Composite membranes, consisting of
Nafion and inorganic
oxide additives, are frequently discussed alternative materials to overcome the known low conductivity of pure
Nafion at temperatures above 100 °C and at low relative humidity. It has been reported that under dry conditions, these membranes show enhanced water uptake and diffusion as compared to filler-free
Nafion. This work focuses on the
polymer mobility in
Nafion/SiO(2) composites and on the impact of the
silica particles on the
polymer dynamics. [
Nafion/(SiO(2))(X)] composite membranes (with X ranging from 0 to 15 wt%) in the dry and wet states were investigated by variable temperature solid-state (19)F NMR spectroscopy. (19)F T(1) and T(1ρ) relaxation times, and NMR lineshapes (linewidths and spinning sideband intensities) were analyzed to get information about the
polymer mobility. It is found that
Nafion composite membranes, in general, possess a higher mobility as compared to recast
Nafion which is in agreement with previous results from conductivity studies. These findings are attributed to the ability of the SiO(2) particles to keep more water inside the composite membranes which also leads to a higher mobility of the
polymer component. The results are further supported by the experimental (19)F{(1)H} CP/MAS NMR spectra. It is also shown that the structure of the composite membranes is more stable after
dehydration, and possible condensation reactions are diminished in these membranes. In addition, the decrease in ionic exchange capacity after
dehydration is less pronounced for the composite membranes as compared to filler-free
Nafion.