www.sciencemag.org/cgi/content/full/332/6025/81/dc1 Supporting Online Material for Electrochemically Mediated Atom Transfer Radical Polymerization Andrew J. D. Magenau, Nicholas C. Strandwitz, Armando Gennaro, Krzysztof Matyjaszewski* *To whom correspondence should be addressed. E-mail: km3b@andrew.cmu.edu Published 1 April 2011, Science 332, 81 (2011) DOI: 10.1126/science.1202357 This PDF file includes: Materials and Methods Figs. S1 to S5 References
Supporting Online Material: Electrochemically Mediated Atom Transfer Radical Polymerization Andrew J. D. Magenau, Nicholas C. Strandwitz, Armando Gennaro, and Krzysztof Matyjaszewski Materials and Methods: Materials. Methyl acrylate (MA, 99%, Aldrich) was passed through a column filled with basic alumina prior to use. Copper(II) bromide (CuBr 2, 99.999%, Aldrich), tris[2- (dimethylamino)ethyl]amine (Me 6 TREN, 99%, ATRP solutions), ethyl 2-bromopropionate (EBP, 98%, Aldrich), silver nitrate (AgNO 3, 99.995%, Alfa Aesar), platinum mesh (gauze, 100 mesh, Aldrich), silver wire (Alfa Aesar), tetra(n-butyl)ammonium bromide (TBABr, Aldrich), tetra(n-butyl)ammonium hexaflourophosphate (TBAPF 6, Aldrich), and anhydrous MeCN (99 %, Aldrich) were purchased with the highest purity and used as received. Instrumentation. Molecular weight and M w /M n were determined by gel permeation chromatography (GPC). The GPC was conducted with a Waters 515 HPLC Pump and Waters 2414 Refractive Index Detector using PSS columns (Styrogel 10 2, 10 3, 10 5 Å) in tetrahydrofuran (THF) as an eluent at a flow rate of 1 ml/min at 35 o C. The column system was calibrated with 12 linear polystyrene (M n = 376 ~ 2,570,000). 1 H NMR spectra were obtained in d-chloroform using a Bruker 300 MHz spectrometer with a delay time of 5 seconds. Cyclic Voltammetry. All of the voltammograms were recorded at 25 C with a Gamry Reference 600 potentiostat. A 12 ml solution of 50 % (v/v) MA in MeCN containing 0.094 M TBAPF 6 and 6 mm TBABr supporting electrolyte was prepared using previously dried reagents. To this solution was added first 0.17 ml of a 0.0724 M solution of Cu II Br 2 /Me 6 TREN (1.0 mm), 1
and then 17.3 µl of neat EBP (11.1 mm). Voltammograms were recorded of the MA and MeCN solvent, and after addition of each reagent. Measurements were carried out under a nitrogen atmosphere at a scan rate of 0.5 V s -1 using a platinum disk working electrode and platinum mesh counter electrode. Potentials were recorded versus an Ag + /Ag reference electrode using a 0.1 M AgNO 3 and TBAPF 6 filling solution separated from the working solutions by a porous Vycor tip. ATRP polymerization of methyl acrylate by electrolysis of Cu II Br 2 /Me 6 TREN. Electrolysis experiments were carried out and recorded with a Gamry Reference 600 potentiostat. Prior to each polymerization, the working and counter electrodes were cleaned thoroughly with organic solvents, submerged briefly in fresh aqua regia, rinsed with deionized water, and dried in an oven. A new Ag + /Ag reference electrode was prepared prior to each polymerization, built using conditions as previously described (S1), containing a filling solution of 0.1 M AgNO 3 and 0.1 M TBAPF 6 in MeCN separated from the working solutions by a porous Vycor tip. Electrolysis was conducted in a five neck pear shaped jacket cell maintained at 25 ºC under a slow N 2 purge. To the dried cell was then added 0.4375 g TBAPF 6, 0.0228 g TBABr, 6.0 ml of MeCN, 6.0 ml of MA, 49 µl of a 0.0724 M solution of Cu II Br 2 /Me 6 TREN in MeCN, and 17.3 µl of neat EBP. All liquid reagents were purged with N 2 for 30 minutes prior to addition. Samples were withdrawn periodically for 1 H NMR and GPC analysis for conversion, and molecular weight and distribution determination, respectively. 2
Supporting Figures: (A) 40 I (μa) 20 0-20 (B) 40 I (μa) 20 0-20 -40 Cu II Br 2 /Me 6 TREN -40-1.6-1.2-0.8-0.4 0.0 E (V vs. Ag/Ag + ) -60 Cu II Br 2 /Me 6 TREN + EBP -80-1.2-1.0-0.8-0.6-0.4-0.2 E (V vs. Ag/Ag + ) Figure S1: Cyclic voltammetry of 50 % (v/v) MA in MeCN containing 0.094 M TBAPF 6 and 6 mm TBABr recorded at a Pt electrode recorded at v = 0.5 V/s -1 : (A) blank and (B) 1.0 mm Cu II Br 2 /Me 6 TREN in the absence (black trace) and presence of 0.011 M EBP (blue trace). ln([m] 0 /[M]) 1.00 0.75 0.50 0.25 E (V vs Ag + /Ag) E = -0.72 E = -0.69 E = -0.66 y = 0.927x - 0.045 y = 0.732x - 0.089 y = 0.392x - 0.045 0.00 0.00 0.25 0.50 0.75 1.00 1.25 time (h) Figure S2: First order kinetic plot with respect to time, as a function of applied potential. Linear fitting applied to determine apparent rate constants (k app ). Polymerizations conducted in 50% (v/v) MA in MeCN at 25 C. [MA] 0 = 5.55 M; [MA] 0 :[EBP] 0 :[Me 6 TREN] 0 :[Cu II Br 2 ] 0 = 500:1:0.025:0.025. 3
E = -0.72 V conversion (%) 14 32 46 56 69 76 83 91 95 10 3 10 4 10 5 molecular weight Figure S3: Evolution of molecular weight with monomer conversion observed in GPC at -0.72 V versus Ag + /Ag. E = -0.66 V conversion (%) 6 13 22 30 42 55 65 80 86 10 3 10 4 10 5 molecular weight Figure S4: Evolution of molecular weight with monomer conversion observed in GPC at -0.66 V versus Ag + /Ag. 4
conversion (%) 10 12 18 28 33 44 49 62 10 3 10 4 10 5 molecular weight Figure S5: Evolution of molecular weight with monomer conversion observed in GPC at -0.69 and -0.40 V versus Ag + /Ag. Supplementary References: S1. C. G. Zoski Handbook of Electrochemistry (Elsevier 2007), pp. 93-94. 5