Conductometric Analysis for the Formation of Poly(Vinylidene Fluoride)-Based Ion Track Membranes

Abstract

Poly(vinylidene fluoride) (PVDF) films were irradiated with 450 MeV 129 Xe and 2.2 GeV 197 Au ion beams, and then the resulting latent tracks were etched in a 9 mol dm -3 aqueous KOH solution at 80ºC that had been poured into a conductometric cell. At the same time, the evolution of cylindrical nanopores was monitored by measuring the conductance through the membrane. This in-situ measurement enabled us to examine how the etching kinetics were affected by the various experimental conditions including the parameters (mass and velocity) of the bombarded ions and cell voltages applied between the electrodes. The track etch rate, V T , radial etch rate, V R , and pore radius reaching the final plateau significantly depended on the deposited energy within each track, which is represented by the linear energy transfer (LET). Interestingly, applying a higher voltage to the cell promoted track etching up to the breakthrough probably because the electrophoretic migration of dissolved products occurred out of each pore.

Radiation-Grafted Membranes for Polymer Electrolyte Fuel Cells: Current Trends and Future Directions

“…This made it possible to establish the relationship between the etching kinetics under various experimental conditions. 190 Similar PEM pore-filled membranes were obtained by the irradiation, with swift heavy ion-beams, of 129 Xe 23+ followed by γ-ray irradiation, then grafting of St onto the ETFE films followed by sulfonation as shown in Figure 26. A proton conductivity of 110 mS cm −1 was achieved when measured in the thickness direction.…”

“…The evolution of the cylindrical nanopores formed in these membranes was monitored by the in situ measurement of the conductance through the membrane. This made it possible to establish the relationship between the etching kinetics under various experimental conditions …”

“…The durability of radiation-grafted PEMs was found to vary significantly depending on the starting polymeric materials, the composition of the monomer system, the RIG technique employed, reaction parameters, and not least the method of assembling the membrane with the electrodes. ,,− A number of new preparative routes for introducing substantial improvements in the stability of the desired PEMs have been proposed. These include three main strategies: (i) the grafting of alternative monomers such as m , p -methylstyrene or vinyltoluene, , p - tert -butylstyrene, vinylbenzyl chloride, , p -styryltrimethoxysilane, , methyl acrylate, and 2-bromotetrafluoroethyl trifluorovinyl ether and monomer combinations such as styrene/α-methylstyrene, styrene/acrylonitrile, styrene/methylacrylnitrile, ,,, styrene/acrylic acid, ,, styrene/methyl methacrylic acid, α-methylstyrene/methylacrylnitrile, , styrene/glycidyl methacrylate, , styrene/trimethoxysilylpropyl methacrylate, and methyl acrylate/methyl methacrylate; (ii) the introduction of new or modified substrate films for grafting of styrene or its derivatives with or without cross-linkers such as cross-linked PTFE, ,,,,,,,− engineering plastics such as poly­(ether ether ketone), ,− polyimide, , polyether sulfone, alicyclic polybenzimidazole, polymer powder (e.g., UHMWPE or PVDF) followed by thermal treatment, − or solution casting, porous films, ,,,​ − and nanofibrous mats; and finally (iii) the application of n...…”

“…Hence, more research is definitely needed to establish the preparation procedures, through optimization of the grafting and sulfonation parameters before fuel cell performance and stability investigations can be completed. The replacement of substrates having random pores with alternative ones having regular cylindrical nanopores (track etched films) obtained by irradiation with swift heavy ions is an attractive approach for further controlling the transport properties. − The resulting PEMs deserve further investigation with respect to preparation, characterization, and fuel cell testing. The porous substrates can be also replaced by nanofibrous polymer films, which can be obtained by electrospinning techniques.…”