Synthesis of original para‐sulfonic acid aminoethylthioethylbenzenesulfonic by telomerization, and its grafting onto poly(VDF‐co‐HFP) copolymers for proton exchange membrane for fuel cell

Abstract

The synthesis of a novel aromatic sulfonic acid bearing an amino function H2NC2H4SC2H4C6H4SO3Na (1) from the radical addition of mercaptoethylamine hydrochloride onto styrene sodium sulfonate, and its subsequent grafting onto poly(vinylidene fluoride‐co‐hexafluoropropylene), poly(VDF‐co‐HFP), copolymer are presented. First, the radical telomerization, carried out under radical conditions and in water, led to various products [monoadduct (1), multiadducts, and polymers], the amounts of which depend on the experimental conditions and [mercaptan]0/[monomer]0 initial molar ratio (R0). An R0 ≥ 1 led to the monoadduct (1) only and achieved in ∼85% yield. The zwitterionic isomer was obtained mainly and its chemical modification was possible to get an original aromatic sodium sulfonate containing an amino end group. A kinetic study of the telomerization was presented for R0 < 1. Thermogravimetric analysis of the telomer showed that this compound was stable up to 200 °C. Second, the grafting of (1) onto poly(VDF‐co‐HFP) copolymer was also investigated. Such a grafting proceeded as expected by a classic mechanism of grafting of amines. Molar percentages of grafted telomer were assessed by 1H NMR spectroscopy and by elemental analysis. Ion exchange capacity (IEC) values of the membranes were deduced from the mol % grafted telomer. Scanning electron microscopy pictures showed a good homogeneity in the cross‐section of membranes, and energy dispersive X‐ray evidenced that all SO3Na groups of the grafted amine were changed into SO3H after treatment with concentrated HCl. Method involving an impedance analyzer, working at increasing high frequencies was used to assess the protonic conductivities, σ. These values were lower than that of Nafion117®, but σ increased with the IEC to 0.4 mS/cm at room temperature and 95% relative humidity. Water and methanol uptakes were also assessed, and it was shown that σ increased when water uptakes increased. Membranes started to decompose from 170 °C under air. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 121–136, 2009

Unexpected Radical Telomerisation of Vinylidene Fluoride with 2-Mercaptoethanol

“…That efficient transfer step can explain that remaining radicals, arising from unreacted initiator, are able to initiate the homopolymerisation of VDF, leading to PVDF. That observation was already noted in the radical telomerisation of styrene with mercapto-2-ammonium chloride that also generated polystyrene next to monoadduct telomer [38].…”

Building bridges: Crosslinking of sulfonated aromatic polymers—A review

“…Compared to the former, direct polymerization of various monomers can endow SAP with the desired structure and a controlled degree of sulfonation, tailor the property-structure relationship, and make XL reactions more versatile [50,[60][61][62][63][64][65]. In the following, various crosslinking pathways are considered.…”

Synthesis and characterization of high molecular weight hexafluoroisopropylidene‐containing polybenzimidazole for high‐temperature polymer electrolyte membrane fuel cells

“…The hexafluoroisopropylidene group is widely used to improve high performance polymers such as polyimides and polyamides without sacrificing the high performance 26. Alternate PBI approaches and new directions in fluorinated polymers for fuel cell membranes have also been explored in recent years 27–36. The introduction of hexafluoroisopropylidene group into the polymer backbone increases the solubility, thermal stability, flame resistance, oxidation resistance, and so forth while decreasing the crystallinity, dielectric constant, water absorption, and color.…”