Copolymers of ethylene and sulfonated norbornene for proton exchange membranes

Abstract

Terpolymers of ethylene, norbornene, and 5-exo norbornene methyl alcohol are prepared using Pd phosphine sulfonates as catalysts. The pendant hydroxyl groups are then transformed into thioacetate groups. Films cast from the resulting polymers are then oxidized by hydrogen peroxide. This green oxidation method is found to quantitatively transform thioacetate groups into sulfonic acids, leading to the formation of sulfonated hydrocarbon ionomers. These ionomers are thermally stable, exhibit increasing conductivity up to 110 C, and have a low water uptake, indicating that these materials are potentially interesting candidates for the preparation of fuel cell membranes. remain a limiting element in the development of this technology. Currently, the most plausible candidate for a massproduced PEM is NafionV R , a perfluorinated polymer with sulfonic acid as pendant group. 1 An unique feature of Nafion is the microphase separation between the hydrophobic backbone and the hydrated sulfonic acid domains, resulting in the formation of water channels for the transport of protons.2 However, this fluorinated ionomer is expensive and its production requires stringent conditions. Additional drawbacks of Nafion include high methanol permeability, low conductivity at temperatures higher than 100 C and at low relative humidity, and poor mechanical stability at elevated temperature. The search for better PEMs for proton exchange fuel cells remains a challenge for scientists despite a plethora of articles regarding this issue.

Quaternized Polynorbornene Random Copolymers for Fuel Cell Devices

“…Molecular weights are similar to reported values using the trans-[Ni(C 6 F 5 ) 2 (SbPh 3 ) 2 ] catalyst, 32,33 and higher than polymers synthesized with a palladium-based catalyst system. 34,40,41 Random copolymers were synthesized by utilizing norbornene (NB) and an alkyl bromonorbornene, BMN, BPN, or BHN to form PBMN, PBPN, and PBHN polymers (Figure 1b). The terpolymers were synthesized using NB, BPN, and HN.…”

Synthesis and Applications in Catalysis of Metal Complexes with Chelating Phosphinosulfonate Ligands

“…119 It can be noted here that methacrylates were not incorporated in the presence of the same catalysts and mainly homopolyethylene was formed. 125 Similarly, vinylic monomers such as vinyl ethers, 56 vinyl acetate, 126 norbornene derivatives 48,127 were copolymerized with ethylene. Among them, acrylic acid, 120,121 acrylamides, 62,122 acrylonitrile, 51,123 vinyl sulfones, 124 vinyl chloride, 57 and vinyl fluoride.…”