Zhou et al.
FULL PAPER
water and dried with anhydrous sodium sulfate over-
night, finally distillated under vacuum. Cuprous bro-
mide (CuBr, 98.5%; Sinopharm Chemical Reagent Co.,
Ltd) was purified in acetic acid, washed with methanol
and dried under vacuum to afford a white powder.
N,N,N',N'',N''-Pentamethyldiethylenetriamine (PMDETA),
its own accord. The crude product was isolated by
evaporating the solvent, and purified by using recrystal-
lization from the mixture solution of ethanol-water. H
1
NMR (300 MHz, DMSO-d
6
) δ: 8.22 (d, J=7.1 Hz, 2H),
7.70 (dd, J=16.2, 8.6 Hz, 4H), 7.35 (d, J=8.4 Hz, 2H),
13
6.76 (d, J=9.0 Hz, 2H), 3.02 (s, 6H), 2.07 (s, 6H); C
NMR (75 MHz, DMSO-d ) δ: 187.91, 169.82, 153.91,
4'-hydroxyacetophenone, 4-dimethylaminobenzaldehyde,
6
2
-bromo-2-methylpropionyl bromide (97%; Alfa Aesar)
152.45, 145.95, 136.84, 131.36, 130.52, 121.92, 116.30,
112.30, 57.39, 30.45.
were used as received. All other reagents and solvents
were analytically pure and used as received.
Synthesis of polymer St was initiated by APPBr
as the following procedure: St (2.08 g, 20 mmol), ini-
tiator (4.15 mg, 0.01 mmol), CuBr (1.43 mg, 0.01 mmol)
and PMDETA (3.46 mg, 0.02 mmol) were dissolved in
cyclohexanone and the mixture was placed into a
two-neck round-bottomed flask. The flask was sealed
and cycled between vacuum and argon for three times.
Samples were taken out by a syringe at different time
intervals and diluted with tetrahydrofuran (THF). The
diluted solution was passed through an alumina column
to remove the copper catalyst, and the filtrate was pre-
cipitated by addition of methanol. The precipitation was
filtrated and dried under vacuum. The conversion of
styrene was determined by gravimetry.
Instrument and physical measurements
1
13
H NMR and C NMR spectra were measured by
INOVA 300 MHz NMR spectrometer, CDCl or
DMSO-d as solvent and tetramethylsilane (TMS) as the
internal standard at ambient temperature. The purity was
determined with a Waters515 HPLC apparatus: a mix-
ture of methanol and water (methanol∶water=80∶20,
V∶V) was used as the eluent at a flow rate of 0.8
mL•min at 30 ℃ with a C18 column and with a Wa-
ters 996 detector. Molecular weights and the polydis-
persity (PDI) relative to PS were measured using Wa-
ters1515 GPC with THF as a mobile phase at a flow rate
of 1 mL•min and with column temperature of 30 ℃.
UV-Vis absorption spectra of the polymers and initiator
in DMF solutions were determined on a Shimadzu
RF540 spectrophotometer. Room temperature emission
and excitation spectra were carried out using Edin-
burgh-920 fluorescence spectra photometer.
3
6
−1
−1
Results and Discussion
ATRP of St initiated by APPBr
The preparation of initiator and polymer was pre-
sented in Scheme 1. Initiator is easy to dissolve in
common organic solvents such as acetone, THF, DMF,
etc. The ATRP of St was carried out using APPBr as
General reaction procedure
Synthesis of initiator 1 Initiator is prepared in two
initiator in cyclohexanone at 80 ℃ with [St] ∶
0
13
steps and characterized by H NMR and C NMR.
[APPBr] ∶[CuBr] ∶[PMDETA] =2000∶1∶1∶2,
0
0
0
−1
Synthesis of 3-(4-(dimethylamino)phenyl)-1-(4-
hydroxyphenyl)prop-2-en-one (APPO) The solution
of acetic acid (60 mL) containing 4-dimethylaminoben-
zaldehyde (2.98 g, 20 mmol) was added into the solu-
tion of sulfuric acid (2 mL) including 4'-hydroxyaceto-
phenone (2.72 g, 20 mmol). The obtained mixture was
stirred at room temperature for 24 h, and was poured
into the ice-water. The pH of the solution was adjusted
to neutral with 0.1 mol•L− NaOH. The crude powder
was collected by filtration. The pure powder (3.76 g, 14
mmol) was recrystallized from the mixture solution of
ethanol and water. Yield 70%; H NMR (300 MHz,
DMSO-d
7
Hz, 2H), 6.74 (d, J=8.5 Hz, 2H), 3.00 (s, 6H).
Synthesis of 4-(3-(4-(dimethylamino)phenyl)acryloyl)
phenyl-2-bromo-2-methylpropanoate (APPBr) APPO
[St] =0.5 mol•L and the results are shown in Figure 1
0
and Figure 2. According to Figure 1, the linearity of the
semilogarithmic plot of ln([M] /[M]) versus the polym-
0
erization time indicated that the polymerization was
first-order with respect to monomer. The number aver-
age molecular weights (M s) increase inearly with the
n
conversion and the PDIs keep relatively narrow in all
cases (M /M =1.19-1.22), indicating the polymeriza-
w
n
1
tion is well-controlled (Figure 2). The Mn(GPC)s were
similar to the corresponding Mn(th)s, in which the Mn(th)
w initiator
was calculated according to Mn(th) = M , ([St]0/
1
0
w St
w nitiator
[initiator] )×M , ×Conversion (M , and Mw,St
6
) δ: 10.30 (s, 1H), 8.02 (d, J=8.5 Hz, 2H),
are the total molecular weight of initiator and St, and
[St] and [initiator] mean the initial concentrations of St
.68 (d, J=8.7 Hz, 2H), 7.61 (s, 2H), 6.87 (d, J=8.6
0
0
and initiator, respectively). The GPC chromatograms
(Figure 3) displaying narrow, single peaks demonstrate
that there are no low molecular weight trails indicative
of transfer processes.
(
2.67 g, 10 mmol) in THF (20 mL) was placed into a 50
mL round-bottom flask with triethylamine (2.0 g, 20
mmol). The reaction mixture was cooled to 0 ℃ in an
ice/water bath and 2-bromopropionyl bromide (3.45 g,
Characterization of polymerization
According to the mechanism of ATRP, initiator
group is incorporated at α-end of the polymer chain,
while ω-end remains a terminal halide. It can be verified
1
5 mmol) in THF (10 mL) was added to a 50 mL pres-
sure equalizing addition funnel fitted to the flask. After
being added dropwise, the reaction mixture was stirred
overnight and allowed to warm to room temperature of
1
by H NMR spectrum (Figure 4). Signals at δ 8.00-
7.50 are attributed to partial of the protons in initiator
574
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Chin. J. Chem. 2014, 32, 573—578