Sulphonated poly(ether ether ketone) copolymers: Synthesis, characterisation and membrane properties

Novel sulphonated poly(ether ether ketone) (PEEK) copolymers with controlled degree of sulphonation were synthesized by polycondensation reaction of varying ratios of silylated phenolphthalein, silylated biphenol, 5,5′-carbonyl-bis(2-fluoro benzene sulphonate) (sulphonated 4,4′-difluorobenzophenone) and 4,4′-difluorobenzophenone. The structure of the copolymers was confirmed by using ATR and 1H NMR techniques. Molecular mass of these samples was determined by GPC. Thermal stability of the samples was evaluated using TGA technique. Methanol diffusion coefficients were in the range of 6.57 × 10−8 to 2.5 × 10−6 cm2/s. The proton conductivity of the membranes in the temperature range of 25–75 °C was found to be 10−5 to 10−3 S/cm.