Facile one-pot/one-step technique for preparation of side-chain functionalized polymers: Combination of SET-RAFT polymerization of azide vinyl monomer and click chemistry

Article abstract of DOI:10.1002/pola.25868

An azido-containing functional monomer, 11-azido-undecanoyl methacrylate, was successfully polymerized via ambient temperature single electron transfer initiation and propagation through the reversible addition-fragmentation chain transfer (SET-RAFT) meth

Full text of DOI:10.1002/pola.25868

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Facile One-Pot/One-Step Technique for Preparation of Side-Chain
Functionalized Polymers: Combination of SET-RAFT Polymerization of
Azide Vinyl Monomer and Click Chemistry
Qiong Shen,1 Jian Zhang,1 Shuangshuang Zhang,1 Yigang Hao,1 Wei Zhang,1
Weidong Zhang,2 Gaojian Chen,2 Zhengbiao Zhang,1 Xiulin Zhu1
1Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering
and Materials Science, Soochow University, Suzhou 215123, China
2Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China
Correspondence to: W. Zhang (E-mail: weizhang@suda.edu.cn) or X. Zhu (E-mail: xlzhu@suda.edu.cn)
Received 26 August 2011; accepted 17 November 2011; published online 15 December 2011
DOI: 10.1002/pola.25868
ABSTRACT: An azido-containing functional monomer, 11-azido-
undecanoyl methacrylate, was successfully polymerized via
ambient temperature single electron transfer initiation and
propagation through the reversible addition–fragmentation
chain transfer (SET-RAFT) method. The polymerization behav-
ior possessed the characteristics of ‘‘living’’/controlled radical
polymerization. The kinetic plot was first order, and the molec-
ular weight of the polymer increased linearly with the mono-
mer conversion while keeping the relatively narrow molecular
weight distribution (Mw/Mn ꢀ 1.22). The complete retention of
azido group of the resulting polymer was confirmed by 1H
NMR and FTIR analysis. Retention of chain functionality was
confirmed by chain extension with methyl methacrylate to
yield a diblock copolymer. Furthermore, the side-chain func-
tionalized polymer could be prepared by one-pot/one-step
technique, which is combination of SET-RAFT and ‘‘click chem-
C
V
istry’’ methods. 2011 Wiley Periodicals, Inc. J Polym Sci Part
A: Polym Chem 50: 1120–1126, 2012
KEYWORDS: azide polymer; click chemistry; living polymeriza-
tion; radical polymerization; reversible addition-fragmentation
chain transfer (SET-RAFT)
INTRODUCTION ‘‘Click chemistry’’ is a group of chemical
reactions, which have modularity, high efficiency, simple
reaction conditions, stereospecificity, give high yields, and
produce no by-products.1 As a member of the family of click
alyst from reaction mixtures, and decreasing chance of side
reactions. Most recently, SET-RAFT, a combination of ambient
temperature SET initiation propagation through the RAFT
method, was reported.10 In SET-RAFT system, the controll-
ability of polymerization should be improved due to the
coexistence of SET–LRP and RAFT processes, even its mecha-
nism need further deep understanding. Till now, nearly all
vinyl monomers except the vinyl alkyne and azide monomer,
which can be polymerized by common free-radical polymer-
ization method, were suitable to above CRP methods. The
difficulty in controlling polymerizations of vinyl alkyne and
azide monomers stems from their sensitivities to heat and
UV light (azide monomer) or other side reactions.11 Recently,
our group reported the successful controlled polymerization
of an alkyne-containing monomers, propargyl methacrylate
(PgMA), via SET-RAFT technique.11 As for the preparation of
azide polymers, chemical modification was often used.12
However, the azide content in the polymer chain produced
by this technique is difficult to be controlled. Living cationic
ring-opening polymerization was reported to synthesize
azide polymers,13 but it required stringent reaction
reaction,
copper-catalyzed
azide-alkyne
cycloaddition
(CuAAC) has attracted much attention due to its wide appli-
cation in various research areas, including bioconjugation,2
chemical synthesis,3 materials science,4 and so on. Many
researchers reported the application of click chemistry in
polymer design since it was introduced into polymer science
area in 2004.5
‘‘Living’’/controlled radical polymerization (CRP) methods
are powerful techniques to prepare polymers with controlla-
ble architectures and properties, which include nitroxide-
mediated radical polymerization,6 atom transfer radical poly-
merization (ATRP),7 reversible addition–fragmentation chain
transfer (RAFT) polymerization,8 and single electron trans-
fer–living radical polymerization (SET–LRP).9 As a relatively
newer CRP method, SET–LRP has many advantages such as
relatively low polymerization temperature (room tempera-
ture), ultrahigh polymerization rate, easy removal of the cat-
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2011 Wiley Periodicals, Inc.
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conditions, such as high-vacuum technique and high purities
of reagents. According to the literature, the polymerizations
of azide monomers should be conducted in the absence of
UV light and at low temperature, because the azide group is
very sensitive to heat and UV light. Moreover, the side reac-
tion (cycloaddition between azide group and carbon double
bond) is prone to take place, especially at relatively high
temperature. Fortunately, Bai and coworkers14 reported sev-
eral successful low temperature systems for the controlled
free-radical polymerizations of azide monomers, including c-
ray irradiation (0 ꢁC) and redox initiator techniques.15 Bai
successfully prepared the side-chain functionalized polymers
via click chemistry based on the azide polymers; however,
two-step and two-pot reactions should be used.
Dimethyl sulphoxide (DMSO) and triethylamine (analytical
reagent, Shanghai Chemical Reagent) were dried by 4 Å mo-
lecular sieve before use. All other chemical agents were pur-
chased from Shanghai Chemical Reagent and used as
received.
Synthesis of 11-Azido Undecanol
In a 250-mL round-bottomed flask, a solution of 11-bro-
moundecanol (12.55 g, 50 mmol) in dimethylformamide
(DMF) (150 mL) was added an another solution of sodium
azide (9.75 g, 150 mmol) in water (50 mL), and the reaction
ꢁ
mixture was stirred for 24 h at 80 C. Then methylene chlo-
ride (150 mL) was added, and the solution was washed with
water (3 ꢃ 150 mL). The organic phase was dried in anhy-
drous MgSO4 overnight, filtered, and concentrated. The
obtained product was a colorless liquid (9.37 g, 88%).
Modular processes combining CuAAC and CRP techniques
have been considered to be a powerful technique to produce
functional polymers. Among the CRP techniques reported,
ATRP and SET–LRP are the best choice because CuAAC and
CRP can share the same Cu(I) catalytic system. Haddleton
and coworkers16 reported the simultaneous CuAAC and CRP
techniques to synthesize the functional polymer using PgMA
as an alkyne monomer, and the mechanism was studied in
detail. We also successfully used PgMA as the alkyne
monomer to prepare side-chain functional polymers via com-
bination of SET-RAFT and click chemistry techniques.11
Drockenmuller and coworkers17 reported preparation of
functionalized random copolymers via one-pot click chemis-
try/ATRP tandems approaches. However, the polymerization
became uncontrollable when the ratio of azide monomer
[11-azido-undecanoyl methacrylate (AzUMA)]/methyl meth-
acrylate (MMA) increased from 1:4 to 3:7. The main reason
may be due to the relatively high polymerization tempera-
ture (90 ꢁC). So, the direct CRP of azide monomer in the
presence of Cu(I) catalytic system at low temperature should
provide the chance for the one-pot/one-step preparation of
functionalized polymers.
1H NMR (CDCl3): d (ppm) 3.64 (t, CH2AOH, 2H), 3.25 (t,
CH2AN3, 2H), 1.71–1.17 (m,CH2, 18H), and the appearance
of azide signals in FTIR spectra was in 2090 cmꢄ1
.
Synthesis of AzUMA
A solution of 11-azido undecanol (8.50 g, 40 mmol), triethyl-
amine (4.85 g, 48 mmol), and anhydrous THF (100 mL) was
cooled in an ice water bath. Methacryloyl chloride (5.06 g,
48 mmol) diluted by a small amount of anhydrous THF (15
mL) was added dropwise over a period of 20 min, and the
mixture was stirred in the cooling bath for 1 h and then for
24 h at room temperature. Then water (100 mL) was added,
and the mixture was extracted with methylene chloride (3 ꢃ
100 mL). The organic layer was dried by anhydrous MgSO4,
filtered, and concentrated. The obtained crude product was
purified by flash chromatography and eluted with the mix-
ture of hexane/ethyl acetate (from 50:1 gradually increasing
to 20:1). After eluent was removed, 4.72 g (yield: 42%) of
AzUMA was obtained as a colorless liquid.
1H NMR (CDCl3): d (ppm) 6.06 (d, CHH¼¼C(CH3), 1H), 5.51
(s, CHH¼¼C(CH3), 1H), 4.10 (t, OCH2, 2H), 3.25 (t, CH2N3,
2H), 1.91 (s, CH2¼¼C(CH3), 3H), 1.71–1.17 (m, CH2, 18H). 13C
Herein, we reported a strategy for the synthesis of the well-
defined azide polymers via SET-RAFT polymerization tech-
nique at room temperature. Furthermore, a one-pot/one-step
technique combining SET-RAFT and click chemistry techni-
ques has been successfully used to synthesize the side-chain
functionalized polymers, and functionalization content of the
polymer chains was also controlled by changing the molar
ratio of azide monomer and alkyne component.
NMR (CDCl3):
d
(ppm) 166.99 (COO, 1C), 136.59
(CH2¼¼CCH3, 1C), 124.79 (CH2¼¼CCH3, 1C), 64.60 (OCH2, 1C),
51.37 (CH2N3, 1C), 29.90–25.90 ((CH2)9, 9C), 18.21
(CH2¼¼C(CH3), 1C). The appearance of azide signals in FTIR
spectra was in 2090 cmꢄ1
.
Synthesis of 4-Propargyloxy-40-Methoxy Azobenzene
In a 250-mL round-bottomed flask, 4-methoxy aniline (2.0 g,
16.3 mmol) was added to a solution of concentrated HCl
(37.0%, 4.05 g, 48.9 mmol) in water (80 mL). The mixture
was stirred in an ice bath to keep the reaction temperature
at 0–5 ꢁC. Then a water solution (10 mL) of sodium nitrite
(1.34 g, 19.4 mmol) was added dropwise within 10 min. A
brown transparent diazonium salt solution was obtained,
EXPERIMENTAL
Materials
11-Bromoundecanol (98%, Acros), propargyl bromide (80 wt
%
solution in toluene, Acros), ethyl-2-bromoisobutyrate
(EBiB; 98%, Acros), sodium azide (ꢂ99.5%; Aldrich), and
copper powder (Cu(0), <75 lm, 98%, Aldrich) were used as
received. Tetrahydrofuran (THF) was dried over sodium
overnight and distilled before use. Pentamethyldiethylenetri-
amine (PMDETA; Jiangsu Liyang Jiangdian Chemical Factory,
Liyang, China, 98%) was dried with 4 Å molecular sieve and
distilled in vacuum. 2-Cyanoprop-2-yl 1-dithionaphthalate
(CPDN) was synthesized according to the references.18
ꢁ
after reacted for 60 min at 0–5 C. Meanwhile, a coupling so-
lution was prepared as follows: phenol (1.68 g, 17.9 mmol),
sodium hydroxide (NaOH; 0.70 g, 17.9 mmol), and NaHCO3
(3.0 g, 35.8 mmol) were ꢁdissolved in 150 mL of water under
vigorous stirring at 0–5 C. Then the diazonium salt solution
was added dropwise to the coupling solution within 20 min
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ꢁ
ꢁ
at 0–5 C. The final mixture was reacted at 5 C for 3 h. The
precipitate was collected by filtration, washed with deionized
water three times, and dried under vacuum. The crude prod-
uct (4-methoxy-40-hydroxy azobenzene) was obtained as yel-
low solid (3.21 g, yield 86.7%).
mmol), CPDN (7.1 mg, 0.0516 mmol), and solvent DMF (1.5
mL) were added to a dry glass ampoule with a magnetic bar.
The reaction mixture was bubbled with argon for 10 min,
and then PMDETA (9.0 lL, 0.086 mmol) was added to the
mixture. The solution was bubbled with argon for another 5
min to eliminate the oxygen, and then the ampoule was
flame sealed under argon atmosphere and placed in the
water bath at 25 ꢁC. After 30 h, the mixture was diluted by
5-mL THF and precipitated in 200-mL methanol. The sample
was obtained by filtration and dried to constant weight
under vacuum at room temperature. The functional PAzUMA
(P2) was also prepared by similar procedures to those
described above except that the molar ratio of [AzUMA]0:
[PMA]0:[EBiB]0:[CPDN]0:[Cu(0)]0:[PMDETA]0 was 100:110:1:
3:5:5, and polymerization time is 30 h.
A solution of 4-methoxy-40-hydroxy azobenzene (1.50 g, 6.57
mmol), propargyl bromide (0.94 g, 7.88 mmol), NaOH (0.31
g, 7.88 mmol), a catalytic amount of potassium iodide, and
50 mL of acetone were prepared in a 100-mL round-bot-
tomed flask under vigorous stirring. After stirring under
reflux for 12 h at 45 ꢁC, the solution was concentrated by
rotary evaporator. The final crude product was purified by
recrystallization from ethanol to yield pure compound
4-propargyloxy-40-methoxy azobenzene (PMA) as yellow
solid (1.42 g, 81.1%).
Characterization
1H NMR (CDCl3): d (ppm) 7.87 (d, ArH, 4H), 7.10–6.95
(m, ArH, 4H), 4.77 (s, OCH2CBCH, 2H), 3.89 (s, OCH3, 3H),
2.55 (s, CBCH, 1H). 13C NMR (DMSO-d6), d (ppm): 162.11,
159.85, 147.19, 146.47, 124.77, 124.55, 115.97, 115.09,
79.43, 79.20, 56.37, 56.15.
1H and 13C NMR spectra were recorded on an INOVA 400
MHz NMR instrument using CDCl3 as solvent and tetrame-
thylsilane as the internal standard. The molecular weights
and molecular weight distributions of the polymers were
determined using a Waters 1515 gel permeation chromato-
graph (GPC) equipped with
a refractive-index detector
Typical Procedures for SET-RAFT Polymerization of
AzUMA
(Waters 2414) using HR 1 (pore size: 100 Å, 100–5000 Da),
HR 2 (pore size: 500 Å, 500–20,000 Da), and HR 4 (pore
size 10,000 Å, 50–100,000 Da) columns (7.8 ꢃ 300 mm2, 5-
lm bead size) with molecular weights ranging from 102 to 5
ꢃ 105 g/mol. THF was used as the eluent at a flow rate of
1.0 mL/min at 30 ꢁC. GPC samples were injected using a
Waters 717 plus autosampler and calibrated with PMMA
standards purchased from Waters. FTIR spectra were
recorded on a Nicolette-6700 FTIR spectrometer.
AzUMA (0.5 mL, 1.72 mmol), EBiB (2.54 lL, 0.0172 mmol),
Cu(0) (3.3 mg, 0.0516 mmol), CPDN (4.7 mg, 0.0516 mmol),
and solvent DMSO (0.5 mL) were added to a 5-mL ampoule
with a magnetic bar. The reaction mixture was bubbled with
argon for ꢅ10 min, and then PMDETA (10.8 lL, 0.0516
mmol) was added to the mixture. The solution was deoxy-
genated by bubbling with argon for 5 min, and then the am-
poule was flame sealed under argon atmosphere and placed
in the water bath at 25 ꢁC. At the designed time, the am-
poule was opened, and the contents were diluted with about
3.0 mL THF and passed through a small neutral Al2O3 chro-
matographic column to remove any unreacted Cu(0) catalyst
and Cu(II) compounds. The resulting solution was precipi-
tated in 200 mL of methanol. The polymers were obtained
by filtration and dried to constant weight under vacuum at
room temperature. The conversion of the monomer was
determined by gravimetry.
RESULTS AND DISCUSSION
SET-RAFT Polymerization of AzUMA
14
According to Refs.
and 15, temperature is considered as a
crucial factor to decide whether the polymerization of vinyl
azide monomer proceeds successfully, because azido group
is prone to undergo cycloaddition to carbon double bond at
high temperature. The low temperature (room temperature
or lower than room temperature) used in SET–LRP system
fits the requirement; therefore, we used it to conduct the po-
lymerization of azide monomer, AzUMA.
Chain Extension of PAzUMA Using PAzUMA as a
Macroinitiator
SET-RAFT polymerization of AzUMA was carried out at room
temperature using EBiB as the initiator, CPDN as the chain
transfer agent (CTA), and Cu(0)/PMDETA as the catalyst sys-
tem. The effects of three factors (the concentrations of
monomer, CPDN, and solvent) on the polymerization were
investigated as presented in Table 1. From Table 1 (entry 1),
we can see that the polymerization was uncontrollable, and
the molecular weight distribution (Mw/Mn) of the obtained
azide polymer reached 1.92 after 3 h in the absence of
CPDN. Most interestingly, the polymerization of AzUMA can
be well controlled when CPDN, the CTA, was added. With the
increase of ratios of CPDN (keeping molar ratio of monomer
and catalyst system constant), the Mw/Mn of the obtained
polymers decreased from 1.36 to 1.19, which demonstrated
the improvement of controllability of the polymerization.
Poly(AzUMA) (PAzUMA; Mn(GPC) ¼ 7680 g/mol, Mw/Mn
¼
1.20) was used as a macroinitiator to synthesize PAzUMA-b-
poly(MMA) (PMMA) block copolymer with MMA as the sec-
ond monoꢁmer in DMF solution. The reaction was also carried
out at 25 C ([MMA]0:[EBiB]0:[PAzUMA]0:[Cu(0)]0:[PMDETA]0
¼ 200:1:3:3:3, MMA/DMF ¼ 1/5, v/v). The reaction was
stopped after 20 h, and the other procedures were similar to
those mentioned above.
Preparation of Functional PAzUMA Via One-Pot and
One-Step Technique
A
typical procedure for the preparation of functional
PAzUMA (P1) via one-pot and one-step technique is as fol-
lows: AzUMA (0.25 mL, 4.19 mmol), PMA (0.115 g, 2.09
mmol), EBiB (1.27 mL, 0.0172 mmol), Cu(0) (2.8 mg, 0.086
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TABLE 1 The SET-RAFT Polymerization Results of AzUMA at 25 8C Under Various Conditions
Entry
Polymerization Ratioa
Solvent
Time (h)
Conv. (%)
Mn(th) (g/mol)
Mn(GPC) (g/mol)
Mw/Mn
1
2
3
4
5
6
7
a
100:1:0:3:3
100:1:1:3:3
100:1:3:3:3
100:1:5:3:3
50:1:3:3:3
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
3
3
3
3
3
3
4
94.3
59.7
70.9
75.2
84.9
52.5
70.2
26,490
8,390
4,980
3,520
2,980
3,680
6,570
38,190
20,690
10,390
6,680
7,130
8,530
9,260
1.92
1.36
1.21
1.19
1.19
1.18
1.21
100:1:3:3:3
100:0:3:3:3
DMSO
Polymerization ratio: [AzUMA]0:[EBiB]0:[CPDN]0:[Cu(0)]0:[PMDETA]0.
Furthermore, the molecular weight of the polymer can also be
adjusted by changing the amount of CPDN in this system. The
similar polymerization behavior was also observed in our pre-
vious reported system.11 In addition, the polymerization rate
increased when we changed the molar ratios of monomer and
CPDN from 100:1 to 100:5 (entries 2–4), which was opposite
to the RAFT mechanism. The reason may be due to conjunc-
tion of retardation effect19 and the increase of initiator con-
centration. The retardation effect means that the increase of
CTA agent concentration would cause the decrease of poly-
merization rate. On the contrary, the increase of initiator con-
centration will cause the rate enhancement. In the current
system, the increase of initiator concentration is dominant
when compared with the retardation effect. Furthermore, the
polymerization rate decreased when the molar ratios of
monomer and CPDN were changed from 50:3 to 100:3
(entries 3 and 5). Klumperman and coworkers20 and our
group21 also reported the similar results. The polymerization
of AzUMA in DMF (another classical solvent for SET–LRP) was
also investigated, and the result was favorable (Table 1, entry
6, Mw/Mn ¼ 1.18). Interestingly, the living/controlled nature
of polymerization was still observed even in the absence of
EBiB (Table 1, entry 7, Mw/Mn ¼ 1.21). We reported the simi-
lar results previously.22 From these results, we considered
that CPDN may play two roles simultaneously in the polymer-
ization approach, a pseudohalide alkyl initiator and a CTA,
which was identical to our previous results.21
concentration of AzUMA, CPDN, and EBiB, respectively. MM is
the molecular weight of AzUMA and Conversion is the AzUMA
conversion. All of the above results indicated that SET-RAFT
polymerization of AzUMA showed the nature of CRP.
The kinetic plot for the SET-RAFT polymerization of AzUMA
was shown in Figure 1(a). A linear relationship between
ln([M]0/[M]) and polymerization time was observed, indicat-
ing a constant radical concentration throughout the polymer-
ization process. As given in Figure 1(b), the molecular weight
of the obtained PAzUMA measured by GPC (Mn(GPC)
increased linearly with monomer conversion, while keeping
the relatively low molecular weight distributions (Mw/Mn
)
ꢀ
1.22) even up to relatively high monomer conversion
(88.3%). Moreover, GPC curves of PAzUMAs also showed
unimodal and normal distributions as presented in Figure 2.
However, the molecular weight (Mn(GPC)) was higher than the
theoretical value (Mn(th)), which indicated the initiator
efficiency was not high. Mn(th) was calculated from the fol-
FIGURE 1 (a) Kinetic plots of SET-RAFT polymerization of
AzUMA in DMSO solution at 25 ꢁC. Polymerization conditions:
[AzUMA]0:[EBiB]0:[CPDN]0:[Cu(0)]0:[PMDETA]0
¼
100:1:3:3:3
and AzUMA/DMSO ¼ 1/1 (v/v); (b) the dependence of the mo-
lecular weights and molecular weight distributions on the
monomer conversions for the SET-RAFT polymerization of
AzUMA. Polymerization conditions are the same as in (a).
lowing equation, Mn(th) ¼ [M]0/([CTA]0 þ [RX]0) ꢃ MM
ꢃ
Conversion, where [M]0, [CTA]0, and [RX]0 are the initial
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FIGURE 4 GPC curves of polymers before and after chain exten-
sion with PAzUMA as the macroinitiators. Conditions: [MMA]0:[E-
BiB]0:[PAzUMA]0:[Cu(0)]0:[PMDETA]0 ¼ 200:1:3:3:3, MMA/DMF ¼
1/5 (v/v), t ¼ 20 h, T ¼ 25 ꢁC, and conversion (%) ¼ 99%.
FIGURE 2 GPC traces of PAzUMA prepared by SET-RAFT poly-
merization at 25 ꢁC. Polymerization conditions: [PAzUMA]0:[E-
BiB]0:[CPDN]0:[Cu(0)]0:[PMDETA]0 ¼ 100:1:3:3:3 and PAzUMA/
DMSO ¼ 1/1 (v/v).
methylene protons of the ethyl ester unit in the initiator
EBiB, which revealed that the initiator EBiB moieties were
successfully attached to the polymer chain ends. The signals
at d ¼ 7.35–8.25 ppm (d, e, f, and g in Fig. 3) were attrib-
uted to the aromatic protons of the naphthalene units of
CPDN, which showed that the dithiocarbonate moieties in
CPDN were also attached to the polymer chain ends. A
chain-extension experiment was also conducted to verify the
Analysis of Chain-End and Chain-Extension Experiment
The chain end of the PAzUMA sample prepared by SET-RAFT
polymerization was analyzed by 1H NMR spectra, and the
result was shown in Figure 3. The signals at d ¼ 3.24 ppm
(a in Fig. 3) represented the methylene group next to the
azido monomer unit, and the signals at d ¼ 3.90 ppm (b in
Fig. 3) were assigned to the methylene group next to the ox-
ygen of the ester group. The 1:1 ratio of the corresponding
integration values for a and b peaks in Figure 3 suggested
that azido groups were kept intact after polymerization. The
peak at d ¼ 4.12 ppm (c in Fig. 3) corresponded to the
FIGURE 5 1H NMR spectra of copolymer (P1: Mn(GPC) ¼ 21,400 g/
mol, Mw/Mn ¼ 1.30) and homopolymer (P2: Mn(GPC) ¼ 15,120 g/
mol, Mw/Mn ¼ 1.19) synthesized by one-pot and one-step tech-
nique. Reaction conditions: P1: [AzUMA]0:[PMA]0:[EBiB]0:
[CPDN]0:[Cu(0)]0:[PMDETA]0 ¼ 100:50:1:3:5:5, AzUMA/DMF ¼ 1/6
(v/v), T ¼ 25 ꢁC, and conversion (%) ¼ 97.5%; P2: [AzUMA]0:
FIGURE 3 1H NMR spectrum of PAzUMA (Mn(GPC) ¼ 8550 g/
mol, Mw/Mn ¼ 1.21) prepared via SET-RAFT polymerization with
EBiB as the initiator and CPDN as the RAFT agent. Polymeriza-
tion conditions: [AzUMA]0:[EBiB]0:[CPDN]0:[Cu(0)]0:[PMDETA]0
¼
[PMA]0:[EBiB]0:[CPDN]0:[Cu(0)]0:[PMDETA]0
¼
100:110:1:3:5:5,
100:1:3:3:3, t ¼ 1 h, T ¼ 25 ꢁC, and AzUMA/DMSO ¼ 1/1 (v/v).
AzUMA/DMF ¼ 1/12 (v/v), T ¼ 25 ꢁC, and conversion (%) ¼ 72.7%.
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living nature of obtained polymer (Fig. 3). As presented in
Figure 4, there was an apparent peak shift from the macroi-
nitiator with Mn(GPC) ¼ 7680 g/mol and Mw/Mn ¼ 1.20 to
the chain-extended PAzUMA-b-PMMA with Mn(GPC) ¼ 29,630
g/mol and Mw/Mn ¼ 1.51, respectively. All the above results
proved the functionality and feature of the living/controlled
polymerization of AzUMA.
Preparation of Functional Polymer Via One-Pot and One-
Step Technique
Because Cu(I) as the catalyst for click chemistry could be
generated in situ from the Cu(0)/PMDETA system in SET-
RAFT system, functional side-chain polymer could be pre-
pared via one-pot and one-step technique in current system.
The approaches involved SET-RAFT polymerization of AzUMA
and simultaneous coupling of PMA by click chemistry reac-
tion. Two kinds of functional polymers with different func-
tionalities could be obtained by changing the molar ratios of
AzUMA and PMA unit. The results were shown in Figures 5
and 6. As represented in Figure 5(a), when [AzUMA]0/
[PMA]0 was 1:0.5, the chemical shifts at 3.23 ppm (e) was
the characteristic peak of AzUMA unit, and the chemical
shifts of PMA at around 5.24 (d), 6.98, 7.07, and 7.86 ppm
also appeared in P1. In addition, the peak of triazole ring
emerged at 7.64 ppm (c). These results indicated that P1
still contained the azido group and PMA units also coupled
into the polymer backbone successfully via click chemistry.
As [AzUMA]0/[PMA]0 was 1:1.1, the signal at d ¼ 3.23 ppm
[e in Fig. 5(a)] disappeared completely in Figure 5(b), but
the other signals still existed. This proved that the obtained
polymer was a homopolymer and click reaction was success-
ful. Furthermore, in the FTIR spectra (Fig. 6), the strong
absorption peak at 2100 cmꢄ1 was ascribed to the azido
group [Fig. 6(a)], which meant the azido group still existed
in P1 chain. However, in Figure 6(b), the absorption peak at
2100 cmꢄ1 disappeared completely indicating the comple-
tion of the click chemistry reaction.
FIGURE 7 GPC curves of polymers (P1 and P2) prepared by one-
pot/one-step technique. Reaction conditions: P1: [AzUMA]0:[PMA]0:
[EBiB]0:[CPDN]0:[Cu(0)]0:[PMDETA]0
¼
100:50:1:3:5:5, AzUMA/
DMF ¼ 1/6 (v/v), and T ¼ 25 ꢁC; P2: [AzUMA]0:[PMA]0:[EBiB]0:
[CPDN]0:[Cu(0)]0:[PMDETA]0
¼ 1/12 (v/v), and T ¼ 25 ꢁC.
¼
100:110:1:3:5:5, PAzUMA/DMSO
polymers had monomodal distributions with relatively low
molecular weight distributions (P1: Mn(GPC) ¼ 21,400 g/mol,
Mw/Mn ¼ 1.30; P2: Mn(GPC) ¼ 15,120 g/mol, Mw/Mn ¼ 1.19)
as given in Figure 7. Hence, the successful one-pot and one-
step technique can facilitate the synthesis of side-chain func-
tional polymers and has many advantages, such as avoidance
of complex purification of precursors, less synthetic steps,
high efficiency, and so on.
CONCLUSIONS
In summary, SET-RAFT polymerization of azide monomer,
AzUMA, was achieved at room temperature in the presence of
CTA (CPDN). The polymerization was a living/controlled proce-
dure, and azide group can be kept intact after polymerization.
The functional polymers with different functional content were
also successfully synthesized via one-pot/one-step method,
which combined SET-RAFT and click chemistry techniques.
Therefore, the click reaction was quantitative, and the func-
tional content could be well controlled by adjusting the
molar ratios of [AzUMA]0 and [PMA]0. Moreover, the GPC
curves of the obtained polymers also showed that these two
The financial support from the National Nature Science Foun-
dation of China (Nos. 20874069, 50803044, 20974071,
20904036, 21004042, and 21104052), the Specialized
Research Fund for the Doctoral Program of Higher Education
contract grant (No. 200802850005), the Suzhou Project of
Applied and Fundamental Research (No. SYG201111), the Qing
Lan Project, the Program of Innovative Research Team of Soo-
chow University and the Pre-research Project of Soochow Uni-
versity, and a Project Funded by the Priority Academic Program
Development of Jiangsu Higher Education Institutions (PAPD)
are gratefully acknowledged.
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