Fluoropolymers proton conductivity

For instance, the Dow experimental membrane and the recently introduced Hyflon Ion E83 membrane by Solvay-Solexis are "short side chain" (SSC) fluoropolymers, which exhibit increased water uptake, significantly enhanced proton conductivity, and better stability at T > 100°C due to higher glass transition temperatures in comparison to Nafion. The membrane morphology and the basic mechanisms of proton transport are, however, similar for all PFSA ionomers mentioned. The base polymer of Nation, depicted schematically in Figure 6.3, consists of a copolymer of tetrafluoro-ethylene, forming the backbone, and randomly attached pendant side chains of perfluorinated vinyl ethers, terminated by sulfonic acid head groups. °... 

As described previously, Nafion membranes exhibit much higher proton conductivity than any other aliphatic and aromatic PEMs bearing similar ion content due to the special chemical structure and morphology. Partially sul-fonated polystyrene (SPS) and PTFSSA have the same backbone except PTF-SSA possesses a fluoropolymer backbone. The dependence of proton conductivity on EW for SPS at 22 °C [172] and PTFSSA [138] membranes is shown in Fig. 17. The conductivities of the fluorinated block copolymer P(VDF-co-... 

To enhance membrane mechanical and hydro-thermal stability, Jiang et al. prepared a blend of side-chain sulfonated PFCB block copolymer and a PVDF fluoropolymer [129]. The chemical structure of the side-chain sulfonated PFCB ionomer is shown in Scheme 6.32. They evaluated the membrane s fiandamental properties, such as proton conductivity, gas permeability, water uptake, and... 

Fluoropolymers can be readily processed into membranes which have found applications in ultrafiltration, microfiltration, wastewater treatment, protein adsorption and separation, proton conduction, stimuli-responsive and controlled deliveries, and biotechnology [6-10]. However, the practical applications of fluoropolymer membranes are limited to some extent by their hydrophobic and inert surface properties. 

FUNCTIONAL FLUOROPOLYMER FOR PROTON-CONDUCTIVE COMPOSITE MEMBRANES... 

As a substimte to Nafion impregnation into a fluoropolymer matrix, solution cast films have been prepared from blends of Nafion and vinylidene fluoride-hex-afluoropropylene copolymer [16]. Upon addition of 20 60% vinylidene copolymer, a steep decrease in proton conductivity was observed, from 10 " S cm to 10 -10 S cm , which was accompanied by a significant decrease in methanol permeability. In a more recent paper [27], Si et al. solution cast membranes composed of Nafion and poly(vinylidene fluoride), henceforth denoted as PVDF, where characterized where the PVDF content was varied from 0 to 65 wt%. As expected, the conductivity and methanol permeability decreased with inaeasing PVDF content, with a much more dramatic drop in transport parameters when the PVDF content was >50%. From proton conductivity and methanol permeability data, the relative selectivity can be determined ... 

The first proton-conducting perfluorinated membrane carrying phosphonic acid units was prepared by Kotov et al. [34]. Several co- and ter-fluoropolymers based on tetrafluoroethylene and perfluorovinylenes, such as... 

Proton Exchange Membrane (PEM), commonly synonymous with DuPont s Nation membrane and used in both PEM fuel cells and DMFCs, requires aqueous conditions for suitable ionic conductivity and therefore needs insulation against freezing, and requires rigorous humidity control. Although other membrane chemistries are available, the sulfonated tetrafluoroethylene-based fluoropolymer-copolymer chemistry used in Naflon and other brand name membranes is still the material of choice. 

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