Sulfonated Polybenzothiazoles: A Novel Candidate for Proton Exchange Membranes

Abstract

Sulfonated polybenzothiazoles (sPBT) with high molecular weight as well as excellent solubility were synthesized for the first time, which was achieved by attaching the phenylsulfonyl pendant groups or incorporating the hexafluoroisopropylidene moieties to the polymer backbone. Such sulfonated polybenzothiazoles thus could be cast into homogeneous membranes and could be further evaluated as proton exchange membranes. These sPBTs showed high thermal stability and high proton conductivity as well as low swelling. For instance, the hexafluoroisopropylidene-containing sPBT with a disulfonation degree of 65% exhibited a T d5 of 380 °C, a proton conductivity of 0.11 S/cm, and a swelling of 15.5% at 80 °C. In addition, the sPBT membranes showed excellent oxidative and hydrolytic stability. In comparison with the phenylsulfonyl pendant-group-containing sPBT membranes, the hexafluoroisopropylidene-containing sPBT membranes with an equivalent ion exchange capacity showed much narrower ionic channels because of the hydrophobic hexafluoroisopropylidene moieties. This made the latter display better dimensional stability, oxidative stability, and hydrolytic stability than the former. This investigation illustrated that sulfonated polybenzothiazoles are a novel candidate for proton exchange membranes.

Mixed-gas CO2/CH4 and CO2/N2 separation with sulfonated PEEK membranes

“…According to experiences with proton exchange membranes (PEM), the sulfonated groups aggregate into hydrophilic clusters, which can provide ionic transport channels, while the aromatic backbone, responsible for the mechanical and thermal stability of the resulting membranes, are represented by the hydrophobic clusters. The distribution of these two regions greatly affects the membrane performance [27,28].…”

Hexafluoroisopropylidene based sulfonated new copolytriazoles: investigation of proton exchange membrane properties

“…Therefore, many efforts have been made in order to replace these materials. Several hydro carbon basedsulfonated aromatic PEM materials, such as sulfonated poly(arylene ether sulfone)s (9)(10)(11)(12)(13)(14)(15), sulfonated poly(arylene ether ketone)s (16)(17)(18)(19), sulfonated polyimides (20)(21)(22)(23)(24)(25), sulfonated poly(benzimidazole)s (26)(27)(28), sul fonated polybenzothiazoles (29)(30)(31) and sulfonated poly triazoles (32)(33)(34)(35)(36)(37), have been developed in the recent years. It is well known, that the hydrocarbonbased sulfonated aromatic copolymers display lower proton conductivity in comparison to the perfluoro sulfonated polymers, due to poor phase separation between the hydrophilic and hydrophobic domains and the weak acidic nature of SO 3 H group (38).…”

Water Soluble Polymers as Proton Exchange Membranes for Fuel Cells

“…Sulfonated or phosphonated polybenzimidazoles (PBI) [14][15][16], polybenzoxazoles (PBO) [17,18] and polybenzothiazoles (PBT) [19,20] have also been investigated for possible use as PEMs. Nevertheless, there are still unresolved application issues with these membranes due variously to low proton conductivity under low humidity conditions, and poor stability during long-term operation.…”