Table 2. Ion-Exchange Capacity (IEC), Water Uptake (%), Water Molecule on Functional Group (λ), Bound and Free Water (%), and Dimensional Stability of Different Membranes.

membrane type	IEC (meq/g)	water uptake (%)	λ (SO3/H2O)		dimensional change (%)
Nafion	1.21	11.93	5.48		10.60
SPES	1.4	12.12	4.81	19.54
PAS-1	1.75	17.18	5.45	12.28
PAS-2	2.44	16.54	3.76	9.25
PAS-5	2.47	17.14	3.85		17.15
PAS-10	1.809	17.37	5.33		14.49
PAS-20	2.06	19.87	5.36		8.56