Sulfonated Polybenzothiazoles Containing Hexafluoroisopropyl Units for Proton Exchange Membrane Fuel Cells

A sulfonated dicarboxylic monomer containing hexafluoroisopropyl,i.e., 3,3 & PRIME;-disulfonate-2,2-bis(4-carboxyphenyl)hexafluoropropane(SCFA), was prepared via sulfonation and oxidation to synthesize novelsulfonated polybenzothiazoles (sPBT-F) through polycondensation of2,2-bis(4-carboxyphenyl)hexafluoropropane (CFA), SCFA, and 2,5-diamino-1,4-benzenedithioldihydrochloride (DABDT). These sPBT-F series polymers exhibited excellentsolubility due to the incorporation of a flexible hexafluoroisopropylgroup. Meanwhile, the sPBT-F series polymers displayed high thermalstability and were used to prepare tough and soft membranes by solutioncasting. Interestingly, sPBT-F series membranes exhibited excellentwater uptake and low swelling ratio, indicating excellent dimensionalstability. AFM images displayed a region of obvious separation oflight/dark phases, indicating high proton conductivity of sPBT-F seriesmembranes. The sPBT-F82.5 membrane with a high degree of sulfonationdemonstrated a conductivity of 0.14 S cm(-1) at 80 & DEG;C and 100% RH, superior to the results of Nafion 117. Furthermore,the sPBT-F82.5 membrane displayed a maximum power density of 344.33mW cm(-2) and superb durability at a current densityof 0.2 A cm(-2) for 20 h. In summary, the sPBT-F polymersare potential matrix materials for PEMs.

Automated summary

A sulfonated dicarboxylic monomer containing hexafluoroisopropyl was prepared and used to synthesize novel sulfonated polybenzothiazoles. These polymers exhibited excellent solubility and high thermal stability. Membranes made from these polymers showed excellent dimensional stability and proton conductivity, with superior performance to Nafion 117. The sPBT-F82.5 membrane demonstrated a high conductivity of 0.14 S cm(-1) at 80°C and 100% RH, as well as a maximum power density of 344.33 mW cm(-2) and superb durability at a current density of 0.2 A cm(-2) for 20 h. Overall, sPBT-F polymers have great potential as matrix materials for PEMs.