Polymer electrolyte fuel cells (PEFC) are expected as next energy generation systems, and their performance is strongly dependent upon the polymer electrolyte membrane (PEM). We have suggested a new model of PEM with a three-dimensional proton conduction passways structure using the filler method, particularly focused on the functionalization of filler particles. The polymer surface-functionalized silica nanoparticles (NPs) with three different particle sizes were prepared by the reversible addition–fragmentation chain transfer polymerization with particles (RAFT PwP) method that we developed. Silica NPs coated with an in situ polymerized block copolymer consisted of a proton conductive polymer and a protective polymer. We confirmed that the proton conductivity increased and the activation energy decreased as the core particle size became smaller because of enlarging the total interface area between each particle and increasing the proton conduction passways.

We have successfully demonstrated a polymer electrolyte membrane (PEM) composed of core-shell type nanoparticles (NPs) which are silica NPs coated with poly(acrylic acid)-b-polystyrene (PAA-b-PS). In this work, for further improvement of proton conductive performance, we focus on the relationship between the coating amount of PAA and proton conduction performance. The PAA coating amount can be facilely controlled by changing the polymerization conditions. With the optimized PAA coating amount, the proton conductivity shows 9.2 × 10 −4 S cm −1 at 60 °C and 98% relative humidity with low activation energy (E a = 0.33 eV). In addition, with coating PS on

Low-acidity polymer electrolyte membranes are essential to polymer electrolyte fuel cells (PEFCs) and water electrolysis systems, both of which are expected to be next-generation energy and hydrogen sources. We developed a new type of highperformance polymer electrolyte membrane (PEM) in which the core particles are precisely electrolyte polymer coated and filled into binder resin. Cellulose nanocrystals (CNCs), which have attracted attention as light, rigid, and sustainable materials, were selected as the core material for the filler. The CNC surface was coated with a new block copolymer containing a proton conductive polymer of poly(vinylphosphonic acid) (PVPA) and a hydrophobic polymer of polystyrene (PS) using RAFT polymerization with particles (PwP) we developed. The pelletized fillers and the filler-filled polycarbonate membranes achieved proton conductivities of over 10 −2 S/cm with lower activation energies and much weaker acidity than the Nafion membrane.

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Polymer electrolyte membrane fuel cells (PEMFC) have the challenges of operation under low humidity conditions caused by the proton conduction mechanism dependent on water. We focused on polymeric ionic liquids (PIL), which are promising for high proton conductivity under the wide range environment because of having the characteristic of the polymer electrolyte liquid. However, it is difficult to fabricate the self-standing membrane of PIL due to the high hygroscopicity and fluidity. In this paper, to inhibit the fluidity of PIL developing the self-standing polymer electrolyte membrane (PEM), the hydrophobic chain segment of styrene is inserted between PIL of poly(vinylphosphonic acid/1-propylimidazole) (P(VPA/1PIm)) by RAFT polymerization. The synthesized sample of P(VPA/1PIm)-block-polystyrene (P(VPA/1PIm)-b-PS) is potentially applicable to PEM materials because it is obtained in a powder state, having the high heat resistance of up 300°C, and performing the proton-conducting property under the wide range environment.