Quaternized Polynorbornene Random Copolymers for Fuel Cell Devices

Abstract

Quaternized polymers are critical components for various energy devices. Vinyl-addition polynorbornenes provide high mechanical strength, high ion conductivity, and chemical stability in a wide range of pH environments due to the all-C–C bond backbone. Herein, we present the synthesis of a series of quaternized polynorbornene random copolymers via vinyl addition polymerization and elucidate the impact of polymer composition on their properties. The quaternary ammonium alkyl tether length and the ratio of n-hexylnorbornene to unsubstituted norbornene are systemically tailored. A copolymer of 5-(3-bromopropyl)-2-norbornene and norbornene with pendant trimethylammonium groups achieved hydroxide conductivity of 109 mS/cm at 80 °C with a modest water uptake of 72%. The addition of n-hexylnorbornene to the copolymer, to make a terpolymer, allows for the polymer composition to be tailored for properties, including a decrease in water uptake and higher processability, despite a slightly decreased hydroxide conductivity. Moreover, the developed membranes are chemically robust and highly mechanically stable, enabling thin membranes to be easily fabricated. This study provides insight into important design parameters for quaternized polynorbornenes for a variety of energy storage and conversion devices, especially fuel cells.

Comparing Ammonium and Tetraaminophosphonium Anion-Exchange Membranes Derived from Vinyl-Addition Polynorbornene Copolymers

“…10,16 The conductivity of the 67:33 PNB-Hex-NMe 3 [OH] AEM reported here is reasonably close to the conductivity of a similar polymer reported by Saito, Kim, and co-workers. 10 In that work, they synthesized a NB-5-Hex, norbornene, and 5-bromopropylnorbornene terpolymer, which was converted into a trimethylammonium-based AEM (σ 80°C = 68 mS/cm). 10 The conductivity of the PNB-Hex-NMe 3 [OH] copolymers described here are roughly half compared to the random copolymers reported by Kohl and co-workers which is not surprising since the IEC's of the copolymers reported here are lower (1.38−2.19 mmol/g).…”

Rapid Postgrafting Reaction to Prepare Quaternized Polycarbazoles

“…Under H 2 /O 2 conditions, the open circuit voltage of the cell reached >1.0 V. The peak power density was 1.35 W cm –2 . The HFR of the cell was ∼0.065 Ω cm 2 , slightly higher than the cell using state-of-the-art AEMs (0.04 Ω cm 2 ) Figure B shows the AEM water electrolyzer performance of PDPC-6QA (membrane thickness = 35 μm under pure water-fed conditions.…”

“…The HFR of the cell was ∼0.065 Ω cm 2 , slightly higher than the cell using state- of-the-art AEMs (0.04 Ω cm 2 ). 25 Figure 4B shows the AEM water electrolyzer performance of PDPC-6QA (membrane thickness = 35 μm under pure water-fed conditions. A decent performance of 0.25 and 0.34 A cm −2 at 1.9 V was achieved at 60 and 80 °C, respectively.…”

Hydrocarbon Ionomeric Binders for Fuel Cells and Electrolyzers

“…Saito and co‐workers prepared polynorbornene‐based thin film electrodes by utilizing norbornene and alkyl bromonorbornene to improve the solubility of the ionomer. [ 215 ] The soluble ionomer (IEC = 2.5 meq. g −1 ) has a balanced hydroxide conductivity (137 mS cm −1 at 80 °C), moderate water uptake (95% at 80 °C), enabling high AEMFC (Figure 13c) and AEMWE performance.…”