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1 Metallocene-containing Homopolymers and Heterobimetallic Block Copolymers via Photoinduced RAFT Polymerization Peng Yang, Parasmani Pageni, Mohammad Pabel Kabir, Tianyu Zhu and Chuanbing Tang* Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina, 29208, United States Supporting Information EXPERIMENTAL SECTION Materials. Tris[2-phenylpyridinato-C 2,N]iridium(III) (fac-[ir(ppy)3], 99%), ferrocenylmethyl methacrylate (FeMMA) and RAFT chain transfer agent (CTA): 2- (dodecylthiocarbonothioylthio)-2-methylpropionic acid (DTPA), cumyl dithiobenzoate (CDB) were all purchased from Sigma Aldrich. Methyl methacrylate (MMA) was purchased from Sigma Aldrich and freshly distilled before use. Triethylamine, N-(3- dimethylaminopropyl)-n-ethylcarbodiimide hydrochloride (EDC-HCl, 98%), sodium hexafluorophosphate, 2-aminoethyl methacrylate hydrochloride (90%), 4- (dimethylamino)pyridine and 2-hydroxyethyl acrylate were purchased from VWR International. N,N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO) dichloromethane (DCM), tetrahydrofuran (THF) and acetonitrile (MeCN) were dried and freshly distilled. Deionized water was used in all experiments when needed. S1

2 Characterization. 300 MHz 1 H NMR spectra were recorded on a Varian Mercury 300 spectrometer with tetramethylsilane (TMS) as an internal reference. Gel permeation chromatography (GPC) was performed in dimethylformamide (DMF, containing 0.1% LiBr) at a flow rate of 0.8 ml/min at 50 C on a Varian system equipped with a ProStar 210 pump and a Varian 356- LC RI detector and three 5 μm phenogel columns (Phenomenex Co.) with narrow dispersed polystyrene as standards. Hitachi 8000 transmission electron microscope was applied to take TEM images at an operating voltage of 150 kv. TEM samples were prepared by dropping solution on carbon-supported copper grids and then dried before observation. Dynamic light scattering (DLS) was performed on a submicrometer particle sizer (Autodiluter Model 370, Particle Sizing Systems, Inc., Santa Barbara, CA) at a scattering angle of 90. Synthesis of Cobaltocenium and Ferrocene Monomers. Cobaltocenium monomer 2- cobaltoceniumamidoethyl methacrylate hexafluorophosphate (CoAEMA) was synthesized using an amidation reaction. 1 A typical procedure was as follows: Cobaltocenium carboxylic acid hexafluorophosphate (10 g, mmol), 4- (dimethylamino) pyridine (0.65 g, 5.30 mmol), and 2-aminoethyl methacrylate hydrochloride (4.70 g, mmol) were dissolved in DCM (100 ml) at 0 o C. Then, N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (5.50 g, 28.7 mmol) was slowly added into reaction followed by dry triethylamine (8.0 g, 79.0 mmol). The solution was stirred for 6 hours at room temperature and then extracted by sodium hexafluorophosphate saturated aqueous solution for three times. The organic phase was S2

3 collected, condensed and precipitated into cold diethyl ether. After drying under vacuum overnight, 9.0 g of yellow cobaltocenium monomer was obtained with an overall yield of 65%. 1 H NMR (DMSO-d6, δ, ppm): 8.87 (t, NHCH2, 1H), 6.25 (t, Cp, 2H), (m, CH2C, 2H), 5.95 (t, Cp, 2H), 5.80 (s, Cp, 5H), 4.25 (m, OCH2CH2NH, 2H), 3.54 (m, OCH2CH2NH, 2H), 1.87 (m, CH3CCO, 3H). Ferrocene monomer 2-(methacryloyloxy)ethyl ferrocenecarboxylate (MAEFe) was synthesized according to a previous report. 2 1 H NMR for MAEFe (CDCl3, δ, ppm): (d, CH2C, 2H), 4.75 (s, Cp, 2H), 4.35 (s, Cp, 2H), 4.20 (m, O CH2CH2O, 4H), 4.15 (s, Cp, 5H), 1.75 (m, CH3CCO, 3H). Synthesis of Cobaltocenium Homopolymer PCoAEMA via Photoinduced RAFT Polymerization. Monomer CoAEMA (500 mg, 1.02 mmol), Ir(ppy)3 (0.065 mg, mmol) and different RAFT chain transfer agents 2-(dodecylthiocarbonothioylthio)- 2-methylpropionic acid (DTPA, 4.15 mg, 0.01 mmol) or cumyl dithiobenzoate (CDB, 2.73 mg, 0.01mmol) were dissolved in 1.0 ml of DMSO or DMF in a 10 ml Schlenk flask and then degassed by purging N2 for 30 min. The mixture was covered in aluminum foil and then irradiated by a blue LED strip (4.8 Watts, λ max = 435 nm) at different temperatures (25, 60 or 90 o C) for 24 h. The reaction was quenched by turning off the light and cooling with ice-water. After reaction, the mixture was precipitated in cold DCM for three times and vacuum-dried. In a typical procedure without deoxygenation, CoAEMA (500 mg, 1.02 mmol) and DTPA (4.15 mg, 0.01 mmol) were dissolved in 1.0 ml of DMSO in a 10 ml Schlenk flask. Different amounts of photo catalyst Ir(ppy)3 were tried (1.3 mg, 0.65 mg, 0.3mg, 0.15 mg and mg) to initiate S3

4 polymerization. We found the minimum amount of catalyst to achieve the success of the polymerization was about 0.3 mg. 1 H NMR (DMSO-d6, δ): 8.87 (t, NHCH2), 6.32 (t, Cp), 5.95 (t, Cp,), 5.80 (s, Cp), 4.00 (m, OCH2CH2NH), 1.87 (m, CH3CCO), (broad, CH3). Synthesis of Ferrocene Homopolymer PMAEFe via Photoinduced RAFT Polymerization. Monomer MAEFe (345 mg, 1.02 mmol), Ir(ppy)3 (0.065mg, mmol) and DTPA (4.15 mg, mmol) were dissolved in 1.0 ml of THF in a 10 ml Schlenk flask and then degassed by purging N2 for 30 min. The mixture was covered in aluminum foil and then irradiated by a blue LED strip (4.8 Watts, λ max = 435 nm) at room temperatures or 60 o C for 24 h. The reaction was quenched by turning off the light and cooling with ice-water. After reaction, the mixture was precipitated in cold methanol for three times and vacuum-dried. 1H NMR for MAEFe (CDCl3, δ, ppm): 6.12 (m, CH2C), 5.50 (m, CH2C), 4.75 (m, Cp), 4.35 (m, Cp), 4.20 (m, O CH2CH2O), 4.15 (m, Cp), 1.75 (m, CH3CCO), (broad, CH3). Chain Extension to Prepare PMAEFe-b-PMMA Diblock Copolymers. The diblock copolymer PMAEFe-b-PMMA was prepared by using PMAEFe as a macro-cta (Scheme 1). A typical procedure was as follows: homopolymer PMAEFe (7000g/mol, 70 mg, 0.01 mmol), Ir(ppy)3 (0.065mg, mmol) and MMA (500mg, 5 mmol) were dissolved in 2.0 ml THF in a 10 ml Schlenk flask and degassed by purging N2 for 30 min. The mixture was covered in aluminum foil and then irradiated by a blue LED strip (4.8 Watts, λ max = 435 nm) at 60 o C for 24 h. The reaction was quenched by turning off the light and cooling with ice-water. After reaction, the mixture was S4

5 precipitated in cold methanol for three times and vacuum-dried. Synthesis of Heterobimetallic Diblock Copolymer PCoAEMA-b-PMAEFe. The synthesis of diblock copolymer PCoAEMA-b-PMAEFc was followed a similar procedure with PMAEFe-b-PMMA. PCoAEMA (12000 g/mol, 120 mg, 0.01 mmol), Ir(ppy)3 (6.5 mg, mol) and MAEFc (1.02 g, 3.00 mmol) were dissolved in 2 ml of DMSO in a 10 ml Schlenk flask and degassed by purging N2 for 30 min. The mixture was covered in aluminum foil and then irradiated by a blue LED strip (4.8 Watts, λ max = 435 nm) at 60 o C for 24 h. The reaction was quenched by turning off the light and cooling with ice-water. After reaction, the mixture was precipitated in cold methanol for three times and vacuum-dried. The reaction mixture was precipitated in cold diethyl ether three times and vacuum-dried to yield a yellow solid. Kinetic Studies of Polymerization for Homopolymers and Diblock Copolymers. All kinetic studies followed a similar procedure. For example, CoAEMA (500 mg, 1.02 mmol), Ir(ppy)3 (6.5 mg, mol) and DTPA (4.15 mg, mmol) were dissolved in 1.0 ml of DMSO in a 10 ml Schlenk flask and then degassed by purging N2 for 30 min (the degassed step was not needed for kinetic studies of photoinduced polymerization under air). The mixture was covered in aluminum foil and then irradiated by a blue LED strip (4.8 Watts, λ max = 435 nm) at 60 or 90 o C. Samples were taken out at different intervals when the light was turned on or off. The conversion of monomers was calculated by 1 H NMR. S5

6 Scheme S1. Chemicals used in this study. Metallocene monomers: 2-cobaltocenium amidoethyl methacrylate hexafluorophosphate (CoAEMA), ferrocenylmethyl methacrylate (FeMMA) and 2-(methacrylolyoxy)ethyl ferrocenecarboxylate (MAEFe); chain transfer agents: cumyl dithiobenzoate (CDB) 2-(dodecylthiocarbonothioylthio)- 2-methylpropionic acid (DTPA); Photocatalyst: fac-[ir(ppy)3]. S6

7 c Figure S1. A photo of the experimental apparatus. The crystallizing dish (diameter: 150 mm. height: 75mm) with silicone oil was wrapped by the 4.8 W blue LED light strip (length=3 m, λ= 430 nm). The Schlenk flask (10 ml) with reaction mixture was placed in the center of crystallizing dish. S7

8 Figure 2: (Top) NMR spectrum of crude reaction mixture of cobaltocenium polymerization, the experimental ratio of [M]:[CTA]:[Ir] is 100:1:0.01; (Bottom) An expanded region from the left spectrum. The crude NMR of cobaltocenium polymerization was used to verify the conversion and determine the molecular weight Mn,NMR. The peak at 6.25 ppm, corresponding to the two protons (f) of cyclopentadienyl (Cp) rings, was used as standard. The change of integration of proton (a) of double bond at 6.10 in the reaction mixture (compared to monomer only) was used to calculate the conversion. S8

9 a) b) Figure S3. Photoinduced RAFT polymerization of CoAEMA using CDB as CTA and fac-[ir(ppy)3] as photocatalyst under 4.8 W blue LED irradiation at 90 o C: 1H NMR spectra of (a) cobaltocenium monomer CoAEMA and (b) cobaltocenium polymer PCoAEMA. S9

10 24 h 15 h 5 h 2.5h Retention Time (min) Figure S4. Photoinduced polymerization of MAEFe using DTPA as CTA at 60 o C: GPC traces at different time of exposure under continuous light irritation. The experimental ratio of [M]:[CTA]:[Ir] is 100:1:0.01. REFERENCES (1) Zhang, J.; Yan, J.; Pageni, P.; Yan, Y.; Wirth, A.; Chen, Y.-P.; Qiao, Y.; Wang, Q.; Decho, A. W.; Tang, C. Sci. Rep. 2015, 5, (2) Hardy, C. G.; Ren, L.; Tamboue, T. C.; Tang, C. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, S10