RAFT Polymerization of an Intrinsically Stretchable Water-Soluble Block Copolymer Scaffold for PEDOT

Transcription

1 Supporting Information for RAFT Polymerization of an Intrinsically Stretchable Water-Soluble Block Copolymer Scaffold for PEDOT Laure V. Kayser, Madeleine D. Russell, Daniel Rodriquez, Sami N. Abuhamdieh, Charles Dhong, Salik Khan, Alexander N. Stein, Julian Ramírez, Darren J. Lipomi* *Author to whom correspondence should be addressed: Experimental Section General Number-average (M n ) and weight-average (M w ) molecular weights and polydispersity Ð were determined by Agilent Technologies 1260 Infinity II LC system running in 30 % methanol and 70 % 0.2 M NaNO 3, 0.01 M NaH 2 PO 4 in water at ph 7 (adjusted with concentrated NaOH) at 40 C at 1 ml min 1, using a PL aquagel-oh Mixed-B column, and calibrated against narrow polydispersity polystyrene sulfonate standards (purchased from Polymer Standards Service). 1 H NMR were acquired on a 300 MHz Bruker or a 500 MHz Jeol instruments in D 2 O at room temperature. Samples of PEDOT were spin-coated on gold-coated, diced silicon squares of 1 cm 1 cm at a spin speed of 500 rpm (250 rpm s 1 ramp) for 120 s followed by 2000 rpm (1000 rpm s 1 ramp) for 30 s and annealed at 120 C for 15 min. These sample were used for both AFM and SEM. The AFM images were acquired in a tapping mode (Scanning Probe Microscope, Veeco) in a 1 µm 1 µm scanning area at a rate of 1 Hz. The SEM images were taken using an FEI Apreo ultra high resolution scanning electron microscope. S-1

2 Aminolysis and Stability of the Trithiocarbonate Functional Group in PSS-b-PPEGMEA-b-PSS The aminolysis of the trithiocarbonate was performed following a procedure by Li et al. 1 PSS-b-PPEGMEA-b-PSS (100 mg, 0.66 µmol) was dissolved in 5 ml of water and degassed under a nitrogen flow for 30 min. 2-ethanolamine (10 µl, 0.13 mmol) and tributylphosphine (1 µl, 4 µmol) were then added through a septum using a syringe. The reaction mixture was left to stir for 18 h at room temperature, over the course of which the solution went from yellow to colorless. SEC triblock: M n = 82.4 kda, M w = kda, Ð = 1.5, SEC after aminolysis (PSS-b- PPEGMEA): M n = 38.1 kda, M w = 68.5 kda, Ð = 1.7. The stability of the trithiocarbonate under the reaction conditions used for the PEDOT oxidative polymerization was tested by subjecting PSS-b-PPEGMEA-b-PSS to the same conditions but without EDOT monomer. PSS-b-PPEGMEA-b-PSS was dissolved in water (50 mg/ml) and stirred over an acidic resin (Dowex Marathon C hydrogen form) for 18 h at room temperature. The acidified polymer was filtered through a 1 µm filter. To 10 ml of this solution, sodium persulfate (454 mg, 2.3 wt eq.) and iron trichloride (0.11 ml of 10 wt% solution) were added. The reaction was stirred at room temperature for 24 h (SEC (triblock after oxidation ): M n = 44.6 kda, M w = 80.7 kda, Ð = 1.8). The reaction mixture was subsequently stirred over 10 ml of acidic (Dowex Marathon C hydrogen form) and 7 ml of basic (Lewatit MP-62 free base) resins for 6 h then filtered through a 10 µm filter (SEC (triblock after oxidation and work-up): M n = 40.5 kda, M w = 71.9 kda, Ð = 1.8). S-2

3 Figure S1. SEC traces of PSS-b-PPEGMEA-b-PSS (triblock) before and after aminolysis (PSSb-PPEGMEA diblock) and comparison with the SEC traces of the triblock polymer after oxidation and oxidation and work-up (addition of acidic and basic resins). Preparation of Samples for Conductivity Measurements Glass slides were cut into 4 cm squares with a diamond-tipped scribe. The slides were then successively washed in Alconox solution (2 mg ml -1 ), deionized water, acetone, and isopropyl alcohol (IPA) in an ultrasonic bath for 10 min each and dried with compressed air. The glass slides were then plasma treated at ~30 W for 3 min at a pressure of 200 mtorr under ambient air to remove any residual organic material and activate the surface. The PEDOT solutions were spin-coated onto glass slides at a spin speed of 500 rpm (250 rpm s 1 ramp) for 120 s followed by 2000 rpm (1000 rpm s 1 ramp) for 30 s. After spin-coating the samples were annealed on a hotplate at 120 C for 15 min in air. The PEDOT thin films were wired using two copper wires and carbon paint (DAG-T-502) to a Keithley 2400 sourcemeter and the resistance was measured. The thickness of the films was measured using a Veeco Dektak 150 stylus profilometer to convert the resistance to conductivity. The conductivity σ was calculated as an average conductivity of 3 samples as per the following equation: S-3

4 Table S1. Tabulated thin-film dimensions and resistance for each formulation (3 separate resistance measurements) Sample Width w (cm) PEDOT:PSS PEDOT:PSS:PPEGMEA 2.3 PEDOT:PSS-b- PPEGMEA With 5 wt% DMSO With 5 wt% glycerol 2.4 With 1 wt% glycerol 2.3 Length l (cm) 2.4 Thickness t (nm) Resistance R (kω) Tensile Tests PEDOT films were drop casted onto Teflon or PTFE sheets and left to dry in a desiccator containing drierite for 24 to 48 h at room temperature. The films were then fully dried on a hot plate at 120 C for 15 min prior to mechanical testing. The free-standing films were then peeled off the substrate and cut into rectangles using a razor blade. The films were placed in grips attached to a force gauge and the stress was measured as a function of strain (strain rate = 1 mm min 1 ). For some samples, the resistance was measured simultaneously, in which case the films were connected to a sourcemeter using copper wires and carbon paint. The fatigue tests were S-4

5 conducted in a similar manner (strain rate = 1 mm min 1 ) for 200 strain/release cycles within the elastic regime of the sample. Table S2. Tabulated film dimensions for each formulation (3 separate tensile tests) Sample Width (mm) Length (mm) Thickness (mm) PEDOT:PSS PEDOT:PSS:PPEGMEA PEDOT:PSS-b-PPEGMEA With 5 wt% DMSO With 1 wt% glycerol S-5

6 Supplementary Figures Figure S2. AFM height images of spin-coated PEDOT thin films. Top: PEDOT:PSS, PEDOT:PSS:PPEGMEA and PEDOT:PSS-b-PPEGMEA. Bottom: PEDOT:PSS-b-PPEGMEA with 5 wt% DMSO, 5 wt% glycerol and 1 wt% glycerol additives. S-6

7 Figure S3. SEM images of spin-coated PEDOT thin films of PEDOT:PSS, PEDOT:PSS:PPEGMEA and PEDOT:PSS-b-PPEGMEA neat and PEDOT:PSS-b-PPEGMEA with 5 wt% DMSO, 5 wt% glycerol and 1 wt% glycerol additives. S-7

8 Figure S4. Microscope images of a PEDOT:PSS-b-PPEGMEA spin-coated thin film (~ 300 nm) damaged with a razor blade and after the addition of water and drying in two different areas. Figure S5. 1 H NMR of PSS in D 2 O. S-8

9 Figure S6. 1 H NMR of PSS-b-PPEGMEA-b-PSS in D 2 O. Figure S7. 1 H NMR of PPEGMEA in D 2 O. S-9

10 References 1. Li, M.; De, P.; Gondi, S. R.; Sumerlin, B. S., End group transformations of RAFTgenerated polymers with bismaleimides: Functional telechelics and modular block copolymers. J. Polym. Sci., Part A: Polym. Chem. 2008, 46 (15), S-10