Yellow emitting materials: Truxene-based conjugated hyperbranched polymer containing difluoroboron-diketonate complexes

Article abstract of DOI:10.1016/j.dyepig.2016.10.037

A series of novel hyperbranched polymers BF₂-HP(1–4) containing difluoroboron-diketonate complexes and truxene units have been synthesized. To achieve the target polymers, the precursors Boc-HP(1–4) were obtained through the Pd (0)-catalyzed Suzuki polymerization with an “A₂ + B₃” or “A₂ + B₂ + B₃” approach in different molar ratios. After the deprotection of Boc-groups, the reaction with BF₃ gave the polymers BF₂-HP(1–4). The new BF₂ containing polymers exhibited red-shifts in their UV–vis absorption and emission compared with their uncomplexed counterparts. The tunable hyperbranched architectures of BF₂-HP(1–4) resulted in diverse optical properties. With the decrease of linear units in BF₂-HP(1–4), the emission peaks in chloroform solution presented a significant blue-shift, whereas a red-shift was noted in films. Notably, the hyperbranched architectures could suppress the aggregation more effectively than the linear architectures not only in poor solvents such as DMF but also in the film states. In addition, these polymers showed high thermal stability, and good solubility in common organic solvents.

Full text of DOI:10.1016/j.dyepig.2016.10.037

Accepted Manuscript
Yellow emitting materials: Truxene-based conjugated hyperbranched polymer
containing difluoroboron-diketonate complexes
Xin Wen, Dongxin Zhang, Tianci Ren, Jinchong Xiao, Yonggang Wu, Libin Bai, Xinwu
Ba
PII:
S0143-7208(16)31051-8
10.1016/j.dyepig.2016.10.037
DYPI 5553
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 29 July 2016
Revised Date: 24 October 2016
Accepted Date: 25 October 2016
Please cite this article as: Wen X, Zhang D, Ren T, Xiao J, Wu Y, Bai L, Ba X, Yellow emitting materials:
Truxene-based conjugated hyperbranched polymer containing difluoroboron-diketonate complexes,
Dyes and Pigments (2016), doi: 10.1016/j.dyepig.2016.10.037.
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ACCEPTED MANUSCRIPT
Table of Contents
-
1 -

ACCEPTED MANUSCRIPT
Yellow Emitting Materials: Truxene-Based Conjugated Hyperbranched
a
Polymer Containing Difluoroboron-Diketonate Complexes
Xin Wen, Dongxin Zhang, Tianci Ren, Jinchong Xiao, Yonggang Wu, Libin Bai*, Xinwu Ba*
College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China
Abstract
A series of novel hyperbranched polymers BF -HP(1-4) containing difluoroboron-diketonate
2
complexes and truxene units have been synthesized. To achieve the target polymers, the precursors
Boc-HP(1-4) were obtained through the Pd(0)-catalyzed Suzuki polymerization with an “A + B ” or
2
3
“
A + B + B ” approach in different molar ratios. After the deprotection of Boc-groups, the reaction
2 2 3
with BF gave the polymers BF -HP(1-4). The new BF containing polymers exhibited red-shifts in
3
2
2
their UV-vis absorption and emission compared with their uncomplexed counterparts. The tunable
hyperbranched architectures of BF -HP(1-4) resulted in diverse optical properties. With the decrease
2
of linear units in BF -HP(1-4), the emission peaks in chloroform solution presented a significant
2
blue-shift, whereas a red-shift was noted in films. Notably, the hyperbranched architectures could
suppress the aggregation more effectively than the linear architectures not only in poor solvents such
as DMF but also in the film states. In addition, these polymers showed high thermal stability, and
good solubility in common organic solvents.
Keywords: Hyperbranched polymers; Difluoroboron-diketonate complexes; Optoelectronic
property; Truxene units; Suzuki polycondensation.
*
Corresponding author. Tel./fax: +86-312-5079317.
E-mail address: zhonggou556@hbu.edu.cn (L. Bai); baxw@hbu.edu.cn (X. Ba).
Postal address: No.180 Wusi East Road, Baoding City, 071002, Hebei, P.R.China
1

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1. Introduction
Organoboron π-conjugated polymers have attracted much interest in the last few decades because
of their unique electronic and optical properties [1-7]. Difluoroboron (BF ) β-diketonate
2
π-conjugated systems are fascinating subunits for fabricating emissive and electronic polymers, due
to their large molar absorption coefficient, high luminescence quantum yield and room-temperature
phosphorescence [8,9]. Several efforts have been devoted to the design and synthesis of polymers
containing difluoroboron β-diketonate units [10-14]. For instance, Fraser et al. found that
polycaprolactones containing difluoroboron β-diketonate units exhibited intense blue fluorescence
upon UV excitation and blue-shifted emission [15]. More recently, Chujo et al. have reported the
optical properties of conjugated polymers which can be effectively tuned by the ratios of
difluoroboron β-diketonate units in the main chain of polymers [16]. However, for π-conjugated
polymers, their optical properties strongly depended on the molecular structure and inter- or
intra-molecular interactions [17-20]. In particular, concentration-quenching often occurred because
of the non-specific aggregation of π-conjugated polymers. Therefore, the suppression of intra- and
inter- molecular π-π stacking in the solid state seemed to be important to overcome this problem.
Hyperbranched polymers have been widely used in many fields due to their three-dimensional
dentritic architectures, a high number of the terminal groups, as well as little chain entanglement
[
21-25]. Using the unique feature of hyperbranched polymers, the aggregation of π-conjugated
polymers may be effectively suppressed, which is beneficial for a higher light emitting efficiency.
On the base of this view, various kinds of π-conjugated hyperbranched polymers were synthesized
and used as active layers in optical materials such as polymer-based organic light emitting diodes
(OLEDs), field effect transistors, solar cells and biosensors [26-30]. The concept in our work is to
construct novel difluoroboron β-diketonate-containing hyperbranched conjugated polymers with
diverse optoelectronic properties, which might improve the performance of organic materials in the
application for OLED devices.
2

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In continuation of our previous work [31,32], we synthesized BF -complexed hyperbranched
2
polymers BF -HP(1-4) with different molar ratios of BF -diketonate complexes and truxene units
2
2
(
Scheme 1). The tunable hyperbranched architectures of BF -HP(1-4) resulted in diverse optical
2
properties. As expected, the results showed that the hyperbranched architecture effectively suppress
the aggregation and hyperbranched polymers BF -HP(1-4) emitted strong yellow light not only in
2
organic solvents, but also in poor solvent or in film. Additionally, thermal gravimetric analysis (TGA)
displays that they all exhibit good thermal stability.
2.
Results and Discussion
The synthetic routes to the monomers and polymers are outlined in Scheme 2. M1 was obtained
by the condensation reaction of the commercially available 4-bromoacetophenone and methyl
4
-bromobenzoate in the presence of NaH. Introduction of di-tert-butyl dicarbonate into M1 by
using 4-N,N-dimethylaminopyridine (DMAP) as the catalyst can produce M2. Monomers M3 and
M4 were synthesized in our lab according to a published procedure [33,34].
The hyperbranched polymers Boc-HP1-4 were prepared through Suzuki cross-coupling reaction
by using M2 as A , M3 as B and M4 as B , respectively, and 1-bromobenzene was employed to
2
2
3
cap the boron containing end groups (Scheme 2). In the synthesis process, the feed ratio between
boronic acid pinacol ester (-B) and -Br was always 1.65 (Table S1). In order to increase the linear
length in hyperbranched polymers, the amount of M2 kept constant while feed ratios between M3
and M4 increased (Table S1), affording hyperbranched polymers from Boc-HP1 to Boc-HP4,
correspondingly. In the absent of truxene monomer M4, linear polymer Boc-LP5 was obtained.
The yields of those polymers were 44%, 63%, 62%, 62% and 53%, respectively. The relative
lower yields of Boc-HP1 and Boc-LP5 might be ascribed to the gelation formation and the
incomplete reaction of M4, respectively.
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The number-average molecular weights (M ) of polymers were determined by gel permeation
n
chromatography (GPC) using THF as the eluent and a polystyrene standard (Fig. 1) and the results
were listed in Table 1. As shown in Fig. 1a, the M of Boc-HP1-4 and Boc-LP5 decreased with the
n
increase of linear length from Boc-HP1 to Boc-LP5. When M1 was used instead of M2, the M of
n
3
-1
polymers were much lower, less than 4 × 10 g mol , which might be ascribed to the interconversion
between the keto and enol [35]. OH-HP1-4 and OH-LP5 were obtained in high yields by removing
the O-Boc groups with piperidine in methylene chloride (Scheme 2). Complex of OH-HP1-4 and
OH-LP5 with BF ·Et O gave polymers BF -HP1-4 and BF -LP5 [16], respectively, and the total
3
2
2
2
yields were in the range of 41% to 59%. After boron complexation, the M decreased (Fig. 1b).
n
Furthermore, the M and molecular weight distributions (M /M ) of BF -HP1-4 and BF -LP5 were
n
w
n
2
2
4
-1
2
.17-1.21×10 g mol and 8.01-1.69, respectively (Table 1). (Table 1). It should be noted that these
polymers BF -HP1-4 and BF -LP5 displayed better solubility in common organic solvents such as
2
2
tetrahydrofuran, methylene chloride, chloroform than that of linear counterparts [16], which might
result from the hyperbranched architectures.
The optical properties of the hyperbranched polymers were investigated by UV-Vis absorption
(Fig. 2a, c, e) and photoluminescence (PL) spectra (Fig. 2b, d, f) in dilute chloroform solution.
Boc-HP1 presented the absorption peaks at 318 nm and 371 nm (Fig. 2a). Upon the increase of
fluorene units in the polymers, Boc-HP2-4 and Boc-LP5 displayed the broad absorption bands at
376 nm, 378 nm, 378 nm, 383 nm, while the peak at 318 nm decreased gradually. In comparison, the
absorption spectra of OH-HP1-4 and OH-LP5 displayed a negligible change relative to their O-Boc
protected counterparts (Boc-HP 1-4) (Fig. 2c). After complexed with BF , however, the
3
BF -complex polymers BF -HP1-4 and BF -LP5 showed an obvious red-shift to 460 nm, and the
2
2
2
absorption peaks became broad (Fig. 2e). It might be ascribed to the formation strong push (truxene
parts)-pull (BF -complex moiety) systems that could lead to intramolecular charge transfer (ICT)
2
state [36,37].
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Fig. 2b showed the emission spectra of Boc-HP1 with the maximum peak at 467 nm. In the case of
Boc-HP2-4 and Boc-LP5, the emission peaks blue-shifted to 465 nm, to 464 nm, to 461 nm and 457
nm. OH-HP1-4 and OH-LP5 also displayed the same trend, but they emitted strong blue light (Fig.
2
d). This might be attributed to the removal of electron-withdrawing units (Boc). The BF -complex
2
polymers BF -HP1-4 and BF -LP5 exhibited significant red-shift spectra as shown in Fig. 2f, and
2
2
these polymers emitted strong yellow light. Clearly, with the increase of linear length in
hyperbranched architectures, polymers featured blue-shift emission profile from BF -HP1 to
2
BF -LP5, which was consistent with the absorption results. It is apparent that the delocalization
2
effect of fluorine units was smaller than that in truxene units, thus the band gap of conjugate system
became larger, resulting in a blue-shift from BF -HP1 to BF -LP5. Furthermore, the quantum yields
2
2
of BF -HP1-4 and BF -LP5 were measured using N,N′-bis(1-ethylpropyl)-3,4,9,10-perylene-bis
2
2
(dicarboximide) as a reference standard at room temperature (Table 2). The ΦPL increased from
BF -HP1 to BF -LP5 (Table 2). These result indicated that the concentration of light-emitting units
2
2
in the internal structure of hyperbranched polymers was higher than the linear one, thus resulting in
the fluorescence quenching to some extent [38].
To further confirm the ICT processes of these polymers, the PL spectra in different solvents
(
CH Cl , THF and DMF) with different polarity were performed (Table 2). The emission spectra
2 2
were collected with the excitation light at the peaks determined from the absorption spectra. From
CHCl , to CH Cl , to DMF, except for THF, all polymers BF -HP1-4 and BF -LP5 showed a
3
2
2
2
2
marked red-shift by increasing the solvent polarity. In addition, these solvent dependencies were
confirmed by the Lippert-Mataga plot [39-41], which showed a linear correlation of the Stokes shift
with solvent polarity (Fig. 3). These results were strongly indicative of ICT. We note that, in the case
of THF as the solvent, irregular Stokes shifts were observed which were lower than estimated.
Exactly why this should be so is not absolutely clear to us but we suggest that this was either related
5

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to the good dissolution of the polymers in THF or their hyperbranched structure. The same tendency
has also been observed in the data reported by other groups [16,42].
The spectra of BF -HP1-4 and BF -LP5 thin films prepared on quartz plates were measured (Fig.
2
2
4) and these results and their quantum yields were shown in Table 3. The absorption and emission
peaks featured a red-shift emission profile from BF -HP1 to BF -LP5, providing an opposite trend
2
2
compared with those of polymers in chloroform. In general, the three-dimensional architecture could
suppress π-π stacking in hyperbranched polymers compared to their linear counterpart, and thus the
intermolecular stacking increased along with the decrease of the degree of branching from
BF -HP1-4 to BF -LP5, accounting for the red-shift for polymers in film states. As can be seen from
2
2
Table 3, a 19 nm red-shift was observed from BF -HP1 to BF -LP5. Notably, the emission peak of
2
2
BF -HP1 in chloroform was almost the same as that of in film; whereas the emission peak of
2
BF -LP5 displayed a 45 nm red-shift from chloroform solution to film state. Taking the absorption
2
and emission spectra into consideration, one does believe that the hyperbranched architectures could
suppress the aggregation more effectively than the linear ones in the film state, consistent with the
trend in a poor solvent such as DMF.
The electrochemical properties of the hyperbranched polymers BF -HP1-4 and BF -LP5 was
2
2
recorded using cyclic voltammetry (CV), which was conducted in anhydrous methylene chloride
using tetrabutylammonium hexafluorophosphate (TBAPF ) as a supporting electrolyte with a
6
+
standard three-electrode electrochemical cell containing a Pt counter electrode, Ag/Ag as the
reference electrode, and a glass carbon working electrode. Fig. 5 shows the cyclic voltammograms of
-1
BF -HP1-4 and BF -LP5 at a scan rate of 30 mV s in the range of 0-1.7 V. The HOMO energy
2
2
ox
levels were calculated according to the following equation: HOMO = −([Eonset] + 4.4) eV. The band
gap (ꢀE) of polymers BF -HP1-4 and BF -LP5 were calculated from the UV-vis absorption onset of
2
2
the polymers. The LUMO levels were obtained on the basis of the equation: ELUMO = EHOMO + Egap.
6

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The results are summarized in Table 4. With the increase in the linear length of hyperbranched
polymer, HOMO energy levels were more negative, and the band gap became larger.
The thermal properties of the polymers BF -HP1-4 and BF -LP5 were further investigated by
2
2
thermogravimetric analysis (TGA) in a nitrogen atmosphere. As shown in Fig. 6, the onset
temperatures of 5% weight loss of these polymers were 221 °C, 223 °C, 201 °C, 226 °C, and 210 °C,
respectively, indicating that the polymers BF -HP1-4 and BF -LP5 have good thermal stability.
2
2
3
. Experimental Section
.1 General
3
Chemical reactants were purchased from Soochiral Chemical Science & Technology Co., Ltd. and
J&K Scientific Ltd. and used without further purification. Organic solvents were rigorously purified
and dried by standard methods.
The reactions were monitored by TLC with silica gel 60 F254 (Merck, 0.2 mm). Column
1
13
chromatography was carried out on silica gel (200-300 mesh). The H NMR and C NMR spectra
were measured with a 600 MHz Bruker spectrometer using tetramethylsilane as reference at 298 K.
High-resolution mass spectra (HRMS) were recorded on a Bruker solariX FTICR mass spectrometer
operating in a MALDI mode. Fourier transform infrared spectroscopy (FTIR) was tested on a
Varian-640 spectrophotometer (KBr pellet technique). The M and weight-average molecular weight
n
(
M ) were assessed using a Waters 2414 GPC equipped with Waters HT4 and HT3 column-assembly
w
−
1
and a Waters 2414 refractive index detector (eluent, THF; flow rate, 1.00 mL min ), which is
calibrated by the polystyrene standard (the M of polystyrene standard are 3790, 13000, 30300,
n
-1
5
2000, 219000 g mol ). UV-vis and fluorescence spectra were carried out on Shimadzu UV-2550
and RF5300PC spectrophotometer, respectively. Absolute fluorescence quantum yields of polymers
in film (ΦPL, film) were measured on Edinburgh FLS920 steady fluorimeter with a calibrated
integrating sphere (excited at 365 nm). The cyclic voltammetry measurement was performed on CHI
7

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630A electrochemical analyzer at room temperature at atmospheric pressure in anhydrous methylene
-1
chloride with a scanning rate of 30 mV s , having tetrabutylammonium hexafluorophosphate
(
TBAPF ) as a supporting electrolyte using a standard three-electrode electrochemical cell
6
+
containing a Pt counter electrode, acetonitrile Ag/Ag (0.01 M in CH CN) as the reference electrode,
3
and a glassy carbon working electrode. The system was calibrated with the standard
ferrocene/ferrocenium (Fc) redox system and assumption that the energy level of Fc is 4.8 eV below
vacuum. TGA measurements were carried out Pyris 1 TGA under a nitrogen atmosphere (20 mL
-1
-1
min ) at a heating rate of 20 °C min .
3.2 Synthesis of Monomers and Polymers
M1. In a 250-mL three-necked flask with a dropping funnel, a mixture of 4-bromoacetophenone
(2.40 g, 12 mmol) and NaH (0.96 g, 28 mmol) in dry THF (40 mL) was placed under an argon
atmosphere. The dry THF solution (20 mL) containing methyl 4-bromobenzoate (2.84 g, 13.2 mmol)
was added dropwise at 5 °C in an ice bath within 15 min, and the mixture was further stirred for 8 h
at 50 °C. The reaction mixture was allowed to cool down to room temperature, and 10% HCl was
then gently added until the solution color gradually turned from orange to light yellow. Water (50
mL) and ethyl acetate (200 mL) were added, and the organic layer was separated and dried over
anhydrous Na SO . After removing a large portion of the ethyl acetate under reduced pressure,
2
4
crystallisation
form
the
hot
ethyl
acetate
gave
a
plate-like
crystal
of
1
1
,3-bis(4-bromophenyl)-propane-1,3-dione (2.84 g, 62%). H NMR (600MHz, DMSO-d , δ): 16.98
6
1
3
(
s, 1H), 7.34 (s, 1H), 8.11 (d, J = 7.2 Hz, 4H), 7.85 (d, J = 7.8 Hz, 4H). C NMR (150MHz,
-1
d -DMSO, δ): 184.8, 134.1, 132.4, 131.0, 129.9, 127.6, 94.0. FTIR (KBr, cm ): 3468, 1920, 1579,
6
1
511, 1477, 1294, 1068, 1000, 775. HRMS (MALDI-TOF): Calcd. for C H Br O : m/z 382.9105,
15 11 2 2
+
found: [M+H] 382.9101.
M2. A mixture of M1 (2.0 g, 5.2 mmol), di-tert-butyl dicarbonate (5.71 g, 26.2 mmol) and DMAP
(63.4 mg, 0.52mmol ) in dry THF (80 mL) was stirred at 45 °C for 10 h under an argon atmosphere.
8

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After cooling to room temperature, the solvent was removed under reduced pressure, and
1
recrystallization from CH Cl and hexane afforded M2 as a yellowish crystal (1.35 g, 54%). H
2
2
NMR (600MHz, DMSO-d , δ): 7.83 (d, J = 8.4 Hz, 2H), 7.62 (d, J = 8.4 Hz, 2H), 7.58 (s, 1H), 7.09
6
1
3
(
s, 1H), 1.55 (s, 9H). C NMR (150MHz, DMSO-d , δ): 182.4, 151.5, 144.9, 132.5, 128.1, 127.5,
6
-
1
1
1
27.2, 125.0, 123.4, 122.9, 121.1, 104.7, 79.8, 22.9. FTIR (KBr, cm ): 3072, 2981, 1907, 1745,
664, 1600, 1481, 1301, 1238, 1145, 1079, 1002, 817. HRMS (MALDI-TOF): Calcd. for
+
C H Br O Na: m/z 504.9449, found: [M+Na] 504.9445.
20
18
2
4
Boc-HP1-4 and Boc-LP5. A mixture of the corresponding monomers and NaHCO was added to a
3
solution of THF (20 mL) and H O (4 mL). Reaction system was carefully degassed and then
2
Pd(PPh ) (3 mg) was added. The reaction mixture was heated at 80 °C with vigorous stirring for 48
3
4
h under an argon atmosphere. Bromobenzene (100 mg, 0.64 mmol) was added to end-cap the boron
containing end groups. After refluxing for another 12 h, the mixture was cooled to room temperature.
Then water (50 mL) and CH Cl (200 mL) were added, the organic layer was separated and dried
2
2
over anhydrous Na SO . After removal of most of the solvent, the resulting mixtures were
2
4
precipitated in methanol. The crude products were repurified by precipitation from THF into a large
excess of hexane again and dried under vacuum to give yellow polymers.
1
Boc-HP1: H NMR (600MHz, DMSO-d , δ): 8.75-8.31 (br, 3H), 8.3-8.05 (br, 4H), 8.05-7.38 (br,
6
1
9H), 3.01-2.88 (br, 6H), 2.31-1.98 (br, 9H), 1.48 (s, 9H), 1.02-0.67 (br, 58H). GPC: M = 56300;
w
M = 28300; polydispersity = 1.99.
n
1
Boc-HP2: H NMR (600MHz, DMSO-d , δ): 8.74-8.32 (br, 3H), 8.32-8.05 (br, 4H), 8.04-7.57 (br,
6
1
7H), 3.31-2.76 (br, 6H), 2.40-1.97 (br, 9H), 1.48 (s, 10H), 1.05-0.68 (br, 55H). GPC: M = 69400;
w
M = 28100; polydispersity = 2.47.
n
1
Boc-HP3: H NMR (600MHz, DMSO-d , δ): 8.63-8.32 (br, 3H), 8.32-8.06 (br, 5H), 8.05-7.57 (br,
6
3
0H), 3.30-2.75 (br, 6H), 2.31-1.94 (br, 12H), 1.48 (s, 9H), 1.02-0.69 (br, 54H). GPC: M = 60800;
w
M = 26700; polydispersity = 2.28.
n
9

ACCEPTED MANUSCRIPT
1
Boc-HP4: H NMR (600MHz, DMSO-d , δ): 8.63-8.34 (br, 3H), 8.29-8.04 (br, 14H), 8.03-7.47
6
(
br, 81H), 3.33-2.76 (br, 6H), 2.46-1.83 (br, 6H), 1.48 (s, 9H), 1.02-0.69 (br, 60H). GPC: M =
w
4
4100; M = 21200; polydispersity = 2.08.
n
1
Boc-LP5: H NMR (600MHz, DMSO-d , δ): 8.20-8.11 (br, 4H), 7.95-7.47 (br, 10H), 7.01 (br, 1H),
6
2
.17-1.98 (br, 10H), 1.43 (br, 9H), 1.35-1.16 (br, 10H), 0.94-0.54 (br, 18H). GPC: M = 30200; M =
w
n
1
5100; polydispersity = 2.00.
OH-HP1-4 and OH-LP5. Piperidine (3.00 ꢁL, 0.3 mmol) was added to a solution of Boc-HP1-4
or Boc-LP5 (100 mg) in CH Cl (20 mL). After stirring for 24 h at room temperature, water and
2
2
CH Cl (100 mL) were added. The organic layer was separated and washed with water three times,
2
2
dried over Na SO , and concentrated to dryness. The crude polymer was purified by precipitation
2
4
from THF into hexane and dried under vacuum to give yellow polymers.
1
OH-HP1: H NMR (600MHz, DMSO-d , δ): 17.25 (br, 1H), 8.60-8.30 (br, 3H), 8.29-8.16 (br, 3H),
6
8.03-7.59 (br, 12H), 7.06 (br, 1H), 3.11-2.93 (br, 6H), 2.30-2.00 (br, 12H), 1.03-0.75(br, 63H). GPC:
M = 105200; M = 20000; polydispersity = 5.26.
w
n
1
OH-HP2: H NMR (600MHz, DMSO-d , δ): 17.25 (br, 1H), 8.61-8.30 (br, 3H), 8.28-8.13 (br, 3H),
6
8.01-7.48 (br, 13H), 7.03 (br, 1H), 3.10-2.86 (br, 8H), 2.38-2.01 (br, 18H), 1.03-0.71(br, 63, 114H). .
GPC: M = 63900; M = 23000; polydispersity = 2.78.
w
n
1
OH-HP3: H NMR (600MHz, DMSO-d , δ): 17.25 (br, 1H), 8.64-8.29 (br, 3H), 8.27-8.06 (br, 3H),
6
8.00-7.44 (br, 17H), 7.00 (br, 1H), 3.11-2.80 (br, 5H), 2.34-1.99 (br, 8H), 1.01-0.74(br, 63, 38H). .
GPC: M = 39700; M = 18900; polydispersity = 2.10.
w
n
1
OH-HP4: H NMR (600MHz, DMSO-d , δ): 17.25 (br, 1H), 8.63-8.29 (br, 3H), 8.27-8.04 (br, 5H),
6
8.01-7.47 (br, 26H), 7.00 (br, 1H), 3.11-2.79 (br, 2H), 2.32-1.99 (br, 10H), 0.99-0.69 (br, 42H). GPC:
M = 53100; M = 18700; polydispersity = 2.84.
w
n
1
0

ACCEPTED MANUSCRIPT
1
OH-LP5: H NMR (600MHz, DMSO-d , δ): 17.10 (br, 1H), 8.20-8.10 (br, 2H), 7.94-7.47 (br,
6
1
2H), 7.01 (br,1H), 2.16-2.00 (br, 4H), 1.36-1.17 (br, 12H), 0.94-0.56 (br, 18H). GPC: M = 26900;
w
M = 13200; polydispersity = 2.80.
n
BF -HP1-4 and BF -FLP5. To a solution of OH-HP1-4 or OH-LP5 (90 mg) in CH Cl (30 mL),
2
2
2
2
borontrifluoride-ether complex (0.1 g, 0.345 mmol) was added to the reaction mixture. The resulting
mixture was stirred at room temperature for 6 h. After reaction, water and CH Cl (100 mL) were
2
2
added, and the organic layer was separated and washed with water three times, dried over Na SO ,
2
4
and concentrated to dryness. The crude polymers were precipitated from THF into a large excess of
hexane. The product was isolated by centrifugation and dried under vacuum. The resulting polymers
were obtained as a red powder.
1
BF -HP1: H NMR (600MHz, DMSO-d , δ): 8.60-8.28 (br, 6H), 8.12-7.60 (br, 11H), 7.39 (br,
2
6
1
9
1
H), 3.11-2.92 (br, 6H), 2.31-1.98 (br, 18H), 1.27 (br, 18H), 1.03-0.68 (br, 70H). F NMR (564
1
0
11
MHz, CDCl , δ): -150.65 ( BF ), -150.71 ( BF ). GPC: M = 148000; M = 18500; polydispersity
3
2
2
w
n
=
8.01.
BF -HP2: H NMR (600MHz, DMSO-d , δ): 8.81-8.28 (br, 6H), 8.03-7.75 (br, 14H), 7.39 (br,
1
2
6
1
9
1
H), 3.10-2.92 (br, 6H), 2.50-2.09 (br, 16H), 1.27 (br, 13H), 1.04-0.73(br, 54H). F NMR (564 MHz,
1
0
11
CDCl , δ): -150.62 ( BF ), -150.68 ( BF ). GPC: M = 160600; M = 21700; polydispersity = 7.40.
3
2
2
w
n
1
BF -HP3: H NMR (600MHz, DMSO-d , δ): 8.64-8.26 (br, 6H), 8.11-7.58 (br, 16H), 7.39 (br,
2
6
1
9
1
H), 3.16-2.81 (br, 5H), 2.34-1.98 (br, 12H), 1.28 (br, 6H), 1.02-0.67 (br, 40H). F NMR (564 MHz,
1
0
11
CDCl , δ): -150.60 ( BF ), -150.65 ( BF ). GPC: M = 50200; M = 18600; polydispersity = 2.69.
3
2
2
w
n
1
BF -HP4: H NMR (600MHz, DMSO-d , δ): 8.63-8.23 (br, 6H), 8.11-7.57 (br, 22H), 7.39 (br,
2
6
1
9
1
H), 3.11-2.91 (br, 4H), 2.24-1.98 (br, 10H), 1.29 (br, 3H), 1.02-0.67 (br, 30H). F NMR (564 MHz,
1
0
11
CDCl , δ): -150.63 ( BF ), -150.69 ( BF ). GPC: M = 31600; M = 18700; polydispersity = 1.69.
3
2
2
w
n
1
1

ACCEPTED MANUSCRIPT
1
BF -LP5: H NMR (600MHz, DMSO-d , δ): 8.40-8.25 (br, 2H), 7.97-7.53 (br, 12H), 7.33 (br, 1H),
2
6
1
9
2
.18-2.01 (br, 4H), 1.32-1.17 (br, 12H), 0.94-0.59 (br, 18H). F NMR (564 MHz, CDCl , δ):
3
1
0
11
-
150.66 ( BF ), -150.71 ( BF ). GPC: M = 21800; M = 12100; polydispersity = 1.80.
2
2
w
n
4.
Conclusions
In summary, we have successfully prepared a series of hyperbranched polymers (BF -HP)
2
containing difluoroboron β-diketonate and truxene units via the Pd(0)-catalyzed Suzuki coupling
reaction by an “A + B ” or “A + B + B ” approach. These organoboron-containing polymers
2
3
2
2
3
exhibited red-shifted emission compared with their uncomplexed counterparts. The optical properties
can be tuned by the hyperbranched architectures. In chloroform solution, the emission spectra
exhibited significant blue-shift with the increase of linear length in the hyperbranched architecture,
whereas a red-shift resulted in the film state, indicating that hyperbranched structure can effectively
suppress the aggregation in the solid state. Furthermore, these polymers exhibited high thermal
stability, and good solubility in common organic solvents.
Acknowledgements: Financial support by the National Natural Science Foundation of China
(21274037 and 21474026), the Natural Science Foundation of Hebei Province (B2016418005), the
Youth Foundation of Hebei Educational Committee (QN2014069) and Hebei University construction
project for comprehensive strength promotion of Midwest colleges and universities is gratefully
acknowledged.
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Scheme 1. Chemical structures of the hyperbranched polymers BF -HP(1-4).
2
1
8

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Scheme 2. Synthesis of the monomers and hyperbranched polymers BF -HP1-4.
2
1
9

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Fig. 1. GPC elution traces of polymers (a) Boc-HP1-4 and Boc-LP5, (b) BF -HP1-4
2
and BF -LP5.
2
2
0

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Fig. 2. UV-vis absorption and PL spectra of (a), (b) Boc-HP1-4 and Boc-LP5; (c), (d)
OH-HP1-4 and OH-LP5; (e), (f) BF -HP1-4 and BF -LP5 in chloroform.
2
2
2
1

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Fig. 3. Lippert−Mataga plots of the polymers obtained from the data in Table 2. ꢀf is
the orientational polarisability of solvent.
2
2

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Fig. 4. UV-vis absorption (a) and PL spectra (b) of polymers BF -HP1-4 and
2
BF -LP5 in film.
2
2
3

ACCEPTED MANUSCRIPT
Fig. 5. Cyclic voltammograms of BF -HP1-4 and BF -LP5 in anhydrous methylene
2
2
-1
chloride at a scan rate of 30 mV s .
2
4

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Fig. 6. TGA traces of BF -HP1-4 and BF -LP5.
2
2
2
5

ACCEPTED MANUSCRIPT
Table 1. The polymer weight of synthesized polymers.
yield
Td
( C)
polymers
Mn
Mw
M /M
w
n
o
(%)
Boc-HP1
Boc-HP2
Boc-HP3
Boc-HP4
Boc-LP5
28300
28100
26700
21200
15100
18500
21700
18600
18700
12100
56300
69400
60800
44100
30200
148100
160600
50200
31600
21800
1.99
2.47
2.28
2.08
2.00
8.01
7.40
2.70
1.69
1.80
44
63
62
62
53
41
57
59
58
50
-
-
-
-
-
BF -HP1
221
223
201
226
210
2
BF -HP2
2
BF -HP3
2
BF -HP4
2
BF -LP5
2
2
6

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Table 2. Photophysical properties of BF -HP1-4 and BF -LP5 in various solvents.
2
2
CHCl3
THF
CH Cl2
DMF
2
Stokes
shift
Compd λPL,max Stokes shift
λPL,max Stokes shift
λPL,max Stokes shift
λPLmax
ΦPLa
a
a
a
ΦPL
ΦPL
ΦPL
-
1
-1
-1
(nm)
(cm )
(nm)
(cm )
(nm)
(cm )
(nm)
-
1
(
cm )
BF -HP1 562
4040
4025
3944
3649
3377
0.27
0.29
0.33
0.35
0.35
535
534
532
530
528
3580
3446
3278
3234
3110
0.18
0.19
0.21
0.30
0.33
584
581
576
570
563
4903
4670
4521
4338
4168
0.10
0.13
0.15
0.21
0.23
585
586
591
592
593
4932
4674
4585
4476
4459
0.036
0.048
0.053
0.054
0.069
2
BF -HP2 560
2
BF -HP3 556
2
BF -HP4 547
2
BF -LP5 539
2
a
using N,N′-bis(1-ethylpropyl)-3,4,9,10-perylene-bis(dicarboximide) as a reference standard [43].
2
7

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Table 3. Photophysical properties of BF -HP1-4 and BF -LP5 in chloroform and film.
2
2
λabs, max, solution λabs, max, film λPL, max, solution λPL, max, film
a
Polymers
ΦPL, film
(nm)
(nm)
(nm)
(nm)
BF -HP1
458
457
456
456
456
440
441
449
486
490
562
560
556
547
539
565
567
573
576
584
0.018
0.037
0.040
0.025
0.020
2
BF -HP2
2
BF -HP3
2
BF -HP4
2
BF -LP5
2
a
Absolute quantum yield.
2
8