Radiation grafted and sulphonated PEEK (poly ether ether ketone) membranes have been analyzed for water management within the matrix. Grafting is done using alpha methyl styrene-butyl acrylate (AMS/BA) mixture. Membranes exhibit enhanced water content with the increasing ionic content due to higher hydrophilicity. However, the water/ionic site ratio increases significantly with the increasing graft levels. The ionic mobility also increases with increasing graft levels. It is stated that the water management within the hydrophilic membrane matrix plays a key role and is responsible for the high proton mobility at higher graft levels in the membrane. This, in turn, is governed by the physiochemical changes taking place in membranes due to the grafting and sulfonation process. A correlation of the higher water/ionic site ratio arising out of the structural changes in the proton exchange membranes may be developed by radiation grafting of AMS/BA followed by sulfonation.