Supporting Information
Photoinduced Grafting of Polystyrene onto Silica Particles by Ketene
Chemistry
Gorkem Yilmaz, Volkan Kumbaraci, Naciye Talinli, Pınar Tatar, A. Levent Demirel, Yusuf
Yagci*
Experimental Section
Materials
Styrene (S, 99 %, Aldrich) was passed through basic alumina column to remove the inhibitor.
N, N, N’, N’’, N’’-pentamethyldiethylenetriamine (PMDETA, 99 %, Aldrich) as a ligand, was
distilled before use. Ethyl-2-bromopropionate (99 %, Aldrich), CuBr (98 %, Acros), 2,6dihydroxybenzoic acid (97 %, Acros), N’,N’-dimethylpyridin-4-amine (DMAP, 99 %, Acros),
benzophenone (≥ 99 %, Aldrich), potassium carbonate anhydrous (99.9 %, Aldrich), sodium
sulfate anhydrous (≥ 99.0 %, Aldrich) silicagel 60 (Merck, 0.040-0.063 mm) and 3aminopropyl functionalized silica gel (Merck, 0.040-0.063 mm) were used as received. All
solvents were of HPLC or ACS grade. Solvents used for moisture sensitive operations were
distilled from drying reagents under a nitrogen atmosphere: Et2O from sodium benzophenone
ketyl, benzene and toluene from sodium, CH2Cl2 from CaH2.
Characterizations
1
H NMR measurements were recorded in CDCl3 with Si(CH3)4 as internal standard, using a
Bruker AC250 (250.133 MHz) instrument. FT-IR spectra were recorded on a Perkin-Elmer
FT-IR Spectrum One-B spectrometer. Fluorescence measurements were performed on a
Perkin Elmer LS55 spectrometer. Molecular weights were determined by gel permeation
chromatography (GPC) instrument, Viscotek GPCmax Autosampler system, consisting of a
pump, three ViscoGEL GPC columns (G2000HHR, G3000HHR and G4000HHR), and a
Viscotek differential refractive index (RI) detector with a THF flow rate of 1.0 mL min–1 at
30C. The RI detector was calibrated with PS standards having narrow molecular weight
distribution. Data were analyzed using Viscotek OmniSEC Omni–01 software.
Synthesis of 7-Hydroxy-2,2-diphenyl-4H-benzo[d][1,3]dioxin-4-one (Bd)
The precursor compound was synthesized according to the literature procedure.1 Thus, to an
ice-cold suspension of 2,4-dihydroxybenzoic acid (2.5 g, 16.23 mmol) in trifluoroacetic acid
(13 mL) were added trifluoroacetic anhydride (14 mL) and benzophenone (4.43 g, 24.37
mmol). The mixture was warmed slowly to room temperature and then stirred for 24 h. The
mixture was then concentrated on the rotary evaporator, poured into a saturated solution of
aqueous NaHCO3, and extracted with three portions of diethyl ether. Collected extracts were
washed with water and brine, dried over Na2SO4 and concentrated to leave yellow solids.
Chromatography over silica using EtOAc/Hex (30/70) as the eluent afforded 0.9 g (17 %) of
HDPD as yellow solid. mp; 63-65 °C. 1H NMR (250 MHz, CDCl3, δ): 10.43 (s, 1H, OH),
7.60-7.54 (dd, J=7.4, J=1.4, 4H, Ar), 7.35-7.31 (m, 6H, Ar), 7.71 (d, J=8.7, 1H, Ar), 6.63 (s,
1H, Ar), 6.52 (d, J=8.6, 1H, Ar). FT-IR (ATR): ν = 3230, 2975, 1687, 1612, 1594, 1491,
1447, 1240, 1121, 960, 750 cm-1. UV (CH2Cl2): λmax(ε) = 303 (8932), 263 (18470), 229
(21869). EIMS m/z (%): 318 (60), 273 (7), 241 (8), 183 (80), 136 (100), 105 (67), 77 (47), 71
(42), 43 (27).
7-Hydroxy-2,2-diphenyl-4H-naphtho[2,3-d][1,3]dioxin-4-one (Nd)
To an ice-cold suspension of 3,7-dihydroxy-2-naphthoic acid (5.0 g, 24.5 mmol) in
trifluoroacetic acid (23 mL) were added trifluoroacetic anhydride (18 mL) and benzophenone
(6.68 g 49 mmol). The mixture was warmed slowly to room temperature and then stirred for
24 h. The mixture was then concentrated on the rotary evaporator, poured into a saturated
solution of aqueous NaHCO3, and extracted with three portions of diethyl ether. Collected
extracts were washed with water and brine, dried (MgSO4), and concentrated to leave yellow
solids. Chromatography over silica using 10% EtOAc in hexane as the eluent afforded 1.6 g
(18%) of 3 as yellow solid, mp 267-270 °C)
Preparation of Polystyrene by ATRP (PS-Br)
CuBr (0.25 g, 1.72 mmol), PMDETA (361 L 1.72 mmol), ethyl-2-bromopropionate as an
initiator (225 L, 1.72 mmol), and styrene (20 mL, 172 mmol) were introduced in a Schlenk
tube, and the reaction mixture was degassed by three freeze–pump–thaw cycles and left in
vacuo. The tube was heated at 90 oC in an oil bath and stirred for 45 min. Then the mixture
was diluted with THF, and passed through an alumina column to remove the complex salts.
Precipitation of the polymer was performed in a ten-fold volume of methanol. The solid was
then collected after filtration. (conv %=32, Mn,theo= 3400, Mn,NMR= 3300, Mn,GPC= 3430,
Mw/Mn= 1.06).
Preparation of Benzodioxinone terminated Polystyrene (PS-Bd)
A solution of HDPD (0.19 g, 0.6 mmol) and anhydrous potassium carbonate (1.24 g, 9 mmol)
in acetone (25 mL) were stirred for 3 h. After that time, PS-Br (0.83 g, 0.24 mmol) was added
and the mixture was heated at reflux temperature for 16 h. The reaction mixture was filtered
to remove the salt. Then, the mixture was concentrated on the rotary evaporator
and
precipitated in methanol. The functional polymer was collected by filtration. (0.8 g; yield= 96
%).1H NMR (250 MHz, CDCl3, δ): 7.51 (s, 1H, Ar), 7.25-6.51 (m, 15H, Ar), 6.20-6.05 (m,
2H, Ar), 4.50 (s, 1H, Ph-CH-O), 3.94 (m, 2H, CH3-CH2-O-CO), 1.85-0.92 (m, 10H, CH2CHPh, CH3-CH2-O-CO, CO-CH-CH3).
13
C NMR (250 MHz, CDCl3, δ): δ=176.7, 176.6,
162.8, 161.6, 146.0, 145.7, 145.3, 145.3, 129.7-127.4, 115.4, 107.1, 96.5, 59.9, 46.4, 45.9,
43.8, 40.4, 37.3, 37.2. FT-IR (ATR): ν = 3513, 3026, 2981, 2912, 1731, 1680, 1601, 1492,
1452, 1370, 1181, 1072, 1028, 908, 756 cm-1.
1H
NMR Analysis for ω-Fuctionalization of Polystyrene
The benzylic bromide peak that appears around 4.41 completely disappears and a new peak
around 4.53 ppm corresponding to the benzylic benzodioxinone proton emerges. Furthermore,
new aromatic peaks which appears at 6.04, 6.20 and 7.49 ppm evidences the incorporation of
benzodioxinone structure at the chain end.
Preparation of PS Supported Silica Gel Particles (PS-OSi and PS-NHSi)
The immobilization of polystyrene onto the basic silica (Si-OH) or to amino modified silica
gel particles (Si-NH2) have been performed using the same methodology described
previously. Thus, PS-bd (150 mg) and Si-OH (75 mg, 50% weight percent) was added into a
quartz tube containing dry CH2Cl2 (5 mL). After the polymer is dissolved, the reaction tube
was irradiated at 300 nm for 5h. The solid phase is filtered and washed several times with
CH2Cl2 to remove the unreacted PS-Bd. The polymer supported silica particles (PS-OSi or
PS-NHSi) were dried under vacuum. The FT-IR analysis shows the presence of aromatic C=C
double bond stretching around 1635 cm-1 due to the polystyrene immobilization.
Preparation of Nd-incorporated Silica Gel Particles (Nd-OSi)
Naphtadioxinone is attached on the silica particles using a similar method as described above.
FT-IR (ATR): ν = 3340, 2923, 2850, 1653, 1426, 1376, 1065, 963, 793 cm-1.
Dynamic Light Scattering (DLS) Measurements
Dispersions of Si-OH and PS-OSi particles (0.1 mg ml-1) were prepared in CH2Cl2. 500
measurements with 10 s runs were taken by Malvern Nano-S instrument using CH2Cl2
viscosity as the medium viscosity. Gaussian curves were fitted to the size histograms to find
the average particle size.
AFM Measurements
Dispersions were spin coated on silicon substrates. NT-MDT Solver P47 instrument was used
in tapping mode. Silicon cantilevers having stiffness k ~ 45 N m-1 were used.
SEM Measurements
SEM measurements were carried out with a Zeiss, Gemini Leo 1550 microscope at 3 kV. The
samples were loaded on carbon coated stubs and coated by sputtering with Au/Pd alloy prior
to imaging.
Figures
Figure S1. 1H NMR spectra of PS-Br and PS-Bd
Figure S2. FT-IR spectra of Si-OH, PS-OSi, Si-NH2 and PS-NHSi
Figure S3. The size (diameter) distributions of Si-NH2 (circles) and PS-NHSi (squares)
nanosized particles in CH2Cl2. Solid lines are Gaussian fits to the data.
Figure S4. SEM image of polymer supported silica particles
Figure S5. Excitated state (a) and excimer (b) fluorescence emmisions observed with
dispersions containing different amounts of Nd-OSi particles (1 mg/mL and 4 mg/mL,
respectively) in CH2Cl2
Figure S6. Photographic images of non-modified Si-OH (a) and dispersed PS-OSi (b)
particles in toluene.
Reference
1
A. Hadfield, H. Schweitzer, M. P. Trova, K. Green, Synth. Commun., 1994, 24, 1025.