Polysiloxane modified hybrid membranes were prepared by introducing pre-swelled commercial
Nafion membrane into a sol-gel precursor solution, consisting of a pre-hydrolyzed mixture of
tetraethoxysilane (TEOS) and a mercaptan functionalized organoalkoxysilane. The structure of the
polysiloxane network was changed by altering the ratio of the two silane components within the
precursor solution. The mercaptosilane modifier was used to provide an additional source of acidic
Bronsted sites through the oxidisation of the mercaptan groups to sulfonic acid groups.
The physical and chemical properties of the hybrid membranes were examined by TGA, FTIR and
SEM analysis. The water vapour sorption and proton conductivity characteristics were evaluated at
temperatures up to 70°C and with water activity in the region of 0.4 to 1.
It was found that the polysiloxane network alters the water vapour sorption mechanism of the
Nafion membrane, resulting in an increase in the equilibrium amount of water absorbed in the
middle range of water activity (0.4-0.6). At the same time, the increased water absorption capability
produced a concomitant increase in ionic conductivity at low water activities
