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.).
O
Br
Br
9
O
OH
Et3N
9
HSi(OMe)3
Br
O
Pt cat.
O
(MeO)3Si
O
11
Br
BMS
Scheme S1. Synthesis of BMS
2. Synthesis of 11-(2'-bromo-2'-methyl)propionyloxyundecenyltrimethoxysilane (BMS) (See
Scheme S1)
1
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.
1
H 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).
13
C 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 stirred in 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.
1
H 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).
13
C 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).
O
Br
9
O
OH
Et3N
9
O
HSi(OMe)3
Pt cat.
O
(MeO)3Si
O
11
HMS
2
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.
1
H 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 stirred in 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.
1
H 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).
C NMR (CDCl3)  = 9.02 (SiCH2), 18.8 (αCH3), 22.4
13
(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
3
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 and 10 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 (0.086 mmol),
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 from EB. 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 to precipitate 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.
4
6. Characterization
Size exclusion chromatography was performed at 40 ºC on a Tosoh HLC-8220 GPC system
(Tokyo, Japan) connected to three PS gel columns of TSK gel SuperH 6000, 4000 and 2500
(Tosoh, Yamaguchi, Japan), and equipped with refractive index and an ultraviolet–visible
detector. THF was used as the eluent at a flow rate of 0.6 mL·min-1. Polystyrene standards
(Mn=1060–1,090,000; Mw/Mn=1.02–1.08) were used for calibration to estimate the
number-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.
hPS-3
Mn = 51900
Mw/Mn=2.02
10
7
10
6
10
5
10
4
10
Figure S1. SEC curved of polystyrene (hPS-3)
5
3
7. Fitting for NR profile of dPS/hPS3 bilayer films by parabolic function
(a) 100
Open circle: NR data
Blue line: Best fit curve
Red line: Fit curve based on
Parabolic function
Reflectivity
10-1
10-2
10-3
10-4
0.4 0.5
10-5
0.2
Distance from Si substrate, nm
(b)
0.3 0.4 0.5
q, nm-1
1
2
Air
150
d-PS film
100
2
3
1
50
00
h-PS brush
1
2
3
4
5
SLD, 10-4 nm-2
6
7
1: SLD before annealing
2: Best fit SLD after annealing
3: SLD based on 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.
6
Volume fraction of hPS
1.0
0.8
0.6
(z) of hPS-3
0.4
0.2
0
1
-40
3
2
-20
0
20
40
Z, nm
1: Volume fraction before annealing
2: Volume fraction based on best fit SLD
3: Volume fraction based on Parabolic function
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
J. Queffelec,; S. G. Gaynor,; K. Matyjaszewski, Macromolecules, 2000, 33, 8629.
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.
2
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