Effect of nanodiamonds with different surface states on ion channel packing and proton conductivity of composite perfluorosulfone membranes

A copolymer of the Aquivion${}^\circledR$ type was modified with detonation diamonds (size 4–5 nm, concentration 0.25–5.0 wt.%) and studied using neutron scattering, measuring the packing period of ion channels in the matrix. Positively charged diamonds with a hydrogen-saturated surface at a concentration of 0.5 wt.% provided a 30% increase in the ionic conductivity of the membranes at a temperature of 50$^\circ$C due to compaction of the packing of channel assemblies. Due to the electrostatic attraction of the components, a more developed conductive diamond-copolymer interface was created in such membranes than in composites with negatively charged ionic groups of the components. When the matrix was filled with hydrophobic fluorinated diamonds (1 wt.%), a fivefold decrease in ionic conductivity was observed due to the disruption of the connectivity of ion channels. The found correlations between the structure and ionic conductivity of the composites depending on the type and amount of filler are important for the targeted formation of membranes upon modification with nanoparticles.