The effect of block length upon structure, physical properties, and transport within a series of sulfonated poly(arylene ether sulfone)s

The gas transport and physical properties of sulfonated poly(arylene ether sulfone) was studied as a function of sulfonated and unsulfonated block length (5k:5k, 10k:10k, and 15k:15k). Viscoelastic properties were evaluated using Dynamic Mechanical Analysis (DMA) to observe polymer relaxations and domain compatibility. A decrease in glass transition temperature Tg was observed with increasing block length. 5k:5k had a single Tg (241 °C), while micro-phase separation between 10k:10k and 15k:15k domains create two Tgʹs that are slightly merged (191 °C, 236 °C and 182 °C, 233 °C). Swelling measurements revealed that film dimensional changes were greater in the plane normal to the film than parallel with increasing block size. He, H2, CO2, and O2 permeability decreased with increasing sulfonated block length with no interchain spacing dependence. The apparent activation energy for permeation Ep increased with gas kinetic diameter size and had a maximum value for 15k:15k. A trade-off relationship between sulfonated and unsulfonated polymer block length is linked to phase separation, water swelling, and gas permeability.