Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2008. Supporting Information for Macromol. Rapid Commun., 2008, 29, 1538.
Hydrated Clay for Catalyst Removal in Copper Mediated Atom Transfer Radical Polymerization
Selvaraj Munirasu, Ashwini Deshpande, Durairaj Baskaran*
Division of Polymer Science and Engineering, National Chemical Laboratory, Pune411008, India E-mail:
[email protected]
Methods and Materials The reagents such as CuBr, CuBr2, N, N,N’,N’,N”-pentamethyldiethylenetriamine (PMDETA), tetrahydrofuran (THF, HPLC grade), ethyl-2-bromoisobutyrate (BrEiB) and dry anisole were purchased from Aldrich, USA and used without further purification. Monomers such as methyl methacrylate (MMA), benzyl methacrylate (BnMA) were purchased from Aldrich (USA) and passed through basic alumina column (Aldrich, USA) in order to remove the inhibitor. Sodium montmorillonite (Na-clay) was obtained from Southern Clay Products (USA). Size exclusion chromatography (SEC) performed using GPC-TQ instrument equipped with two detectors (UV and RI) and two 60 cm PSS SDV-gel columns: 1 x 10µ/100 Å, 1 x 10µ/linear: 102-106 Å. THF was used as eluent at the rate of 1 mL min-1. The
calibration of SEC was performed using monodispersed polystyrene standards from PSS Germany. Before SEC analysis, the polymers were passed through a short basic alumina column in THF in order to remove any tiny solid materials present in the polymer (such as clay fragments and residual catalyst etc). Atomic adsorption spectroscopy (AAS) was performed using GBC-Avanta instrument. For copper analysis, 327.4 nm wavelength with lamb current of 4.00 mAmp was used and the instrument was calibrated using 0.5, 5 and 10 ppm standard copper solutions. The WAXD experiments were performed using a Rigaku Dmax 2500 diffractometer equipped with a copper target and a diffracted beam monochromator. (Cu Kα radiation with λ = 1.5406 Å) with a 2θ scan range of 2-10° at room temperature.
PerkinElmer Lambda 950 UV/VIS spectrometer was used for
measurement of copper leaching and a known concentration of CuBr-PMDETA solution in chloroform was used for the calibration at λmax = 660 nm.
ATRP of BnMA and MMA in anisole at room temperature in the presence and absence of hydrated Na-clay The polymerization of BnMA and MMA was carried out in the presence and absence of dry and hydrated Na-clay. Some reactions were performed in the absence of externally added deactivator. Actual concentrations of the reagents were taken as given the Table 1. A typical ATRP was performed as given below: In a dry schlenk tube, a required amount of monomer (5 mL BnMA), 5 mL of dry anisole, 0.0085 g of CuBr (0.059 mmol), 0.013 g CuBr2 (0.059 mmol) (some reactions were performed in the absence of CuBr2), and 0.025 mL of PMDETA (0.118 mmol) was taken and degassed using a freeze-pump-thaw cycle. A known quantity of Na-clay (0.165 g) and a small amount of water (0.03 mL) was
added into the reaction under nitrogen flux. The reaction mixture was degassed using three freeze-pump-thaw cycle and filled with nitrogen. To this solution, a required amount of inititator, BrEiB (0.0087 mL, 0.059 mmol) was added to commence the polymerization and the tube was closed using a natural rubber septa. The heterogeneous reaction mixture was stirred for a known period of time (4-6 h) and the reaction was quenched by exposing to air. The polymerization solution was diluted with 20 mL of toluene and stirred for 30 min (in some cases, ~ 1 h) in air. The catalyst absorbed Na-clay was filtered using 0.2 µm Teflon membrane. The colorless filtrate solution containing polymer was recovered either by evaporation or precipitation in excess n-hexane. The polymer was dried at 60° C under vacuum for 4 h. The monomer conversion was calculated on the basis of yield determined by gravimetry.
Leaching studies of CuBr-PMDETA loaded hydrated Na-clay in anisole For the determination of maximum absorption of copper-ligand complex on hydrated Naclay surface in anisole, CuBr-PMDETA loaded clay with various amounts of copper from 0.5 to 3.0 moles equivalent to sodium ion in clay were prepared. In a typical reaction, a required amount of Cu(I)Br (50 mg, 0.3486 mmol) was charged in a clean and dry schlenk tube followed by the addition of 20 mL dry anisole. To this, 73 µL of PMDETA (0.3486 mmol) was added to make a homogeneous copper-PMDETA complex.
A
required amount of Na-MMT (760 mg) clay and 200 µL of de-ionized water were added and the reaction mixture was stirred for a while under nitrogen. Then, the reaction mixture was filtered through 0.1 µm Teflon membrane immediately without exposing too
much time to the atmospheric air. In another identical reaction, the reaction mixture was exposed to air and stirred for 30 min. The filtrate was collected in a round bottom flask and the solvent was removed using rotary evaporator followed by applying high vacuum. The copper-ligand loaded Na-clay was recovered from the filter membrane. Similarly, different amounts of CuBr-PMDETA loaded Na-clay were made. In the case of copper trapping under N2, the solid content was weighed gravimetrically to calculate the leached copper content. For the open-air reaction, atomic adsorption spectroscopy (AAS) and UV-Visible spectroscopy were used for the quantification of leach out copper.
i) PBnMA in the presence of dry clay Mn,SEC = 171,700 g/mol Mw/Mn = 2.40 Cu/Clay = 10 %
ii) PBnMA in the presence of hydrated clay Mn,SEC = 35,700 g/mol
Mw/Mn = 1.56 Cu/Clay = 5 %
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Figure S1. SEC traces of poly(n-benzyl methacrylate)s synthesized in the presence of i) insitu dried CuBr-clay mixture (catalyst was removed by passing through alumina column) and ii) in the presence of moist Na-clay (H2O/clay = 10 wt %).
i) PMMA in presence of Na-Clay Cu/Clay = 8 wt % Mw/Mn = 1.70
ii) PMMA- normal ATRP (post clay addition) Cu/Clay = 8 wt % Mw/Mn = 1.15 Mn,th/Mn,SEC = 0.98
Mn,th/Mn,SEC = 0.84
[Cu]polymer = 1.74 ppm
[Cu]polymer = 1.63 ppm
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Figure S2. ATRP of MMA i) in the presence of hydrated Na-clay and ii) in the absence of clay and catalyst was removed after the polymerization by adding Na-clay and water.
