and water, and then the organic layer was
dried with anhydrous MgSO4 and filtered. The reaction
mixture was purified to column with mixed solvent of
Chloroform:hexane (1:10). After the product was concen-
trated under reduced pressure, white solid substance was
obtained in 45%.
1H-NMR (300 MHz, THF-d8) ꢁ (ppm): 8.23–8.18
(m, 1H), 8.17–8.12 (m, 5H), 8.10–7.97 (m, 3H), 7.71–7.69
(m, 1H), 7.59–7.49 (m, 3H), 6.91–6.81 (m, 1H), 5.92–5.85
(dd, 1H), 5.31–5.26 (dd, 1H).
2.5. Synthesis of Poly(9-(3-Vinyl-phenyl)-pyrene)
(PVPPy)
Monomer 0.2 g (0.66 mmol) and azobisisobutynitrile
0.02 g (0.12 mmol) were added to 100 ml round bot-
tom flask in nitrogen, and melted with 4 ml anhydrous
benzene solvent. The polymer was agitated for 12 hours
In case of PL, monomer and polymer have PL maximum
values of 396 nm, 476 nm respectively in solution state,
and of 475 nm, 468 nm respectively in film state. In case
of monomer PLmax in film state, it could be understood
by relatively the packed state of monomer film. However,
ꢀ
while remaining at 50 C. The reaction was completed,
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Jo et al.
Synthesis and Luminescent Properties of New Blue PLEDs Material, PVPPy
Scheme 1. Synthetic routes of PVPPy.
polymer in film state showed relatively unpacked state,
red and yellow dopants, were shown. As the result, dopant
emission was observed in each doped film, according to
which it could be verified that when the three dopants are
used with PVPPy host polymer, the energy transfer from
IP: 46.161.63.84 On: Thu, 29 Mar 2018 11:32:36
which cause 468 nm. In case of polymer solution state
(PLmax: 476 nm), it can be explained by the interaction
Copyright: American Scientific Publishers
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between polymer and solvent.
In Figure 3, PL emission of PVPPy and solution UV
spectra respectively of C545T, DCM, and rubrene, which
are green, red, and yellow dopants, were shown. UV spec-
tra of the three dopants overlaps with PVPPy emission.
Through this data, it can be predicted that when each of
the three dopants are used with PVPPy host, the energy
transfer from host to dopant occurs smoothly.
In Figure 4, PL spectra of PVPPy spin-coated film
doped with C545T, DCM, and rubrene, which are green,
Figure 2. UV-visible absorption and PL spectra of monomer (square)
and PVPPy (triangle) in spin coated film.
Table I. Optical properties of monomer and PVPPy.
Solutiona
Filmb
Compounds UVmax (nm) PLmax (nm) UVmax (nm) PLmax (nm)
Monomer
Polymer
(PVPPy)
281, 346
282, 347
396
476
286, 355
288, 363
475
468
Figure 1. UV-visible absorption and PL spectra of monomer (square)
and PVPPy (triangle) in Chloroform solution (1ꢃ0×10−5 M).
Note: aChloroform solution (1×10−5 M), bSpin coating film(1 wt%).
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Synthesis and Luminescent Properties of New Blue PLEDs Material, PVPPy
Jo et al.
4. CONCLUSION
Through simple 4 steps, the new blue emitter of PVPPy
was synthesized. In spin-coated film, it yields the emission
of 468 nm. When PVPPy is applied as the host material
to the three dopants of C545T, DCM, and rubrene, energy
transfer occurs smoothly, and thus it is suitable as the host
material. Also, it has a large FWHM of 73 nm, and thus is
expected to be applied to white OLED, and is also a good
candidate for OLED lighting device with high CRI value.
Acknowledgment: This research was supported by a
grant from the Technology Development Program for
Strategic Core Materials funded by the Ministry of
Trade, Industry and Energy, Republic of Korea (Project
No. 10047758).
Figure 3. UV spectra of (•) C545T, (ꢀ) rubrene, (ꢁ) DCM in toluene
solution and the PL emission of (ꢂ) PVPPy film as host.
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Figure 4. PL spectra of PVPPy film and PVPPy films doped with var-
ious dopants. ((ꢂ) PVPPy, (•) PVPP+ C545T 8%, (ꢀ) PVPP+ rubrene
8%, (ꢁ) PVPP+DCM 8%).
blue color to each color occurs smoothly. We believe that
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used with an appropriate yellow dopant, it is expected that
white OLED device of solution process could be produced.
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Received: 2 June 2016. Accepted: 7 September 2016.
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