This paper presents a preparation route which allows the formation of a poly(phenylene) ionomer containing merely sulfone units (-SO 2 -) connecting the phenyl rings and in which each phenyl ring is monosulfonated (100% degree of sulfonation). This corresponds to an ion exchange capacity (IEC) of 4.5 mequiv g -1 (equivalent weight of EW ) 220 g equiv -1 ). The preparation succeeded in a two-step process comprising a polycondensation reaction of sulfonated difluorodiphenyl sulfone with sodium sulfide, yielding sulfonated poly(phenylene sulfide sulfone), and the subsequent oxidation to the corresponding sulfonated poly(phenylene sulfone). The polymer was characterized by elemental analysis, NMR, IR, GPC, viscosity measurement, TGA in air and in pure water vapor atmosphere, DSC at low and high temperatures, and ac impedance spectroscopy. Room temperature water absorption isotherms have been determined by equilibrating samples at different relative humidities. Under the chosen reaction conditions, polymers with molecular weights up to M w ≈ 61 000 g mol -1 were obtained, corresponding to intrinsic viscosities up to 0.73 dL g -1 . The water-soluble ionomer exhibits a very high density (F ) 1.75 g cm -3 in the dry form), no glass transition or melting temperature, and a very high thermooxidative and hydrothermal stability. The latter is attributed to the specific molecular structure consisting of extremely electron-deficient aromatic rings. At high temperature (T ) 110-160 °C) and low relative humidities (rh ) 50-15%) the proton conductivity exceeds that of Nafion by a factor of 5-7.

Vitreous samples were prepared in the (100 - x)% NaPO(3)-x% MoO(3) (0

Poly(phenylene) ionomers which contain merely sulfone units (-SO(2)-) connecting the phenyl rings and in which each phenyl ring is sulfonated (-SO(3)H) have been characterized with respect to their microstructural and transport properties. The high degree of sulfonation leads to the development of a microstructure characterized by very narrow hydrated, hydrophilic domains which are well connected on longer scales. These features together with high absolute water uptakes at given relative humidities and the high charge carrier concentration corresponding to the high ion exchange capacity (IEC approximately 4.5 milli equivalent g(-1)) result in very high proton conductivities but also low water transport coefficients (water diffusion and presumably also electroosmotic drag and permeation). Compared to the transport properties of Nafion, these trends increase with increasing water content and with increasing temperature. For a relative humidity of RH = 30% and a temperature of T = 135 degrees C, the proton conductivity is found to be seven times higher than the conductivity of Nafion under the same conditions. Highly sulfonated poly(p-phenylene sulfone) polymers are water soluble and brittle in the dry state, but their transport properties together with their high hydrolytical and morphological stability renders this type of ionomer an interesting constituent of polymer electrolyte membrane (PEM) fuel cell membranes able to operate at high temperature and low humidification.

A family of multiblock copolymers consisting of alternating fully sulfonated hydrophilic poly(phenylene sulfone) and hydrophobic poly(phenylene ether sulfone) segments are prepared and characterized. The multiblock copolymers are formed by the coupling of preformed hydrophilic and hydrophobic blocks using a specially designed coupling agent. The block lengths (degree of polymerization) of both segment types were varied in order to control the ion exchange capacity. Solution cast films show spontaneous nanophase separation leading to distinct bicontinuous morphologies with correlation lengths around 15 nm. The hydrophobic phase gives the membranes their advantageous viscoelastic properties even at high temperatures under both wet and dry conditions, while proton conductivity takes place within the hydrophilic phase. Since the properties of fully sulfonated poly (phenylene sulfone)s are locally preserved within the hydrophilic domain, the membranes show very high proton conductivity and high hydrolytic stability. The very high degree of water dispersion within the hydrophilic domains leads to very low electro‐osmotic water drag. Because of their superior transport and stability properties these multiblock copolymers have a great potential for use as a substitute for perfluorosulfonic acid membranes which are used as separator materials in electrochemical applications such as polymer electrolyte membrane (PEM) fuel cells and redox flow batteries.

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