Synthesis of hyperbranched aromatic poly(ether sulfone) with sulfonyl chloride terminal groups

Article abstract of DOI:10.1246/cl.2006.1196

A new hyperbranched aromatic poly(ether sulfone) with sulfonyl chloride terminal groups was prepared by polycondensation of a new AB₂ monomer (1), 4,4′-(m-phenylenedioxy)-bis(benzenesulfonyl chloride). The polymerization was carried out in nitr

Full text of DOI:10.1246/cl.2006.1196

1196
Chemistry Letters Vol.35, No.10 (2006)
Synthesis of Hyperbranched Aromatic Poly(ether sulfone)
with Sulfonyl Chloride Terminal Groups
Kazuya Matsumoto and Mitsuru Uedaꢀ
Department of Organic and Polymeric Materials, Graduate School of Science and Engineering,
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552
(Received July 4, 2006; CL-060753; E-mail: mueda@polymer.titech.ac.jp)
A new hyperbranched aromatic poly(ether sulfone) with sul-
fonyl chloride terminal groups was prepared by polycondensa-
tion of a new AB2 monomer (1), 4,40-(m-phenylenedioxy)-
bis(benzenesulfonyl chloride). The polymerization was carried
out in nitrobenzene at 120 ꢁC for 3 h in the presence of a catalytic
amount of FeCl3, giving the polymer with number-average
molecular weights up to 35,700. Furthermore, an ABA block
copolymer was prepared from a linear polymer, poly(ether sul-
fone) with sulfonyl chlorides at both ends and AB2 monomer 1.
SO3Na
O
O
SO3Na
SO3Na
K2CO3
HO
OH
+
Sulfolane, Toluene
240 oC, 20 h
F
O
O
SO2Cl
POCl3
130 oC, 6 h
SO2Cl
1
Scheme 1. Synthesis of AB2 monomer 1.
Recently, proton exchange membranes (PEMs) have attract-
ed much attention due to their great promise for applications
such as automotive, stationary, and portable power, where
Nafion (DuPont) and sulfonated aromatic polymers such as,
poly(ether sulfone)s, poly(ether ketone)s, polyimides, and poly-
(phenylene ether) containing sulfonic acids have been extensive-
ly studied.1
SO2Cl
O
O
SO2Cl
SO2Cl
FeCl3 1 wt %
Nitrobenzene
O
O
S
O
H
Cl
O
n
2
Hyperbranched polymers are new interesting materials with
their unique properties, such as inherent globular structure, low
viscosity, high solubility, and large number of terminal function-
al groups. There have been many reports on the synthesis and
characterization of hyperbranched polymers, and various appli-
cations such as blend components, nanoforms, nonlinear optics,
and catalysts.2 Few papers, however, have been published on
potential application of hyperbranched polymers to PEMs.
Kakimoto et al. reported the synthesis of hyperbranched poly-
mers with sulfonic acid derivatives,3 where hyperbranched aro-
matic poly(ether sulfone) having sulfonic acid terminal groups
was prepared by polycondensation of 2,6-bis(p-sodio sulfophen-
oxy)benzonitrile using a mixture of phosphorus pentoxide
and methanesulfonic acid. The cyano group on phenyl ring,
however, deactivates the reactivity of the monomer to electro-
philic sulfonylation, and is converted to a carboxylic acid. Thus,
more reactive, straightforward AB2 monomer is required for the
application of their hyperbranched polymers to PEMs.
This paper describes the synthesis of hyperbranched aromat-
ic poly(ether sulfone) with sulfonyl chloride terminal groups by
polycondensation of a new AB2 monomer, 4,40-(m-phenylene-
dioxy)bis(benzenesulfonyl chloride) (1) using a catalytic amount
of FeCl3. And its application to the synthesis of an ABA block
copolymer is described here as well.
The synthetic route for monomer 1 is outlined in Scheme 1.
Reaction of resorcinol with sodium p-fluorobenzenesulfonate in
the presence of potassium carbonate produced 4,40-(m-phenyl-
enedioxy)bis(benzenesulfonicacid disodium salt), which was
treated with phosphorus oxychloride to give monomer 1.4 The
structure of 1 was assigned on the basis of elemental analysis
as well as IR and NMR spectroscopy.4
Scheme 2. Synthesis of hyperbranched aromatic poly(ether sul-
fone) with sulfonyl chloride terminal groups 2.
Table 1. Synthesis of hyperbranched polymer 2
Temperature Time
/ꢁC
Yield
/%
a
a
b
Run
Mn
Mw=Mn
ꢀinh
/h
1
2
3
100
110
120
3
3
3
13000
22600
35700
1.5
2.0
3.7
78
88
85
0.082
0.115
0.229
aDetermined by GPC eluted with DMF containing lithium
bromide (0.01 mol/L) using polystylene standards. Measured
b
at a concentration of 0.5 g/dL in DMAc at 30 ꢁC.
presence of 1 wt % of FeCl3 to 1 (Scheme 2).5
The results are summarized in Table 1. The polymerization
proceeded smoothly at 120 ꢁC for 3 h, giving hyperbranched
polymer 2 with number-average molecular weights up to
35,700, which were determined by GPC using polystyrene stand-
ards. These polymers showed typical low solution viscosities
around 0.1–0.2 dL gꢂ1
.
The structure of hyperbranched polymer 2 was confirmed
by IR and NMR spectroscopy. The IR spectrum of 2 exhibited
characteristic absorptions at 1184 and 1369 cmꢂ1 due to the
SO2 stretching and at 1223 cmꢂ1 due to the C–O–C stretching.
All signals of polymer 2 in the 1H NMR spectrum were well
assigned to the corresponding structure of the repeating unit.
Polymer 2 is obtained as a light yellow solid, which is soluble
in nitrobenzene, tetrahydrofuran, and polar aprotic solvents
while insoluble in methanol, ethyl acetate, and acetone.
The thermal stability of polymer 2 was examined by thermo-
Polycondensation of 1 was carried out in nitrobenzene in the
Copyright Ó 2006 The Chemical Society of Japan

Chemistry Letters Vol.35, No.10 (2006)
1197
Mw=Mn changed from 1.5 to 4.9 with the addition of monomer
1. And the Mn increased from the Mn of polymer 3 with increas-
ing of amounts of monomer 1, where the GPC curves kept unim-
odal features. These results indicate the formation of the desired
ABA block polymers. ABA-block copolymers were soluble in
nitrobenzene and aprotic solvents at room temperature, and the
10% of weight-loss temperatures were approximately 380 ꢁC.
In summary, new monomer 1 was designed and synthesized.
Hyperbranched polymer 2 with number-average molecular
weights up to 35,700 was successfully prepared from monomer
1 in the presence of a catalytic amount of FeCl3. Monomer 1
was also applied for the synthesis of ABA block copolymer 4.
Polymer 4 will be applied to PEMs by hydrolysis of its sulfonyl
chlorides.
3
ClO S
SO Cl
2
PES
2
O
S
O
O
S
O
PES =
O
O
m
O
O
SO Cl
2
SO Cl
2
Nitrobenzene, FeCl
3
O
O
S
O
SO
2
Cl
O
PES
4
ClO S
2
SO Cl
2
n
O
O
S
O S
2
Cl
O
O
n
References and Notes
1
Scheme 3. Synthesis of ABA block copolymer 4.
M. A. Hickner, H. Ghassemi, Y. S. Kim, B. R. Einsla, J. E.
McGrath, Chem. Rev. 2004, 104, 4587.
2
For recent reviews, see: a) S. M. Grayson, J. M. J. Frechet,
Chem. Rev. 2001, 101, 3819. b) M. Jikei, M. A. Kakimoto,
J. Polym. Sci. Part A: Polym. Chem. 2004, 42, 1293. c) C.
Gao, Prog. Polym. Sci. 2004, 29, 183. d) B. Voit, J. Polym.
Sci. Part A: Polym. Chem. 2005, 43, 2679.
a) M. Takeuchi, M. Jikei, M. A. Kakimoto, Chem. Lett. 2003,
32, 242. b) M. Takeuchi, M. Jikei, M. A. Kakimoto, High
Perform. Polym. 2003, 15, 219.
18000
16000
14000
3
4
12000
10000
8000
6
4
2
0
To a 100-mL round bottom flask equipped with a Dean
stark apparatus and a reflux condenser was added sodium
P-fluorobenzenesulfonate (2.9 g, 14 mmol), resorcinol
(0.66 g, 6.0 mmol), potassium carbonate (2.5 g, 18 mmol),
sulfolane (24 mL), and toluene (20 mL). The reaction
mixture was heated to 150 ꢁC for 2 h, then at 240 ꢁC for
20 h, and poured into dichloromethane. The precipitate was
dissolved in hydrochloric acid solution. The filtrate was ad-
justed to pH 10 by adding sodium hydroxide solution. To this
solution was added NaCl to precipitate 4,40-(m-phenylene-
dioxy)bis(benzenesulfonicacid disodium salt). It was recrys-
tallized from ethanol and water. This salt was treated with
POCl3 (3 mL) at 130 ꢁC for 6 h. The reaction mixture was
poured in ice-water and extracted with dichloromethane.
The product was purified using column chromatography
(with 3:2 hexane:dichloromethane solvent mixture). Mono-
mer 1 was a viscous liquid. Yield (1.58 g; 57%). IR (NaCl,
ꢁ); 1184, 1377 (–SO2Cl), 1242 (Ar–O–Ar), 1477, 1577
cmꢂ1 (Ph–H). 1H NMR (CDCl3, ꢂ, ppm): 6.89 (s, 1H),
7.02 (d, 2H), 7.15 (d, 4H), 7.51 (t, 1H), 8.03 (d, 4H). Anal.
(C18H12Cl2O6S2): Calcd: C, 47.07%; H, 2.63%; Found: C,
47.06%; H, 2.79%.
0
0.5
1
1.5
2
2.5
Amount of AB2 monomer [mmol]
Figure 1. Relationship between the Mn of ABA block copoly-
mers 4 and amount of monomer 1, where 0.07 mmol of polymer
3 was used.
gravimetry. The 10% weight loss temperature was 320 ꢁC under
nitrogen.
The synthesis of a well-defined block copolymers with
sulfonated and unsulfonated blocks is important to increase
proton conductivity without massive increases in water swelling.
Thus, monomer 1 was used for the synthesis of an ABA block
copolymer (4) consisting of a linear polymer and a hyper-
branched polymer (Scheme 3).
The linear polymer, poly(ether sulfone) (3) with a number-
average molecular weight (Mn) of 9400 was prepared by poly-
condensation of 4,40-oxybis(benzenesulfonyl chloride) with
diphenyl ether in the presence of a catalytic amount of FeCl3
in nitrobenzene at 110 ꢁC for 4 h. Then, to this polymer solution,
the solution of monomer 1 and 1 wt % of FeCl3 in nitrobenzene
was added dropwise slowly over 2 h at 110 ꢁC, and stirred at this
temperature for 1 h.
5
A solution of 1 (0.30 g, 0.65 mmol), nitrobenzene (2 mL),
and FeCl3 (0.003 g, 0.018 mmol) was stirred at 110 ꢁC
for 3 h. The solution was cooled to room temperature, and
poured into methanol containing a small amount of concd
hydrochloric acid solution. The precipitate was washed with
methanol, dried at 80 ꢁC under vacuum. Yield (0.23 g, 88%).
IR (KBr, ꢁ); 1184, 1369 (–SO2Cl), 1223 (Ar–O–Ar), 1473,
1577 cmꢂ1 (Ph–H).
Figure 1 shows the relations between the Mn of resulting
ABA block copolymers and the amount of monomer 1, and
the change of molecular weight distribution (Mw=Mn). The
Published on the web (Advance View) October 5, 2006; doi:10.1246/cl.2006.1196