Preparation of Perfluorosulfonated Ionomer Nanofibers by Solution Blow Spinning.

Hidetoshi Matsumoto,Wataru Takarada,Masahiro Shinkawa,Kazunori Motai,Keita Eguchi,Yuhei Hayamizu,Noboru Ohta,Hiroyasu Masunaga,Minoru Ashizawa

doi:10.3390/membranes11060389

Hidetoshi Matsumoto, Wataru Takarada + Show 7 more

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https://doi.org/10.3390/membranes11060389

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Abstract

In this work, we report the preparation of high-purity perfluorosulfonated ionomer (Nafion) nanofibers (NFs) via solution blow spinning (SBS). Fiber formation in solution jet spinning is strongly dependent on the structure of the spinning solution. Upon adding a small amount of poly(ethyleneoxide) (PEO) as a spinning aid to Nafion dispersion, most of the highly ordered Nafion aggregate disappeared, allowing the stable production of bead-free and smooth high-purity NFs (Nafion/PEO = 99/1) by SBS. The microstructure of the blowspun Nafion NFs differed from that of electrospun NFs. In the blowspun NFs, incomplete microphase separation between hydrophilic (ionic) and hydrophobic domains was observed, but the crystallization of CF2−CF2 chains was enhanced owing to the high extensional strain rate and rapid solidification during SBS. These findings provide fundamental information for the preparation and characterization of blowspun Nafion NFs.

Highlights

Perfluorosulfonated ionomers (e.g., Nafion®, Flemion®, Aciplex®-F) have attracted much attention as polyelectrolyte membranes in various fields, such as polymer electrolyte fuel cells (PEFCs), chlor-alkali cells, and water electrolyzers, owing to their excellent chemical stability and high proton conductivity [1,2,3,4]
The specific viscosity was calculated from the experimental results shown in Figure S3 as ηsp = η0 − ηs ηs where η0 is the zero-shear viscosity, and ηs is the viscosity of the solvent (MeOH)
To the best of our knowledge, this is the first report on preparation of high-purity Nafion NFs by solution blow spinning (SBS)

Summary

Introduction

Perfluorosulfonated ionomers (e.g., Nafion®, Flemion®, Aciplex®-F) have attracted much attention as polyelectrolyte (proton-exchange) membranes in various fields, such as polymer electrolyte fuel cells (PEFCs), chlor-alkali cells, and water electrolyzers, owing to their excellent chemical stability and high proton conductivity [1,2,3,4]. The backbone and pendant ionic groups are completely different in nature; they spontaneously form a microphase-separated structure This structure allows the ionic domain to swell in the presence of water or other solvent molecules, under high humidity conditions. The conductivity increase is due to the orientation of the ionic domains along the NF axis This result clearly indicates that control over the internal structure of the NFs during thin fiber formation improves the properties of the ion-exchangers. Nafion NFs can be used in the form of porous NF mats and/or composites of NF mats and polymer matrices (NF composite membranes) [9] Such NF networks enable the construction of continuous ion transport pathways in the polymer matrices. To enable the stable production of Nafion NFs by ES, water-soluble polymers such as poly(ethylene oxide) (PEO) [15,16], poly(acrylic acid) [17], and poly(vinylpyrrolidone) [18] have been used as spinning aids

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