Supplemental Information

Chain Mixing Behavior at Interface between Polystyrene Brushes and Polystyrene Matrices

Hiroshi Arita,Motoyasu Kobayashi,Norifumi L. Yamada, Hiroshi Jinnai,

and Atsushi Takahara*

1. Materials

A copper(I) bromide (CuBr, Wako Pure Chemical Industries, Ltd., Osaka, Japan, 98%) was washed successively with acetic acid and ethanol and and dried under vacuum. An ethyl 2-bromoisobutyrate (EB, Tokyo Chemical Industry Co., Ltd., Tokyo, Japan, 99%) was distilled from calcium hydride before use. Dichloromethane (Kishida Chemical Co., Fukuoka, Japan) and dry toluene (Kishida Chemical Co., Fukuoka, Japan) were purified by a solvent purification apparatus (Sovent Dipensing System, Nikko Hansen Co., Osaka, Japan) to remove water. Tris-(2-(dimethyl)aminoethyl)amine (Me6TREN)[1] was synthesized using previously reported procedures.Pentamethyldiethylenetriamine (PMDETA, Aldrich) was used as received. A styrene monomer (Wako Pure Chemical Industries, Ltd., Osaka, Japan, 99.0 %) was washed with NaOH aq. to remove stabilizer and dried over magnesium sulfate and then purified by distillation under reduced pressure in presence of calcium hydride. dPS (Mn=37000, Mw/Mn=1.02) was purchased from polymer source inc. Water for floating the self-standing dPS film was purified by the Simpli Lab system (Millipore Co., Ltd.).

Scheme S1. Synthesis of BMS

2. Synthesis of 11-(2'-bromo-2'-methyl)propionyloxyundecenyltrimethoxysilane (BMS) (See Scheme S1)

To a stirred solution of 10-undecen-1-ol (Aldrich, 49.6 mmol) and triethylamine (Wako Chemical, 71.9 mmol) in 40 mL of dry dichloromethane under nitrogen, 2-bromoisobutyloyl bromide (Aldrich, 50.0 mmol) in 10 mL of dry dichloromethane was added dropwise at 0 C. The reaction mixture was stirred at r.t for 7 h. The triethylamine hydrochloride salt was filtered off. The resulting solution was washed twice with a 1 M HCl aqueous solution and successively with water, and then dried over anhydrous magnesium sulfate. After removal of the drying agent and evaporation of the solvent, the residue was purified by distillation under vacuum to afford 12.25 g of 10-undecenyl 2'-bromoisobutylate (38.7 mmol, 78%) as a colorless liquid. bp. 92 C/ 0.1 mmHg. 1H NMR (CDCl3)  = 1.35 (s, 6H), 1.40 (m, 4H), 1.70 (p, 2H), 1.98 (s, 6H), 2.05 (m, 2H), 4.20 (t, 2H), 4.96 (dd, 2H), 5.86 (m, 1H). 13C NMR (CDCl3)  = 25.8 (CH2), 28.3 (CH2), 28.9 (CH2), 29.0 (CH2), 29.1 (CH2),29.4 (CH2), 30.8 (CH2), 33.8 (CH2), 56.0 (αC), 66.1 (OCH2), 114.1 (CH2=), 139.2 (CH=), 171.2 (C=O).

A mixture of 10'-undecenyl 2-bromoisobutylate (10.1 mmol) and trimethoxysilane (Aldrich, 20.5 mmol) was stirredin the two-neck flask under nitrogen gas atmosphere at 15 C. A 0.1 mL of Karstedt catalyst[2][3] solution for hydrosilylation consisting of platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisoloxane complex solution in xylenes (Aldrich) was added to the mixture every 2 h. The reaction mixture was stirred for overnight at 15 C. Excess amount of trimethoxysilane was remove in vacuo to give a pale yellow solution. The residue was diluted with hexane and was passed through the flash column filled with sodium sulfate and silica gel to remove the catalyst. Distillation of the resulting solution under vacuum gave a 0.73 g (1.61 mmol, 16%) of BMS as a colorless viscose liquid. bp. 160C/ 0.1 mmHg. 1H NMR (CDCl3)  = 0.68 (t, 2H, SiCH2), 1.35 (br, 12H), 1.40 (m, 4H), 1.71 (p, 2H), 1.95 (s, 6H, αCH3), 3.59 (s, 9H, OCH3), 4.20 (t, 2H, OCH2). 13C NMR (CDCl3) = 9.13 (SiCH2), 22.6 (αCH3),25.8 (CH2), 28.3 (CH2), 29.11 (CH2),29.15 (CH2),29.2 (CH2), 29.50 (CH2), 29.55(CH2), 30.8 (CH2), 33.1 (CH2), 50.5 (OCH3), 56.0 (αC), 66.2 (OCH2), 171.8 (C=O).

Scheme S2. Synthesis of HMS

3. Synthesis of 11-(2'-methyl)propionyloxyundecenyltrimethoxysilane (HMS) (See Scheme S2)

To a stirred solution of 10-undecen-1-ol (82.3 mmol) and triethylamine (89.1 mmol) in 40 mL of dry dichloromethane under nitrogen, 2-metylpropionyl chloride (Aldrich, 86.3 mmol) in 10 mL of dry dichloromethane was added dropwise at 0 C. The reaction mixture was stirred at r.t for overnight. The ammonium salt was filtered off. The resulting solution was washed with with a sat. aq. NaHCO3 solution, a 1 M HCl aqueous solution and successively with water, and then dried over anhydrous magnesium sulfate. After removal of the drying agent and evaporation of the solvent, the residue was purified by distillation under vacuum to afford 9.40 g of 10-undecenyl 2'-methylpropionate (39.1 mmol, 48%) as a colorless liquid. bp. 101C/ 0.15 mmHg. 1H NMR (CDCl3)  = 1.35 (s, 6H), 1.40 (m, 4H), 1.70 (p, 2H), 1.98 (s, 6H), 2.05 (m, 2H), 4.20 (t, 2H), 4.96 (dd, 2H), 5.86 (m, 1H).

A mixture of 10-undecenyl 2'-methylpropionate (16.4 mmol) and trimethoxysilane (34.6 mmol) was stirredin the two-neck flask under nitrogen gas atmosphere at 15 C. A 0.1 mL of Karstedt catalyst solution was added to the mixture every 2 h. The reaction mixture was stirred for overnight at 15 C. Excess amount of trimethoxysilane was remove in vacuo to give a pale yellow solution. The residue was diluted with hexane and was passed through the flash column filled with sodium sulfate and silica gel to remove the catalyst. Distillation of the resulting solution under vacuum gave a 3.71 g (8.41 mmol, 16%) of HMS as a colorless liquid. bp. 156C/ 0.1 mmHg. 1H NMR (CDCl3)  = 0.68 (t, 2H, SiCH2), 1.18 (2s, 6H, αCH3), 1.28 (br, 12H), 1.33 (m, 2H), 1.40 (m, 2H), 1.62 (m, 2H), 2.55 (m, 1H, αCH), 3.59 (s, 6H, αCH3), 4.07 (t, 2H, OCH2). 13C NMR (CDCl3)  = 9.02 (SiCH2), 18.8 (αCH3),22.4 (CH2), 25.8 (CH2), 28.5 (CH2), 29.11 (CH2),29.14 (CH2), 29.34 (CH2), 29.37 (CH2), 29.42 (CH2), 32.9 (CH2), 33.9 (CH), 50.2 (OCH3), 64.2 (OCH2), 176.9 (C=O).

4. Silicon wafers immobilized with surface initiator

Silicon wafers (40×15× t0.5 mm3) were washed with piranha solution at 373 K for 1 h and then exposed to vacuum-ultraviolet rays (VUV, λ = 172 nm) for 10 min under reduced pressure (30 Pa). (Caution: piranha solution consisting of concentrated sulfuric acid and hydrogen peroxide is danger solution, which should be handled with care.) The hydrophilic silicon wafers were immersed in the 0.5% BMS/ dry toluene solution at r.t. under nitrogen gas in a grove box for 4 h. The wafers were rinsed with ethanol (HPLC grade, Wako Chemical Co.) and annealed at 383 K for 3 h to give BMS-immobilized silicon wafer. Graft density of surface initiation site on the silicon wafer was tuned by the mixing ratio of BMS/ HMS (2/8 – 1/50) in dry toluene solution. Silicon wafers immersed in a mixture toluene solution of BMS and HMS gave the hPS brush with low graft density by the surface-initiated ATRP of styrene.

5. Preparation of hPS brushes

Several sheets of the BMS-immobilized and BMS/HMS mixture-immobilized silicon wafers and10 mL of styrene (86.1 mmol) were placed in a well-dried glass tube with a stopcock, and degassed three times by the freeze-thaw process.CuBr (0.086mmol),ME6TREN (0.177 mmol)and free initiator EB (0.087 mmol) diluted with isopropanol were introduced into another glass tube. The copper catalyst solution was degassed by repeated freeze-thaw cycles and then injected into the styrene solution. The resulting reaction mixture was again degassed by repeated freeze-thaw cycles to remove the oxygen and then was stirred in an oil bath at 348 K for 20 h under argon to simultaneously generate a PS brush from the substrate and free (unbound) PS fromEB. The reaction mixture was cooled down to 273 K and the stopcock was opened in air to quench the reaction. The reaction mixture was poured into methanol toprecipitate the free polymer in a 36% yield. The resulting hPS had a predictable molecular weight (Mn = 38700) and relatively narrow MWD (Mw/Mn = 1.12). The silicon wafers were washed with toluene using a Soxhlet apparatus for 6 h to remove the free polymer adsorbed on the surface, and were dried under reduced pressure.

The hPS brush with broad MWD was prepared by the similar surface-initiated ATRP procedure using CuBr and PMDETA in anisole at 383 K for 17 h. Amount of chemical reagents were as follows; 7.0 mL of styrene (60.5 mmol), 3.0 mL of anisole, 0.20 mmol of CuBr, 0.40 mmol of PMEDTA, 0.10 mmol of EB. The molecular weight and MWD of the free hPS (79% yield) were Mn = 51900 and Mw/Mn = 2.20, respectively.

6. Characterization

Size exclusionchromatography was performed at 40ºC on a Tosoh HLC-8220 GPC system(Tokyo, Japan) connected to three PS gel columns of TSK gel SuperH6000, 4000 and 2500 (Tosoh, Yamaguchi, Japan), and equipped with refractive index and an ultraviolet–visible detector. THF was used as theeluent at a flow rate of 0.6mL·min-1. Polystyrene standards (Mn=1060–1,090,000; Mw/Mn=1.02–1.08) were used for calibration to estimate thenumber-average molecular weight (Mn) and molecular weight dispersity index (Mw/Mn) of the polymers. The SEC profile of hPS-3 was shown in Figure S1.

Figure S1. SEC curved of polystyrene (hPS-3)

7. Fitting for NR profile of dPS/hPS3 bilayer filmsby parabolic function

Figure S2. (a) Neutron reflectivity profiles for dPS/hPS3 bilayer films annealed at 398 K for 120 min (plot) and the corresponding fitting curves (lines), and (b) scattering length density profiles for dPS/hPS3 interface (1) before annealing, (2)(3) after annealing. Blue line (2) and red line (3) represent the best fit SLD for NR and SLD profile based on parabolic function and Gaussian tail.

Figure S3. Volume fraction profile of hPS-3 brush (1) before annealing and after annealing at 398 K for 120 min calculated by (2) best fit SLD profile and (3) based on Parabolic function.

References

1

[1]J. Queffelec,; S. G. Gaynor,; K. Matyjaszewski, Macromolecules,2000, 33, 8629.

[2] Lewis, L. N.; Stein, J.; Smith, K. A.; Messmer, R. P.; Legrand, D. G.; Scott, R. A. Recent Mechanism Studies on Hydrosilylation. In Progress in Organosilicon Chemistry; Gordon and Breach Publishers: Langhorne, PA, 1993; pp 267-285

[3] Ojima, I. The Hydrosilylation Reaction. In The Chemistry of Organic Silicon Compounds; Patai, S., Rappoport, Z., Eds.; John Wiley & Sons: New York, 1989.