Solvent-Selective Reactions of Alkyl Iodide with Sodium Azide for Radical Generation and Azide

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1 Supporting Information Solvent-Selective Reactions of Alkyl Iodide with Sodium Azide for Radical Generation and Azide Substitution and Their Application to One-Pot Synthesis of Chain-End Functionalized Polymers Chen-Gang Wang, Atsushi Goto* Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 1. Experimental Section Materials. Methyl methacrylate (MMA) ( 99.8%, Tokyo Chemical Industry (TCI), Japan), butyl acrylate (BA) ( 99%, TCI), benzyl methacrylate (BzMA) ( 98%, TCI), butyl methacrylate (BMA) ( 99%, TCI), lauryl methacrylate (LMA) ( 97%, TCI), and poly(ethylene glycol) methacrylate (PEGMA) (average molecular weight = 300) (98%, Aldrich, USA) were purified through an alumina column. 2-Iodo-2-methylpropionitrile (CP I) ( 95%, TCI), ethyl 2-iodo-2-methylpropionate (EMA I) ( 94%, TCI), ethyl α-iodophenylacetate (EPh I) ( 98%, TCI), iodine (I 2 ) ( 98%, TCI), 18-crown-6- ether ( 98%, TCI), tetrabutylammonium iodide (BNI) (>98%, TCI), 2,2,6,6-tetramethylpiperidine-1- oxyl (TEMPO) (>98%, Aldrich), ammonia solution (28% in water, TCI), polyethylene glycol monomethyl ether (PEG-OH, average molecular weight = 1000) (TCI), 1H,1H,2H,2H-heptadecafluoro- 1-decanol (>98 %, TCI), propargyl bromide (>97%, TCI), copper(i) bromide ( 98%, Aldrich), N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) (>99%, TCI), isopropyl alcohol (>99.5%, TCI), sodium thiocyanate (NaSCN) ( 99.99%, Aldrich), tetrabutylammonium thiocyanate (BNSCN) (98%, Aldrich), sodium azide (NaN 3 ) ( 99.5%, Aldrich), sodium cyanate (NaOCN) (96%, Aldrich), sodium hydride (60 % dispersion in mineral oil, Aldrich), toluene (>99.8%, TEDIA, USA), chloroform S1

2 (>99.2%, VWR Chemicals, USA), N,N-dimethylformamide (DMF) (>99.5%, Kanto Chemical, Japan), hexane (>99%, International Scientific, Singapore), acetone ( 99.5%, Fisher Scientific, USA), ethanol ( 99.5%, absolute, Fisher Scientific), methanol (>99%, International Scientific), and tetrahydrofuran (THF) (>99.5%, Kanto) were used as received. A silicon wafer (produced by Czochralski process, thickness: 525±25 μm) was purchased from Matsuzaki Seikakusho (Japan). 6-(2-Iodo-2- isobutyloxy)hexyltriethoxysilane (IHE) (>95%) was provided through the courtesy of Godo Shigen Co., Ltd. (Japan) and used as received. Measurement. The GPC analysis was performed on a Shodex GPC-101 liquid chromatograph (Tokyo, Japan) equipped with two Shodex KF-804L mixed gel columns ( mm; bead size = 7 m; pore size = Å). The eluent was tetrahydrofuran (THF) or dimethyl formamide (DMF) at a flow rate of 1.0 ml/min (THF) or 0.8 ml/min (DMF) (40 C). The DMF eluent included LiBr (10 mm). Sample detection and quantification were conducted using a Shodex differential refractometer RI-101 calibrated with known concentrations of polymer in solvent. The monomer conversion was determined from the peak area of GPC. The column system was calibrated with standard poly(methyl methacrylate)s (PMMAs). The NMR spectra were recorded on a Bruker (Germany) AV500 spectrometer (500 MHz) or Bruker BBFO400 spectrometer (400 MHz) at ambient temperature; Bruker AV500, 1 H: spectral width Hz, acquisition time sec, and pulse delay sec; Bruker BBFO400, 1 H and 19 F: spectral width Hz, acquisition time sec, and pulse delay sec. CDCl 3, DMSO d 6, toluene d 8, and acetone d 6 were used as the solvents for NMR analysis, and the chemical shift was calibrated using residual undeuterated solvents or tetramethylsilane (TMS) as the internal standard. The mass spectra were obtained with a Q-Tof Premier (Waters, USA) high-resolution liquid chromatography mass spectrometer (HRLC-MS). The IR spectra were recorded on a Bruker ALPHA FTIR spectrometer with KBr (spectroscopic grade, Alfa Aesar, USA) as a matrix. The cleaning of silicon wafer was carried out with a digital UV-ozone cleaner (PSD Pro Series, Novascan Technologies, Germany). The elemental (C, H, S, and N) analysis was carried out with a Euro EA-CHNSO Elemental S2

3 Analyser (HEKAtech, Germany) calibrated using (2,5-(bis(5-tert-butyl-2-benzo-oxazol-2-yl)thiophene (BBOT, Elemental Microanalysis, UK). The atomic force microscope (AFM) analysis was carried out on a scanning probe microscope (Probe Station AFM5000II, Hitachi High-Technologies, Japan) with a cantilever PRC-DF40P. The contact angle was measured with a DM-701 contact angle meter (Kyowa Interface Science, Japan). The X-ray photoelectron spectroscopy (XPS) analysis was carried out with a Phoibos 100 spectrometer and a monochromatic Mg X-ray radiation source (SPECS, Germany). Radical Trap Experiment. A mixture of toluene-d 8 (0.8 ml), CP I (20 mm), NaN 3 (20 mm), 18- crown-6-ether (20 mm), and TEMPO (40 mm) was heated in a Schlenk flask at 70 C for 3 h under argon atmosphere with magnetic stirring. After cooling to room temperature, the mixture was analyzed by 1 H NMR. Solvent-Selective Reaction of EMA I with NaN 3. A mixture of EMA I (20 mm), NaN 3 (20 mm), 18-crown-6-ether (20 mm), and a toluene-d 8 /acetone-d 6 mixed solvent (7/3 (w/w), 1.0 ml) was heated in a Schlenk flask 50 C for 1 h under argon atmosphere with magnetic stirring. After cooling to room temperature, the mixture was analyzed by 1 H NMR. Instead of the toluene-d 8 /acetone-d 6 mixture, DMSO-d 6 was also used as solvent. General Procedure for Polymerization. In a typical run, a mixture of monomer (2.0 g), an alkyl iodide initiator, NaN 3, and 18-crown-6-ether was heated in a Schlenk flask at C under argon atmosphere with magnetic stirring. After a prescribed time t, an aliquot (0.1 ml) of the solution was taken out by a syringe, quenched to room temperature, diluted by THF or DMF to a known concentration, and analyzed by GPC. One-Pot Synthesis of PMMA N 3. In a typical run, a mixture of MMA (1.5 g), CP I, NaN 3, 18- crown-6-ether, and toluene (0.5 g) was heated in a Schlenk flask at 70 C under argon atmosphere with magnetic stirring. After a prescribed time t, the mixture was quenched to room temperature, and DMF was added to the mixture (polymerization solution/dmf = 1/2 (w/w)). The solution was stirred at room temperature for 12 h. The solution was diluted with THF (5 ml), and the polymer was reprecipitated in S3

4 a water/methanol mixed solvent (v/v = 1/1, 150 ml) repeatedly. The polymer (PMMA N 3 ) was collected by filtration and dried under vacuum. Preparation of IHE-Immobilized Silicon Wafer. 1 A silicon wafer (1 cm 1 cm) was washed with acetone (with sonication for 30 min), chloroform (with sonication for 30 min), and isopropanol (with sonication for 30 min). After drying under nitrogen flow, the wafer was placed in the ozone cleaner and radiated for 30 min. The wafer was immersed in a mixture of IHE, aqueous ammonia solution, and ethanol (1/89/10 (w/w/w)) for one day. The wafer was washed with ethanol, sonicated in ethanol for 30 min, and dried under nitrogen flow to give an IHE immobilized silicon wafer. One-Pot Synthesis of N 3 -Chain-End PMMA brush. The IHE immobilized silicon wafer was immersed in a mixture of MMA (1.5 g), CP I, NaN 3, 18-crown-6-ether, and toluene (0.5 g) in a Schlenk flask and heated at 70 C under argon atmosphere with magnetic stirring for a prescribed time t. DMF was added to the mixture (polymerization solution/dmf = 1/2 (w/w)), and the solution was stirred at ambient temperature for 12 h. The wafer was washed with THF, sonicated in THF for 30 min twice, and dried under nitrogen flow. Copper-Catalyzed Azide-Alkyne Cycloaddition of PMMA N 3 with Alkynes. 2,3 In a typical run, a solution of PMMA N 3 (DP = 32) (100 mg, mmol), CuBr (6.40 mg, mmol) and PMDETA (15.27 mg, mmol) in THF (1.0 ml) in a Schlenk flask was purged with argon. In the second Schlenk flask, a solution of PEG alkyne (45.6 mg, mmol) in THF (1.0 ml) was purged with argon for 2 min. (The syntheses of PEG-alkyne and C 8 F 17 alkyne are described below.) The solution in the second flask was transferred to the first flask under argon atmosphere through a degassed syringe. After stirring for 24 h at room temperature under argon atmosphere, the solution was filtered to remove precipitated salts. The remaining solution included polymer. The polymer was reprecipitated in a methanol/water mixed solvent (2/1 (v/v)) twice to remove unreacted PEG alkyne. The polymer (PMMA PEG block copolymer) was collected by filtration and dried under vacuum. For C 8 F 17 alkyne, hexane was used for reprecipitation instead of the methanol/water mixture. S4

5 For the polymer brush, a silicon wafer fabricated with PMMA N 3 brush was immersed in a mixture of CuBr (5.81 mg, 0.04 mmol), PMDETA (13.9 mg, 0.08 mmol), and THF (1.0 ml) in a Schlenk flask and purged with argon. In a second Schlenk flask, a solution of an alkyne (PEG alkyne: 20.8 mg, 0.02 mmol or C 8 F 17 alkyne: 10.6 mg, 0.02 mmol) in THF (1 ml) was purged with argon. The solution in the second flask was transferred to the first flask under argon atmosphere through a degassed syringe. After stirring for 24 h at room temperature under argon atmosphere, the wafer was washed with THF with sonication in THF for 30 min twice. The wafer was further washed by methanol and dried under nitrogen flow. 2. Syntheses of CP N 3, EMA N 3, and Functional Alkynes. Synthesis of CP N 3. A mixture of CP I (0.7 g, 3.6 mmol), NaN 3 (0.26 g, 3.9 mmol), and DMF (3.6 ml) was stirred in a reaction tube at ambient temperature for 2 h. Deionized water (50 ml) was added to the mixture. The aqueous solution was extracted with ethyl acetate (3 30 ml). The organic layers were merged, washed with Na 2 S 2 O 3 (0.5 M) aqueous solution (50 ml), water (2 50 ml), and brine (3 50 ml), dried over Na 2 SO 4, filtered, and evaporated. CP N 3 was obtained as a yellow liquid. Yield: 53% (0.21 g, 1.9 mmol); 1 H NMR (400 MHz, 298 K, toluene d 8 ) δ 1.45 (s, 6H, (CH 3 ) 2 ) ppm; HRLC- MS (m/z): calcd for C 4 H 7 N + 4 [M+H] +, ; found, ). Synthesis of EMA N 3. A mixture of 2-bromo-2-methylpropionate (1.0 g, 5.1 mmol), NaN 3 (0.37 g, 5.6 mmol), and DMF (5.1 ml, 1.0 M) was stirred in a reaction tube at ambient temperature for 5 h. Deionized water (50 ml) was added to the mixture. The aqueous solution was extracted with ethyl acetate (3 30 ml). The organic layers were merged, washed with water (2 50 ml) and brine (3 50 ml), dried over Na 2 SO 4, filtered, and evaporated. EMA N 3 was obtained as a yellow liquid. Yield:78% (0.63 g, 4.0 mmol); 1 H NMR (400 MHz, 298 K, DMSO d 6 ) δ 4.17 (q, J = 7.12 Hz, 2H, CH 2 O ), 1.40 (s, 6H, (CH 3 ) 2 ), 1.22 (t, J = 7.12 Hz, CH 2 CH 3 ) ppm; 1 H NMR (400 MHz, 298 K, toluene-d 8 /acetone- S5

6 d 6 =7/3 (w/w)) δ 3.93 (q, J = 7.12 Hz, 2H, CH 2 O ), 1.22 (s, 6H, (CH 3 ) 2 ), 0.99 (t, J = 7.12 Hz, 3H, CH 2 CH 3 ) ppm. HRLC-MS (m/z): calcd for C 6 H 12 O 2 N 3 + [M+H] +, ; found, ). Synthesis of 3-(polyethylene glycol monomethyl ether)-prop-1-yne (PEG alkyne). The synthesis of PEG alkyne was referred to the literature. 2 To a solution of polyethylene glycol monomethyl ether (M n = 1000, 6.0 g, 6 mmol) in anhydrous THF (40 ml), NaH (0.6 g, 15 mmol, NaH was washed with hexane three times to remove mineral oil before use) was added. The reaction mixture was stirred at room temperature for 20 min. A solution of allylbromide (1.07 g, 9 mmol) in THF (10 ml) was added dropwise to the mixture, and the reaction mixture was stirred at room temperature for 6 h. The crude was filtered to remove the salts. The filtrate was evaporated and precipitated into cold hexane (100 ml). The precipitate was collect and dried under vacuum to give PEG alkyne as a soft solid. Yield: 88% (5.48 g, 5.3 mmol); 1 H NMR (400 MHz, 298 K, CDCl 3 ) (Figure S1) δ 4.20 (br, 2H, CCH 2 O ), 3.64 (br, OCH 2 CH 2 O ), 3.34 (s, 3H, OCH 3 ), 2.44 (br, 1H, HC C ) ppm; IR (KBr) (Figure S2) υ approximately 3300 (H C C), 2113(C C), 1102 (C O) cm 1. Figure S1. 1 H NMR spectrum (CDCl 3 ) of 3-(polyethylene glycol monomethyl ether)-prop-1-yne (PEG alkyne, M n = 1000). S6

7 Figure S2. IR spectrum of 3-(polyethylene glycol monomethyl ether)-prop-1-yne (PEG alkyne, M n = 1000). Synthesis of 3-((2-perfluorooctyl)ethoxy)prop-1-yne (C 8 F 17 alkyne). The synthesis of C 8 F 17 alkyne was referred to the literature. 4 1H,1H,2H,2H-Heptadecafluoro-1-decanol (5.0 g, 10.8 mmol) and sodium hydroxide (1.72 g, 43 mmol) were placed in a round-bottom flask with anhydrous THF (40 ml), and the mixture was stirred for 10 min at 0 C. A solution of allylbromide (1.92 g, 16.2 mmol) in THF (10 ml) was added dropwise to the reaction mixture. The reaction mixture was gradually warmed to room temperature and stirred for 24 h. To the reaction mixture, diethyl ether (20 ml) was added, and the solution was poured into deionized water (20 ml). The separated aqueous layer was extracted with diethyl ether (3 20 ml). The combined organic layers were merged and washed with 10wt% HCl aqueous solution, saturated NaHCO 3 aqueous solution, and brine. After drying over MgSO 4 and evaporating, the crude was purified by a silica gel column chromatography (eluent: hexane/etoet = 10/1). After drying under vacuum, C 8 F 17 -alkyne was obtained as a colorless oil. Yield: 65% (3.52 g, 7.01 mmol); 1 H NMR (400 MHz, 298 K, CDCl 3 ) (Figure S3) δ 4.18 (d, J = 2.32 Hz, 2H, CCH 2 O ), 3.82 (t, J = 6.80 Hz, 2H, OCH 2 CH 2 C 8 F 17 ), 2.46 (m, 2H, OCH 2 CH 2 C 8 F 17 ), 2.39 (t, J = 6.80 Hz, 1H, HC C ) ppm; 19 F NMR (400 MHz, 298 K, CDCl 3 ) (Figure S4) δ -81.8, , , , , S7

8 -124.6, ppm. IR (KBr) (Figure S5) υ 3317 (H C C), 2123(C C), 1218 (C F), 1142 (C O) cm 1. Figure S3. 1 H NMR spectrum (CDCl 3 ) of 3-((2-perfluorooctyl)ethoxy)prop-1-yne (C 8 F 17 alkyne). Figure S4. 19 F NMR spectrum (CDCl 3 ) of 3-((2-perfluorooctyl)ethoxy)prop-1-yne (C 8 F 17 alkyne). α,α,α-trifluorotoluene was uses as a reference standard with a calibration signal at ppm. S8

9 Figure S5. IR spectrum of 3-((2-perfluorooctyl)ethoxy)prop-1-yne (C 8 F 17 alkyne). 3. Polymerization of MMA with Lower Concentrations of NaN 3 catalyst. Figure S6. Plots of (a) ln([m] 0 /[M]) vs t and (b) M n and M w /M n vs conversion for the MMA/CP- I/NaN 3 /crown ether/i 2 systems (70 o C): [MMA] 0 = 8 M; [CP-I] 0 = 80 mm; [NaN 3 ] 0 = 40, 20, 10, and 5 mm; [crown ether] 0 = 40, 20, 10, and 5 mm; [I 2 ] 0 = 1 mm. The symbols are indicated in the figure. S9

10 Table S1. Bulk Polymerizations of MMA with CP I, NaN 3, Crown Ether, and I 2. Entry Target DP a R I Catalyst [MMA] 0 /[CP I] 0 /[NaN 3 ] 0 / [crown ether] 0 /[I 2 ] 0 (mm) T ( C) t (h) Conv (%) M n (M n,theo b ) CP I NaN /80/20/20/ (8800) CP I NaN /80/10/10/ (7500) CP I NaN /80/5/5/ (7200) 1.19 a Target degree of polymerization at 100% monomer conversion (calculated by [MMA] 0 /[CP I] 0 ). b Theoretical M n calculated with [MMA] 0, [CP I] 0, and monomer conversion. PDI 4. Polymerization of MMA for Higher Molecular Weights Figure S7. Plots of (a) ln([m] 0 /[M]) vs t and (b) M n and M w /M n vs conversion for the MMA/CP- I/NaN 3 /crown ether/i 2 systems (70 o C): [MMA] 0 = 8 M; [CP-I] 0 = 20 or 40 mm; [NaN 3 ] 0 = 40 mm; [crown ether] 0 = 40 mm; [I 2 ] 0 = 1 mm. The symbols are indicated in the figure. S10

11 Figure S8. GPC chromatograms for the MMA/CP-I/NaN 3 /crown ether/i 2 systems (70 o C): [MMA] 0 = 8 M; [CP-I] 0 = 40 mm; [NaN 3 ] 0 = 40 mm; [crown ether] 0 = 40 mm; [I 2 ] 0 = 1 mm (Table 1 (entry 6)). 5. Spectral Data Figure S9. IR spectra of (a) PMMA N 3 (DP = 51) and (b) PMMA N 3 (DP = 80). The reaction conditions for (a) and (b) are given in Table 3 (entries 2 and 3, respectively). S11

12 Figure S10. 1 H NMR spectrum (CDCl 3 ) of (a) PMMA N 3 (DP = 51), (b) PMMA N 3 (DP = 80), and (c) PMMA SCN (DP = 27). The reaction conditions for (a), (b), and (c) are given in Table 3 (entries 2, 3, and 4, respectively). Figure S11. 1 H NMR spectrum (CDCl 3 ) of (a) PMMA PEG (DP = 32), (b) PMMA PEG (DP = 51), and (c) PMMA PEG (DP = 80). The synthetic conditions for (a), (b), and (c) are given in Table 4 (entries 1, 2, and 3, respectively). S12

13 Figure S12. XPS survey spectra of (a) N 3, (b) PEG, and (c) C 8 F 17 -functionalized PMMA brushes on surface with 100% targeted surface coverage. (d) High resolution spectra of F 1s signal of C 8 F 17 - functionalized PMMA brush on surface (c). S13