Synthesis and characterization of crosslinked polymer nanocomposite for polymer electrolyte materials

Novel nanocomposite membranes based on sulfonated poly(arylenethioethersulfone) and polysiloxane-network were prepared via an in situ sol–gel process. The polysiloxane-network (PSIN) as nanostructure was formed by dimethyldimethoxysilane (DMDMS), tetraethoxysilane (TEOS), and N,N-diethylaminopropyltrimethoxysilane (DAPMS). Sulfonated poly(arylenethioethersulfone) (SPTES-100) polymer was modified to reduce its water absorption by the in situ formation of polysiloaxane-network. DAPMS was introduced as a bonding agent to improve the interaction between the two phases: hydrophilic phase (SPTES-100 polymer) and hydrophobic phase (PSIN) in the nanocomposites. PSIN/SPTES-100 nanocomposite membranes with 5 wt% PSIN content had lower water uptake compared with SPTES-100 polymer and exhibited controlled swelling up to 75 °C. TGA studies indicated that nanocomposite membranes established the good thermal stability. Proton conductivity of the nanocomposite membranes with 5 wt% PSIN was measured under 85% relative humidity conditions up to 85 °C, which shows proton conductivity is higher than that of SPTES-50 copolymer and Nafion 117. SEM cross-sectional features showed that the PSIN particles were uniformly embedded in the membrane matrix and the average domain size was ∼500 nm. It is noticeable that the improvement in proton conductivity was mainly due to the uniform dispersion of the PSIN particles throughout the membrane matrix, thus establishing continuous conduction pathways in the nanocomposite membranes.