Inorganic modification of block copolymer for medium temperature proton exchange membrane application

Abstract

New hybrid membranes have been developed via sol–gel chemistry and solvent directed infiltration method using novel inorganic precursors and sulfonated poly(styrene-b-[ethylene-co-butylene]-b-styrene) (S-SEBS). S-SEBS shows a distinct phase separated morphology which can be used as a structure directing template to drive the inorganic component within the ionic domains of the polymer. Photoacoustic Fourier transform infrared spectroscopy (PA-FTIR) confirms the formation of Si–O–Si and Si–O–P bridges in hybrid membranes which indicate a silicate or phosphosilicate network structure within the hybrid membranes. The presence of the inorganic network within the hybrid membranes improves their thermal stability, viscoelastic properties and water retention at elevated temperatures above 100°C. Scanning electron microscopy (SEM) results show a uniform distribution of the inorganic component within the hybrid membranes and confirm successful incorporation of inorganic particles within S-SEBS membranes. Conductivity of S-SEBS starts to decrease after 60°C due to excessive swelling whereas hybrid membranes show an increase in conductivity after 60°C as the inorganic component reduces excessive swelling in hybrid membranes. SAXS results indicate that S-SEBS has distinct phase separated morphology and show hybrid membranes exhibit a lamellar morphology. © 2010, Elsevier Ltd.