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

Fan, Yanfang, Cornelius, Chris J., Lee, Hae-Seung, McGrath, James E., Zhang, Mingqiang, Moore, Robert, Staiger, Chad L.
Journal of membrane science 2013 v.430 pp. 106-112
activation energy, artificial membranes, carbon dioxide, glass transition temperature, hydrogen, oxygen, permeability, polymers, separation, viscoelasticity
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 Tg's 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.