Properties of Multiblock Sulfonated Poly(arylene ether sulfone)s Synthesized by Precise Controllable Post-sulfonation for Proton Exchange Membranes

A series of multiblock sulfonated poly(arylene ether sulfone)s (SPAES) with various block lengths and predictable ion exchange capacity were synthesized from 4,4′-difluorodiphenyl sulfone, 4,4′-dihydrodiphenyl sulfone and 4,4′-biphenol by one-pot and two-pot polymerization. ¹H-NMR and FTIR spectra confirmed the structure that sulfonic acid groups were introduced precisely on the poly(arylene ether sulfone)s by post-sulfonation which resulted in controllable sulfonation degree. The proton exchange membranes (PEMs)-based SPAES displayed excellent dimensional, thermal, antioxidant stability, proton conductivity and mechanical properties (maximum tensile stress >35 MPa). Thermogravimetric analysis indicated the prepared SPAES began to degrade above 310 °C. The effects of polymerization processes, those were, one-pot hydrophobic segment process, one-pot hydrophilic segment process and two-pot process, on the properties of polymers were investigated. The proton conductivity and microphase separation of SPAES PEMs increased in order of those prepared by one-pot hydrophobic segment process, two-pot process and one-pot hydrophilic segment process. The highest conductivities of SPAES synthesized by the above processes under 80 °C and 100% relative humidity were 213 (MS4), 297 (MB3) and 360 mS·cm⁻¹ (MQ2), respectively.