Vibrational Spectroscopy for the Determination of Ionizable Group Content in Ionomer Materials.

An approach based on vibrational spectral measurements is described for determining the ionizable group content of ion conducting polymer membrane materials. Aimed at supporting the assessment of membrane stability and wear characteristics, performance is evaluated for attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, confocal Raman microscopy, and ATR FT-IR microscopy using perfluorinated ionomer membrane standards. One set of ionomer standards contained a sulfonic acid ionizable group and the other a sulfonyl imide group.

The effect of low-molecular-weight poly(ethylene glycol) (PEG) plasticizers on the transport properties of lithium fluorosulfonimide ionic melt electrolytes.

The influence of low-molecular-weight poly(ethylene glycol) (PEG, Mw ≈ 550 Da) plasticizers on the rheology and ion-transport properties of fluorosulfonimide-based polyether ionic melt (IM) electrolytes has been investigated experimentally and via molecular dynamics (MD) simulations. Addition of PEG plasticizer to samples of IM electrolytes caused a decrease in electrolyte viscosity coupled to an increase in ionic conductivity. MD simulations revealed that addition of plasticizer increased self-diffusion coefficients for both cations and anions with the plasticizer being the fastest diffusing species.

Trifluoromethylation of perfluorinated diacylfluorides: synthesis of the diketone CF3C(O)CF2C(O)CF3 and of new perfluorinated diol (CF3)2C(OH)CF2C(OH)(CF3)2.

Perfluoromalonyl difluoride reacts with TMS-CF3 (1:1) in the presence of KF to give the new diketone CF2(C(O)CF3)2. A large excess (5:1) of TMS-CF3 results in the presumed potassium dialkoxide [(CF3)2COK]2CF2 which yields the 1,3-ditertiarydiol [(CF3)2C(OH)]2CF2 on reaction with H2SO4.

Thermal processing as a means to prepare durable, submicron thickness ionomer films for study by transmission infrared spectroscopy.

A high temperature solution processing method was adapted to prepare durable, freestanding, submicrometer thickness films for transmission infrared spectroscopy studies of ionomer membrane. The materials retain structural integrity following cleaning and ion-exchange steps in boiling solutions, similar to a commercial fuel cell membrane. Unlike commercial membrane, which typically has thicknesses of >25 μm, the structural properties of the submicrometer thickness materials can be probed in mid-infrared spectral measurements with the use of transmission sampling.

Syntheses of a perfluoroethanesulfonyl fluoride vinyl ether.

The target monomer, perfluoroethanesulfonyl fluoride vinyl ether 8, was obtained from the starting material, iodoperfluoroethanesulfonyl fluoride 1, through the intermediate, acyl fluoride 4. Two different synthetic routes were utilized in the conversion of 4 to 8.

Effect of perfluoroalkyl chain length on proton conduction in fluoroalkylated phosphonic, phosphinic, and sulfonic acids.

The effects of increasing perfluoroalkyl chain length on the molecular properties of viscosity, diffusivity, and ionic conductivity of a series of acid model compounds analogous to comb-branch perfluorinated ionomers functionalized with phosphonic, phosphinic, and sulfonic protogenic groups are reported. Anhydrous proton transport by a Grotthuss-like hopping mechanism was observed to occur efficiently in phosphorus-based fluoroalkylated model acids but only when there is a relatively low perfluoroalkyl content. The decrease in degree of dissociation of the protogenic groups follows the order phosphonic > phosphinic > sulfonic, and the degree of dissociation and the magnitude of ion-ion correlations are approximately independent of chain length.

Perfluoroalkyl phosphonic and phosphinic acids as proton conductors for anhydrous proton-exchange membranes.

A study of proton-transport rates and mechanisms under anhydrous conditions using a series of acid model compounds, analogous to comb-branch perfluorinated ionomers functionalized with phosphonic, phosphinic, sulfonic, and carboxylic acid protogenic groups, is reported. Model compounds are characterized with respect to proton conductivity, viscosity, proton, and anion (conjugate base) self-diffusion coefficients, and Hammett acidity. The highest conductivities, and also the highest viscosities, are observed for the phosphonic and phosphinic acid model compounds.

Infrared spectroscopy of bis[(perfluoroalkyl)sulfonyl] imide ionomer membrane materials.

Structural properties of the proton-exchanged forms of bis[(perfluoroalkyl)sulfonyl] imide (PFSI) ionomer materials were investigated. The hydration and dehydration of samples prepared as thin films and freestanding membrane were probed by applying transmission infrared spectroscopy. Spectral bands were assigned and effects of water incorporation into membrane pores and channels were understood by drawing upon results from related measurements performed on the structurally similar, perfluorosulfonic acid ionomer, Nafion.

Fluoroalkylation of imidazoles by hypervalent iodonium salts.

N-1H,1H-perfluoroalkylation and regioselective C-perfluoroalkylation of imidazoles were obtained using the corresponding hypervalent iodonium salts.

Construction of N-1H,1H-perfluoroalkylated peptide bonds.

The preparation of a variety of optically pure peptides containing an N-1H,1H-perfluoroalkyl label on a selected backbone amide bond is now possible.

Transport properties of solid polymer electrolytes prepared from oligomeric fluorosulfonimide lithium salts dissolved in high molecular weight poly(ethylene oxide).

Transport properties such as ionic conductivity, lithium transference number, and apparent salt diffusion coefficient are reported for solid polymer electrolytes (SPEs) prepared using several oligomeric bis[(perfluoroalkyl)sulfonyl]imide (fluorosulfonimide) lithium salts dissolved in high molecular weight poly(ethylene oxide) (PEO). The salt series consists of polyanions in which two discrete fluorosulfonimide anions are linked together by [(perfluorobutylene)disulfonyl]imide linker chains. The restricted diffusion technique was used to measure the apparent salt diffusion coefficients in SPEs, and cationic transference numbers were determined using both potentiostatic polarization and electrochemical impedance spectroscopy methods.

NMR and IR studies of bis((perfluoroalkyl)sulfonyl)imides.

The influence of water on the NMR and IR spectra of bis((perfluoroalkyl)sulfonyl)imides has been investigated. The large effects of water on the observed spectra suggest that the proton is predominantly bound to the nitrogen of the perfluorosulfonimide acid in the absence of water, while it protonates water to form an onium salt in the presence of water.

Rubidium bis(trifluoromethanesulfonyl)imidate dioxane disolvate.

The bis(trifluoromethanesulfonyl)imidate anion crystallizes with Rb as the title dioxane 1:2 solvate, Rb(+).CF(3)SO(2)NSO(2)CF(3)(-).2C(4)H(8)O(2), with the anion in a transoid conformation, as opposed to the cisoid form typically seen when there are significant cation-anion interactions.

A novel 1,3,5-tris(alpha,beta,beta-trifluorovinyl)benzene monomer.

The reaction of the perfluoroalkenylzinc reagent, CF2=CFZnBr, with 1,3,5-tribromobenzene in the presence of a catalytic amount of Pd(Ph3)4 yielded a novel trifunctional monomer 1,3,5-tris(alpha,beta,beta-trifluorovinyl)benzene (1).

Direct methylation and trifluoroethylation of imidazole and pyridine derivatives.

Direct methylation or trifluoroethylation of imidazole and pyridine derivatives using N-methyl bis((perfluoroalkyl)sulfonyl)imides or trifluoroethyl phenyliodonium bis((trifluoromethyl)sulfonyl)imide affords high yields of the corresponding salts. This methodology provides a simple route to a variety of room temperature ionic liquids (RTILs).

Selective Epoxidation of Olefins by Perfluoro-cis-2,3-dialkyloxaziridines(1).

Alkyl-substituted olefins are epoxidized by perfluoro-cis-2,3-dialkyloxaziridines under particularly mild conditions. Electron deficient substrates (e.g.

Synthesis and Reaction Chemistry of the Disodium Alkoxide of 2,6-Bis(trifluoromethyl)-2,6-dihydroxy-3,3,4,4,5,5-hexafluorooxane.

The disodium alkoxide of 2,6-bis(trifluoromethyl)-2,6-dihydroxy-3,3,4,4,5,5-hexafluorooxane, C(7)F(12)O(3)Na(2), 1, was prepared by reaction of the corresponding diol with MeONa in MeOH. This cyclic alkoxide readily mimics the reaction chemistry of the lithium and sodium alkoxides of perfluoropinacol. The reaction of the alkoxide 1 with covalent dichlorides and metallocene dichlorides yields a series of novel bicyclic ring systems.