Water diffusion and dynamic motion within the confined sPEEK channel are examined. To produce materials with different channel dimension, sPEEK/hyper branch mBMI membrane are prepared by insitu polymerization. NMR T1 and T2 relaxation time measurements are employed to understand the dynamic behavior of water at low (λ=2-3) medium (λ=4-8) and high (λ=14-20) water uptake in these membranes. At fully saturated extreme, the activation energy is found to be higher (30 to 40 kJ/mole) than that of the bulk water (20 to 30 kJ/mole). This is due to the fact that water diffusion occurs in the constraint channel, thus experiencing higher viscosity. On the other hand, at low water uptake, the water migration activation energy is lower than that of the bulk or in the fully saturated sample. This suggests the proton motion involves the relay motion of interconnected hydrogen boding network formed between the sulfonated/ amine group of mBMI with the residue water.