Self-supporting, Hydrophobic, Ionic Liquid-Based Reference Electrodes Prepared by Polymerization-Induced Microphase Separation

Transcription

1 Supporting Information Self-supporting, Hydrophobic, Ionic Liquid-Based Reference Electrodes Prepared by Polymerization-Induced Microphase Separation Sujay A. Chopade, Evan L. Anderson, Peter W. Schmidt, Timothy P. Lodge, *,, Marc A. Hillmyer,*, and Philippe Bühlmann*, Department of Chemical Engineering and Materials Science and Department of Chemistry, University of Minnesota, Minneapolis, MN Corresponding Authors Timothy P. Lodge, Marc A. Hillmyer, Philippe Bühlmann, S-1

2 1. PMMA-CTA characterization PMMA-b-PS PMMA-CTA 40 kg/mol detector signal Elution Volume (ml) Figure S1. SEC chromatograms of PMMA-CTA (40 kg/mol, Ð = 1.08) and linear PMMA-b- PS (Ð = 1.2) diblock polymer. Complete end-functionalization in PMMA-CTA was confirmed through the controlled growth of PMMA-b-PS linear diblocks, as indicated by the shift to higher molecular weight. S-2

3 Chemical shift (ppm) Chemical shift (ppm) Figure S2. 1 H NMR (CDCl 3, 500 MHz) spectrum of PMMA-CTA. S-3

4 2. PIMS reference electrode preparation and composition (a) rubber septum aluminum cap glass vial AgCl coated Ag wire PIMS reaction precursor (b) AgCl coated Ag wire self- supporting PIMS reference electrode Ag wire encapsulated within polymer/il composite (c) (d) 1 cm Figure S3. (a) Sealed vials used to prepare PIMS reference electrodes. A AgCl-coated Ag wire was inserted through the rubber septum and suspended in the reaction mixture. (b) Selfsupporting PIMS reference electrode obtained by breaking the glass vial. The Ag wire is firmly encapsulated within the PIMS polymer/il composite. (c) Setup used to design thin PIMS samples for mechanical testing. Sample thickness was determined by the Teflon separator thickness. (d) PIMS/C8-IL sample, thickness = 0.4 mm, was used to design S-4

5 rectangular tensile bars for mechanical testing. The RAFT-CTA imparts the yellow color to the reaction mixture and the PIMS reference electrodes. Table S1: Composition of PIMS reference electrodes PIMS/C 8 -IL (40% IL content) Mechanically robust phase (cross-linked PS) Composition (% w/w) Ionic liquid Conducting phase (PMMA + IL) Composition (% v/v)* Ionic liquid Mechanically robust phase (cross-linked PS) Conducting phase (PMMA + IL) PIMS/C 8 -IL (50% IL content) *Composition was calculated based on the following densities (g/cm 3 ): ρ PSDVB = 1.05, ρ PMMA = 1.18, ρ C8-IL = Except for the SAXS experiments, the composition of PIMS reference electrodes was 50 wt% IL content. S-5

6 3. Impedance spectroscopy 10 5 Z' Z'' Impedance (Ω) PIMS/[C 8 mim][ntf 2 ] Frequency (Hz) Figure S4. Representative impedance data for a PIMS/C 8 -IL polymer composite sample collected at 25 C. Squares ( ) are Z, circles ( ) are Z. The red line denotes the bulk resistance, R, used to calculate the conductivity. Measurements were performed over the frequency range from 1 MHz to 1 Hz. S-6

7 4. Electrode potentials in KCl electrolyte solutions Figure S5. EMF of PIMS/C 8 -IL, PIMS/C 12 -IL, P(VdF-co-HFP)/C 8 -IL reference electrodes as a function of mean K + /Cl activity. Left-most points for PIMS/C 8 -IL and PIMS/C 12 -IL are EMF values in deionized, purified water (18.2 MΩ cm specific resistance). EMF values were measured against a conventional reference electrode with a free-flowing double junction. All EMF values are corrected for liquid junction potentials at the conventional reference electrode. PIMS/C 8 -IL, PIMS/C 12 -IL error bars represent the standard deviation in the EMF of three reference electrodes samples, respectively. S-7

8 5. Comparison of PIMS and free-flow double junction reference electrodes Figure S6. EMF of a AgCl-coated Ag wire in KCl solutions of varying mean Cl activity measured against PIMS/C 8 -IL, PIMS/C 12 -IL, and free-flow double-junction reference electrodes. Potentials measured using the free-flow double-junction reference electrode are corrected for liquid junction potentials. 6. P(VdF-co-HFP)/C 8 -IL gel reference electrodes AgCl coated Ag wire P(VdF- co- HFP)/C 8 - IL gel (trimmed to achieve uniform thickness) Bottom tip sealed with commercial silicone sealant Figure S7. P(VdF-co-HFP)/C 8 -IL gel reference electrodes were prepared by sequential gel deposition onto a Ag wire. The gel deposit was trimmed using a razor blade to achieve a uniform thickness. To compensate for the poor gel coverage at the bottom tip of the wire, commercial silicone sealant was used to insulate the tip. S-8

9 7. Mechanical properties Stress (MPa) Mechanical phase - 41% v/v Strain (%) Figure S8. Stress-strain curves for three PIMS/C 8 -IL (50% w/w IL content) samples. indicate break points. S-9

10 8. Thermal properties T decomposition = 350 C 80 Weight (%) PIMS/C 8 IL (50 wt% IL content) heating rate: 10 C/min Temperature ( C) Figure S9. Thermogravimetric curve of the PIMS/C 8 -IL sample (50 wt% IL content) under nitrogen (heating rate: 10 C/min). The sample decomposed at 350 C. Normalized Heat Flow (W/g) 0.1 W/g -72 C -73 C 114 C PMMA-CTA PMMA + C 8 IL PIMS/C 8 -IL Temperature ( C) Figure S10. DSC thermograms for PMMA-CTA, PMMA+C 8 -IL, and PIMS/C 8 -IL composites. The traces represent the second heating cycle (exothermic flow down). The IL plasticizes the conducting phase of the PIMS polymer/il composite. S-10

11 9. Control over the geometry of the PIMS reference electrodes The PIMS design strategy permits control of the shape of reference electrodes. The easy-toprocess liquid reaction precursor undergoes polymerization and simultaneous in-situ crosslinking, thereby solidifying to adopt the shape of the reaction container or mold. In the current study, glass molds were obtained by use of the bottom section (approximately 3 cm) of nuclear magnetic resonance (NMR) spectroscopy tubes (5 mm outer diameter). The reaction mixture was poured into the glass mold, which was then sealed using a rubber septum. (a) 1 cm AgCl coated Ag wire Teflon heat shrink PIMS polymer/il composite (b) Figure S11. (a) PIMS reference electrode samples prepared using glass vials (see Figure S3). (b) Samples prepared using NMR tube glass molds. S-11