Synthesis of Luminescent Polystyrene with φ-Conjugated Pendant

Article abstract of DOI:10.14233/ajchem.2013.oh66

One novel polystyrene-based copolymer (PS-PF) with φ-conjugated unit (fluorneyl and phenyl rings) as pendant was designed and synthesized using radical polymerization method and initiated by AIBN (2,2'- azobisisobutyronitrile) from the new functional mono

Full text of DOI:10.14233/ajchem.2013.oh66

Asian Journal of Chemistry; Vol. 25, No. 10 (2013), 5700-5702
http://dx.doi.org/10.14233/ajchem.2013.OH66
Synthesis of Luminescent Polystyrene with π-Conjugated Pendant†
*
FENG WANG and CAI-XIA ZHU
School of Materials Science and Chemical Engineering, Anhui University of Architecture, Hefei 230022, P.R. China
*Corresponding author: E-mail: wangfeng@aiai.edu.cn
AJC-13309
One novel polystyrene-based copolymer (PS-PF) with π-conjugated unit (fluorneyl and phenyl rings) as pendant was designed and
synthesized using radical polymerization method and initiated by AIBN (2,2'-azobisisobutyronitrile) from the new functional monomer,
which contained the conjugated unit and reactive double bond. Nuclear magnetic resonance, FT-IR and UV-visible spectra were used to
characterize the structure of intermediate and copolymer. The PS-PF is easily dissolved in organic solvent such as THF and CH3Cl and to
be formed thin film by spin coating. The ink-jet printing method was applied to form blue pattern. The strongest emission of the as
prepared copolymer was at 416 nm with shoulder peak of 441 nm in the solution and 440 nm with shoulder peak in the film state.
Key Words: Polystyrene, Conjugated unit, Pendant, Photoluminescent.
copolymer of polystyrene and conjugated polymers can free
from rigid conditions needed in ATRP or RAFT routes.
INTRODUCTION
π-Conjugated polymers or oligomers have been subject
of growing interest in the past decades because they have been
found wide applications in polymeric light-emitting diodes,
solar cells, transistors chem.-sensors, etc.1-4. Remarkable
progresses have been achieved in the development of these
kinds of conjugated polymers and oligomers, particularly those
π-conjugated polymer with special molecules structure, such
as block copolymer containing the rod-coil segment in
the main-chain, dendrimer and hyper-branched conjugated
polymer5-7. There is little report to synthesize polymer
containingp-conjugated unit as pendant.
EXPERIMENTAL
The reactive monomer V (Scheme-I) containing double
bond was first synthesized. The monomer V was synthesized
from 2,7-dibromo-fluorene (I). The middle-product of 2,7-
dibromo-9,9-di-n-dodecylfluorene (II) and the 3,7-bromo-9,9-
di-n-dodecylfluoren-2-ylboronic acid (III) in Scheme-I were
prepared by the previous literature8.
The title copolymer of PS-PF was synthesized according
to the reaction sequence outlined in the Scheme-I. Styrene
(St) was purified by treating with 5 wt % aqueous NaOH to
remove the inhibitor. AIBN is re-crystallized from THF
before usage. Monomer V and styrene (1:1 molar ratio) were
dissolved in 20 mL anhydrous DMF and flowed with pure
nitrogen to remove O2 for 30 min. The reaction system were
heated to 800 ºC for 36 h. The viscosity of the reaction system
increased obviously. The fresh copolymer was dissolved in
THF and deposited by adding methanol, then filtered and
vacuum dried. The product PS-PF was powder-like.
Nuclear magnetic resonance (1H NMR) spectra were
collected on Bruker Avance 300, with chloroformd as a
solvent and tetramethylsilane (TMS) as an internal standard.
Fourier transform infrared (FT-IR) spectrum was recorded on
Shimadzu IR prestige-21 spectrometer. Ultraviolet-visible
(UV-VIS) absorption and fluorescence property were measured
Polystyrene (PS) is often regarded as general polymeric
materials. Many efforts have been done to introduce special
functional to polystyrene by co-polymerization route7-9.
Reactive Fe-phthalocyanine was used to react with styrene
monomer to produce magnetic micro spheres7. Chochos et al.8
synthesized the dumbbell-like C70 polystyrene derivatives.
Copolymer of polystyrene containing liquid crystalline unit
was obtained by Tsolakis et al.9. Thermo-sensitive functional
polymer based on polystyrene was prepared by using
macromonomer poly (N-vinylformamide)10.
In this paper, it is designed and prepared one reactive
monomer with double bond and classic radical polymerization
method can be used to conjugated polymer, which can provide
a new method to introduce photo-luminescent property to
general polymers like polystyrene. This route to synthesize
†Presented to the 6th China-Korea International Conference on Multi-functional Materials and Application, 22-24 November 2012, Daejeon, Korea

Vol. 25, No. 10 (2013)
Synthesis of Luminescent Polystyrene with π-Conjugated Pendant 5701
by using a Shimadzu UV-3150 UV-VIS-NIR spectrophoto-
meter and RF-5300PC luminescence spectrometer with a
xenon lamp as light source, respectively. The gel permeation
chromatography analysis was conducted on Shimadzu
10A in the eluent tetrahydrofuran with polystyrene as the
standard.
FT-IR spectrum is applied to confirm the structure of the
copolymer described in Scheme-I and is shown in Fig. 2. The
absorption of double bond (C=C) in 1640-1630 cm–1 could
not be seen in the spectrum. The molecular weight measure-
ment is performed by gel permeation chromatography in the
eluent THF using the calibration curve of polystyrene stan-
dards. From the gel permeation chromatography curve, it could
be seen that the number average-molecular weight (Mn) and
the weight-average molecular weight (Mw) of the resulted
PS-PF are 15,600 and 23,700 Daltons, respectively. Single peak
appeared in the gel permeation chromatography curve (Fig.
3), suggesting that product is copolymer, rather than the
1.
n
BuLi, THF -78oC, 1h
C6H13Br, 50%NaOH
DMSO 70oC, 12h
Br
Br
Br
Br
2. B(O
i
Pr)3, -78oC to RT
C6H13 C6H13
3. HCl
II
I
OH
1. Pd(PPh3)4 , DMF, K2CO3 120oC, 24h
Br
B
H
HOH2C
OH
2.
90oC, 6h
C6H13
C6H13
HOH2C
CH3
B(OH)2
physical mixed system.
C6H13 C6H13
III
IV
C
H
CH2
CH3
O
C
H2C
H2
C
H
C
0.45
CH2
C
C
CCl
C
O
H2C
AIBN
CH3
C
O
O
0.40
750.30797
CH2
815.88758
1618.27348
0.35
C6H13
C6H13
C6H13
C6H13
1460.11088
0.30
1149.5721
H
V
0.25
0.20
Scheme-I:Synthetic route to polystyrene copolymer with conjugated unit
as pendant
1732.07341
RESULTS AND DISCUSSION
600
900
1200
1500
1800
2100
2400
In this paper, monomer V is prepared by monomer IV
(containing OH group) and methacryloyl chloride, rather than
methacrylic acid, is because of its stronger reactive activity.
Wavenumber (cm-1)
Wavenumber (1/cm)
Fig. 2. FT-IR spectra of PS-PF
1
Fig. 1 is the H NMR spectrum of the monomer V and the
copolymer of PS-PF. The values of δ (ppm) at 7.29-7.91 are
indexed to H atoms in phenyl and fluorenyl ring. The δ = 6.23
and 5.66 in the NMR spectra of the monomer V indexing to H
atoms of reactive double bond is disappeared at the spectra of
the copolymer PS-PF, which implied that the monomer V and
styrene had been polymerization initiated by AIBN.
MM=n1=561005600
Mw = 23700
Mw= 23700
n
Mw/Mn = 1.52
Mw/Mn=1.52
Monomer V
0
50000
Fig. 3. Gel permeation chromatography analysis of the PS-PF
100000
150000
200000
0
1
2
3
4
5
6
7
8
Fig. 4 is the UV-visible absorption spectra of PS-PF in
the THF dilute solution. Its strongest absorption is at 377 nm
(4.29 ev) is related to π-π transition of π-conjugated fluorenyl
and phenyl pendant and observed in many other reported
π-conjugated polymers and oligomers. The film of PS-PF on
glass is produced using the spin coating from THF solution of
PS-PF. The photoluminescent properties of the thin film are
determined on the RF-5300PC (Shimazhu), which is shown
Copolymer of PS-PF
0
1
2
3
4
5
6
7
8
Fig. 1. 1H NMR spectra of monomer V and PS-PF

5702 Wang et al.
Asian J. Chem.
in Fig. 5. It could be seen that two emission peaks of as-
obtained PS-PF are at 443 nm and 418 nm. The two emission
peaks of PS-PF in THF dilute solution are close to its thin film
state. The difference of photo-luminescent properties between
two states is that 443 nm is strongest in the state of thin film,
while 418 nm in the THF solution. The longer emission in of
π-conjugated polymer is related to "excimers" formation
resulted of the interaction between conjugated units. This kind
interaction is stronger in the film state than in THF solution.
In general, the property of photo-luminescent is introduced to
polystyrene, one kind of general polymer. If co-polymeri-
zation monomer is methyl methacrylate or methyl acrylate,
rather than styrene, the property of photo-luminescent could
introduce their polymers.
The ink-jet printing is used to produce the pattern in white
paper shown in Fig. 6. The pattern displayed strong blue colour
when is irradiated by the laser of 330 nm wavelengths.
150
100
50
Fig. 6. Pattern on white paper by ink-jet printing
Conclusion
In conclusion, it has been succeeded in synthesizing
luminescent polystyrene with π-conjugated pendant. It
provided one new and simple method to combine general
polymers (PS, PMMA etc.) such as elasticity and mechanical
property, with optical activity fluorescence. This polystyrene
can be used as smart polymeric material and when it is stimu-
lated by light (short wavelength), it emission quickly within
nano-seconds.
0
ACKNOWLEDGEMENTS
The project is supported by Science and Technological
Fund of Anhui Province for Outstanding Youth (06044097)
and Nature Research Program ofAnhui Education Department
(KJ2009A148 and KJ2012Z052).
300
350
400
450
500
550
600
Wavelength (nm)
Wavelength (nm)
Fig. 4. UV-VIS spectrum of the THF solution of PS-PF
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418
in the THF solution
200
150
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300
400
500
600
700
Wavelength (nm)
Wavelenght (nm)
Fig. 5. Photoluminescent spectra of the PS-PF