Macromolecules
Article
purification. The pentafluorophenyl-(4-phenylthiocarbonylthio-4-
cyanovalerate) was synthesized according to a previous report.38 All
other chemicals were commercially available and used without further
purification unless otherwise stated.
The organic layer was dried with MgSO4. The solution was evaporated
to give 4-acetoxyphenyl methylsulfide as pale yellow solid. Yield: 5.9 g
(32.6 mmol, 91.3%). H NMR (CDCl3, 300 MHz) δ (ppm): 7.25 (d,
J = 8.9 Hz, 2H), 7.00 (d, J = 8.9 Hz, 2H), 2.45 (s, 3H), 2.26 (s, 3H).
13C NMR (CDCl3, 75 MHz) δ (ppm): 169.47, 148.37, 135.67, 127.97,
122.03, 21.07, 16.44.
1
1
Instruments. All H and 13C NMR spectra were recorded on a
Bruker 300 MHz FT-NMR spectrometer in deuterated solvents and
chemical shifts (δ) were given in ppm as solvent peak as internal
standard. 19F NMR spectra were recorded on a Bruker 400 MHz FT-
NMR spectrometer in deuterated solvents. The size exclusion
chromatography (SEC) was performed at room temperature using a
Jasco high performance liquid chromatography (HPLC) system (PU-
1580 Intelligent HPLC pump, RI-1530 Intelligent RI detector, AS-
1555 Intelligent HPLC autosampler, and DG-2080-53 degasser)
equipped with three MZ Analysetechnik MZ-Gel SDplus columns in
THF at a flow rate of 1.0 mL min−1. The number-average molecular
weight (Mn) and polydispersity (Mw/Mn) of the polymers were
calculated on the basis of a polystyrene calibration. IR spectra were
recorded on a Bruker Vector 22 FT-IR spectrometer using an ATR
unit.
Synthesis of Stimuli-Responsive Activated Ester Mono-
mer. Synthesis of 4-Acryloxyphenyl Methylsulfide. To the CH2Cl2
solution (30 mL) of 4-methylsulfide phenol (10.0 g, 71.4 mmol)
and triethylamine (7.96 g, 78.6 mmol) was added acryloyl chloride
(7.12 g, 78.6 mmol) in CH2Cl2 (20 mL) at 0 °C for 30 min. After the
reaction mixture was stirred at room temperature overnight, the
mixture was filtered. The filtrate was collected and washed with
1 N HCl(aq), 1 N Na2CO3(aq), and water. The organic layer was
dried with MgSO4. The solution was evaporated to give 4-acryl-
oxyphenyl methylsulfide as pale brown liquid. Yield: 11.3 g (58.2
mmol, 81.5%) 1H NMR (CDCl3, 300 MHz) δ (ppm): 7.26 (2H, d, J =
8.9 Hz), 7.05 (2H, d, J = 8.9 Hz), 6.58 (1H, dd, J = 17.3, 1.3 Hz), 6.29
(1H, dd, J = 17.3, 10.4 Hz), 5.98 (1H, dd, J = 10.4, 1.3 Hz), 2.45
(3H, s). 13C NMR (CDCl3, 75 MHz) δ (ppm): 164.50, 148.27,
135.72, 132.64, 127.96, 127.81, 121.97, 16.44.
Synthesis of 4-Acetoxyphenyldimethylsulfonium Triflate (DMS-Ac).
To a CH2Cl2/CH3CN mixture solution (10/1 mL) containing 4-acet-
oxyphenyl methylsulfide (2.0 g, 11.0 mmol) methyl triflate (2.0 g,
12.1 mmol) was slowly added at 40 °C and allowed to react for 13.5 h.
Afterward, the reaction mixture was cooled down to room temper-
ature, and the mixture was poured into large portion of diethyl ether.
The precipitate was collected and dissolved in acetone. The acetone
solution was poured into large portion of diethyl ether to yield
4-acetoxyphenyl dimethylsulfonium triflate as white powder. Yield: 3.3 g
1
(9.5 mmol, 86.4%). H NMR (DMSO-d6, 300 MHz) δ (ppm): 8.12
(2H, d, J = 8.8 Hz), 7.51 (2H, d, J = 8.8 Hz), 3.26 (6H, s), 2.31
(3H, s). 13C NMR (DMSO-d6, 75 MHz) δ (ppm): 168.91, 154.45,
131.79, 124.20, 123.71, 120.79 (q, J = 322.2 Hz), 28.48, 20.94. 19F
NMR (DMSO-d6) δ (ppm): −78.1 (3F, s). FT-IR (ATR mode):
1763 cm−1 (CO reactive ester band). Anal. Calcd for C11H13F3O5S2
(346.34): C, 38.15; H, 3.78. Found: C, 37.86; H, 3.64.
Determination of Theoretical Degree of Polymerization for
RAFT Polymerization. In a RAFT polymerization, a theoretical
degree of polymerization was calculated as follows:
[monomer]
0
DP
theoretical
=
× (monomer conv)
[CTA]
0
The monomer conversion was directly determined from the 1H NMR
measurements of the polymerization mixtures.
SEC Measurements of the Polymers. Based on the fact that the
obtained polymers are of highly ionic nature, the SEC measurement
of the polymer was very difficult. Hence, the polymer was dissolved
in DMSO and kept at 120 °C overnight in order to selectively
decompose sulfonium ion structure in the polymer. The polymer
solution was poured into large amount of MeOH. The obtained
polymer was then used for SEC measurements in THF.
Synthesis of 4-Acryloxyphenyldimethylsulfonium Triflate (SR-AEM).
To a CH2Cl2/CH3CN mixture solution (40/4 mL) of 4-methylsulfide
phenoxy acrylate (8.0 g, 41.2 mmol) methyl triflate (7.4 g, 45.2 mmol)
was slowly added at 40 °C and allowed to react for 16 h. Afterward,
the reaction mixture was cooled down to room temperature, and the
mixture was poured into large portion of diethyl ether. The precipitate
was collected and dissolved in hot THF. The THF solution was
poured into large portion of diethyl ether to yield 4-acryloxyphenyldi-
methylsulfonium triflate as pale yellow solid. Yield: 14.6 g (40.7 mmol,
ASSOCIATED CONTENT
* Supporting Information
■
S
Figure S-1. This material is available free of charge via the
1
98.8%). H NMR (DMSO-d6, 300 MHz) δ (ppm): 8.14 (2H, d, J =
8.9 Hz), 7.59 (2H, d, J = 8.9 Hz), 6.58 (1H, dd, J = 17.2, 1.5 Hz), 6.44
(1H, dd, J = 17.2, 10.1 Hz), 6.21 (1H, dd, J = 10.1, 1.5 Hz), 3.27
(3H, s). 13C NMR (DMSO-d6, 75 MHz) δ (ppm): 163.75, 154.18,
134.68, 131.85, 127.26, 124.14, 123.98, 120.79 (q, J = 322.2 Hz), 28.47.
19F NMR (DMSO-d6) δ (ppm): −78.1 (3F, s). FT-IR (ATR-mode):
1739 cm−1 (CO reactive ester band) Anal. Calcd for C12H13F3O5S2
(358.35): C, 40.22; H, 3.66. Found: C, 40.09; H, 3.57.
General Procedure for RAFT Polymerization of SR-AEM. RAFT
polymerization of SR-AEM was carried out as follows: An acetonitrile
solution (1.5 mL) containing SR-AEM (500 mg, 1.4 mmol),
pentafluorophenyl-(4-phenylthiocarbonylthio-4-cyanovalerate) (12.5 mg,
0.028 mmol), and AIBN (2.3 mg, 0.014 mmol) was degassed with Ar at
room temperature for 15 min. After degassing, the reaction mixture was
stirred at 90 °C for 2 h. The reaction mixture was then cooled down and
exposed to air to quench the polymerization. A portion of the reaction
mixture was collected for the purpose to determine the monomer
conversion, while the rest of the reaction mixture was diluted with
acetonitrile. The polymer was purified by reprecipitation (acetonitrile/
THF) to produce pale red solid. Yield: 368 mg (73.6%).
AUTHOR INFORMATION
Corresponding Author
*Tel +49 (0) 40 42838 6009; Fax +49 (0) 40 42838 6008;
■
ACKNOWLEDGMENTS
■
Ryohei Kakuchi gratefully acknowledges the support by a
Grant-in-Aid for the Japan Society for the Promotion of Science
(JSPS) Fellows.
REFERENCES
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Synthesis of Model Compounds. Synthesis of 4-Acetoxy-
phenyl Methylsulfide (MS-Ac). To a CH2Cl2 solution (15 mL) of
4-methylsulfide phenol (5.0 g, 35.7 mmol) and triethylamine (3.98 g,
39.3 mmol) acetyl chloride (7.12 g, 39.3 mmol) in CH2Cl2 (10 mL)
was added at 0 °C for 30 min. After the reaction mixture was stirred at
room temperature overnight, the mixture was filtered. The filtrate was
collected and washed with 1 N HCl(aq), 1 N Na2CO3(aq), and water.
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dx.doi.org/10.1021/ma202175z | Macromolecules 2012, 45, 1331−1338