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Synthesis of Well-defined Amphiphilic Block Copolymers by. Organotellurium-Mediated Living Radical Polymerization (TERP). Santosh Kumar,Mohammad ...
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Supporting Information for Macromol. Rapid Commun., DOI: 2011, 32, 1576.

Synthesis of Well-defined Amphiphilic Block Copolymers by Organotellurium-Mediated Living Radical Polymerization (TERP) Santosh Kumar, Mohammad Changez, C. N. Murthy, Shigeru Yamago and Jae-Suk Lee*

Santosh Kumar, Mohammad Changez, Jae-Suk Lee Department of Nanobio Materials and Electronics and School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju, 500-712, Korea Tel: +82629702306; Fax: +82629702304; * Email: [email protected] Santosh Kumar, C. N. Murthy Applied Chemistry Department, Faculty of Technology & Engineering, The M. S. University of Baroda, Vadodara, Gujarat, 390-002, India Shigeru Yamago Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan

Experimental Methods Materials Ethyl-2-bromoisobutyrate (Aldrich, 98%), tellurium powder (Aldrich, -200 mesh, 99.8% metal basis), methyllithium (Aldrich, 1.6 M soln. in diethyl ether) were used as recieved. The monomers styrene (St) (Aldrich, 99%) and 2VP (Aldrich, 97%) were passed through activated alumina, dried for 24 h over calcium hydride and finally distilled under reduced pressure.

2,2’-Azobisisobutyronitrile (AIBN, Acros, 98% ) was recrystallized from methanol. Tetrahydrofuran (THF, Aldrich, 99.9%) and 1-methyl-2-pyrrolidinone (NMP, Aldrich, 99.5%) were used after drying over calcium hydride and then distilled under reduced pressure. Titanium tetraisopropoxide (TTIP) (Aldrich, 97%) was used as received. Silicon wafer were purchased from Prolog Semicor, Ltd., Ukraine. The silicon wafers were treated with piranha solution (70/30 v/v of concentrated H2SO4 and 30 % H2O2; caution! Piranha solution reacts violently with organic compounds and should not be stored in a closed container). All Other reagents were commercially available and were used without further treatment. Methods To determine number average molecular weight (Mn) and molecular weight distribution, (Mw/Mn) size exclusion chromatography, (SEC) was performed using a Waters M 77251, and M 510 with four columns (HR 0.5, HR 1, HR 3, and HR 4, Waters Styragel columns run in series). The pore sizes of the columns were 50, 100, 103, and 104 Å with a refractive index detector and a flow rate of 1 mL/min. Tetrahydrofuran (THF) containing triethylamine (2%, (C2H5)3N) was used as the elution solvent at 40 °C, and the instrument was calibrated with styrene standards of 0.889 k, 4 k, 10.4 k, 30 k, 44 k and 104 k (American Polymer Standards Corp.). Nuclear magnetic resonance (1H NMR) spectra were recorded using a JEOL JNMLA300WB. All spectra were taken in CDCl3 and the chemical shifts were referenced to tetramethysilane (TMS) at 0 ppm. The glass transition temperatures (Tg) of the polymer were measured in the range of 30-200 °C at a heating rate of 10 °C/min and was determined from the middle of the change in heat capacity using differential scanning calorimeter (DSC-TA Instrument Q-20). A field-emission scanning electron microscope (FE-SEM, HITACH S-4700) was used at 10 kV with specimens coated on a silicon wafer. An energy dispersive X-ray microanalyzer (EMAX, HORIBA-7200H) attached to an FE-SEM was used for elemental analysis. A Fieldemission transmission electron microscope (FE-TEM, JEOL JEM-2100F) operating at 200 kV

was used to observe the size and morphology. The TEM sample was prepared by dropping a polymer solution onto a carbon coated copper grid and drying at 150 oC. Before measurement, P2VP-b-PS, the P2VP domain of the block copolymer was stained with I2 vapor for 10 h. Synthesis of TERP Promoter Ethyl-2-methyl-2-methyltellanyl-propionate (MTEE)[1] To a suspension of tellurium metal (6.38 g, 50 mmol) in 50 mL of THF, methyllithium (34 mL, 1.6 M solution in diethyl ether, 55 mmol) was slowly added over 20 min at room temperature. The resulting mixture was stirred for 10 min until tellurium metal completely disappeared. To this solution ethyl 2-bromo-isobutyrate (10.70 g, 55 mmol) was added and the resulting solution was stirred for 2 h. The solvent was removed under reduced pressure followed by distillation under reduced pressure to give MTEE as red oil in 47 % yield (6.53 g, 25.3 mmol). MTEE, 1H NMR (300 MHz, CDCl3) 1.27 (t, J = 6.9 Hz, 3H), 1.74 (s, 6H), 2.15 (s, 3H, TeCH3), 4.16 (q, J = 7.2 Hz, 2H). Homopolymerization and Block copolymerizations Homopolymerization of Styrene (1) Styrene (4.0 g, 38.4 mmol) and AIBN (0.15 g, 0.96 mmol) were dissolved in 5 ml of NMP in a 50 ml two-necked round-bottom flask equipped with a magnetic stirring bar and rubber septum. Following, the solution was deoxygenated by purging with argon for 30 min. MTEE (0.24 g, 0.96 mmol) was then added through a syringe, which was previously flushed with argon. The polymerization was conducted at 65 °C for 12 h under argon atmosphere. At different time intervals, a small portion of the polymerization mixture was sampled using a syringe and subjected to measurement for molecular weight by SEC and conversion by gravimetry. Homopolymerization of 2VP (2) 2VP (9.75 g, 92.7 mmol) and AIBN (0.15 g, 0.92 mmol) were dissolved in 9 ml of NMP in 100 ml two-necked round-bottom flask equipped with a magnetic stirring bar and rubber septum. Following, the solution was deoxygenated by purging with argon for 30 min. MTEE

(0.23 g, 0.92 mmol) was then added with a syringe that had been previously flushed with argon. The polymerization was conducted at 65 °C for 15 h under an argon atmosphere. At different time intervals, a small portion of the polymerization mixture was sampled using a syringe and subjected to measurement for molecular weight by SEC and conversion by gravimetry. Block copolymerization of styrene with 2VP (3) A representative example (3a) of the preparation of the diblock copolymers of styrene and 2VP is as follows: styrene (3.95 g, 38.0 mmol) and AIBN (0.31 g, 1.90 mmol) were dissolved in 4 ml of NMP in a 100 ml two-necked round-bottom flask equipped with a magnetic stirring bar and rubber septum. Then, the solution was deoxygenated by purging with argon for 30 min. MTEE (0.48 g, 1.90 mmol) was added to this flask through a syringe that had been previously flushed with argon. The polymerization was conducted at 65 °C for 15 h under argon atmosphere. The reaction mixture containing the styrene homopolymer was sampled and subjected to measurement for molecular weight by SEC and conversion by gravimetry. SEC and gravimetric analyses indicated that the Mn of the first block was 2246 with a Mw/Mn of 1.12, as shown in Table 2, and a conversion of >95%, respectively. Next, the second monomer, 2VP (4.0 g, 38.0 mmol), and AIBN (0.13 g, 0.76 mmol) were introduced via syringe to the flask after deoxygenating the solution with argon for 30 min. The second stage polymerization at 65 °C was allowed to continue for 17 h. After completion of the polymerization, Mn and Mw/Mn were measured by SEC and gravimetric conversion, respectively. The polymers were purified by reprecipitation from tetrahydrofuran into a large excess of hexane. During the synthesis of (3b), a similar polymerization was performed, and Mn of the first block was 2100 with a Mw/Mn of 1.10, as shown in Table 2. 2VP (4.0 g, 38.0 mmol) and AIBN (0.31 g, 1.90 mmol) were added at the second stage of the polymerization. Block copolymerization of 2VP with Styrene (4)

A representative example (4) of the preparation of the diblock copolymer of 2VP and styrene is as follows: 2VP (4.0 g, 38.0 mmol) and AIBN (0.34 g, 2.10 mmol) were dissolved in 4 ml of NMP in a 100 ml two-necked round-bottom flask equipped with a magnetic stirring bar and rubber septum. Then, the solution was deoxygenated by purging with argon for 30 min. MTEE (0.54 g, 2.10 mmol) was added to this flask through a syringe that had been previously flushed with argon. The polymerization was conducted at 65 °C for 17 h under argon atmosphere. The reaction mixture containing 2VP homopolymer was sampled and subjected to measurement for molecular weight by SEC and conversion by gravimetry. SEC and gravimetric analyses indicated that the Mn of the first block was 1862 with a Mw/Mn of 1.13, as shown in Table 2, and a conversion of >99 %, respectively. Then, the second monomer, styrene (3.90 g, 38.0 mmol), and AIBN (0.52 g, 3.16 mmol) were introduced via syringe to the flask after deoxygenating the solution with argon for 30 min. The second stage polymerization at 65 °C was allowed to continue for 15 h. After completion of the polymerization, Mn and Mw/Mn were measured by SEC and gravimetric conversion, respectively. The polymers were purified by reprecipitation from tetrahydrofuran into a large excess of hexane. P2VP-b-PS (4) Block Copolymer Micelles and TiO2 Nanostructures P2VP-b-PS (Mn = 3200 g/mol, Mw/Mn = 1.15) block copolymer solutions (10 wt %) were dissolved in toluene under vigorous stirring and sonicated for 3 days. Next, the sol-gel solution was prepared by adding isopropyl alcohol (5 mL), TTIP (0.125 mmol), and HCl (0.125 mmol). Subsequently, toluene (5 mL) was slowly dropped into the homogeneous mixture of the sol-gel and stirred for 1 h. Afterward, the desired amount of sol-gel (30, 40, 50, or 60 vol % relative to the block copolymer amount) was added to the block copolymer solution and stirred for 30 min. Finally, the mixed solutions were filtered using a 0.45 µm PTFE filter. The clear yellow solution could be stored at room temperature for several weeks without apparent changes. Hybrid inorganic/organic films were produced by spin coating onto

Si (100) wafers at 2000 rpm for 30 s using a Model-YS-100D (Won Corporation, Korea) spin-coater. In view of the similar morphologies of all of the synthesized nanocomposites for each sol-gel content used, the data are described only for the 60 vol. % sol-gel/P2VP-b-PS nanocomposite. As-deposited films were annealed at 150 oC for 6 h and then oxygen plasma etching (Miniplasma. Co., Korea) at 120 Watts, 10-2 Torr for 20 min

[2]

was employed to remove the

organic template from the P2VP-b-PS/titania nanocomposite leaving behind the pure titania domains.

Figure S1. The second heating scan for the DSC profile of P2VP-b-PS (4), diblock copolymer.

References: [1] S. Yamago, K. Iida, J. Yoshida, J. Am. Chem. Soc. 2002, 124, 13666. [2] J. P. Spatz, S. Mössmer, C. Hartmann, M. Moller, Langmuir 2000, 16, 407.