A series of photocrosslinkable multi-block poly(arylene ether sulfone) copolymers containing various block lengths of hydrophilic segments were synthesized. For comparison, a series of random poly(arylene ether) copolymers were also synthesized. The anion exchange membranes(AEMs) were fabricated and in-situ photo-crosslinking was carried out by UV irradiation in a swollen state. The microphase-separated morphologies of the multi-block membranes were characterized by SAXS and TEM experiments, and the membrane properties were investigated by measuring ion exchange capacity (IEC), water uptake, water swelling ratio, ionic conductivity, methanol permeability and alkaline stability. IECs and water uptakes of the crosslinked multi-block membranes were in the range of 1.11-1.42 meq g(-1) and 14.36-31.01% at 20 degrees C, respectively. The hydroxide conductivity was in the range of 11.38-25.00 mS cm(-1) at 20 degrees C, and showed a maximum value of 178.77 mS cm(-1) at 100 degrees C. The multi-block membranes exhibited low methanol permeability (2.75x10(-7) cm(2) s(-1)) at room temperature, which is one order of magnitude lower than that of Nafion (R) 117 (23.8x10(-7) cm(2) s(-1)). The crosslinked membranes showed excellent dimensional stability and alkaline stability with only a slight decrease in ionic conductivity. All the multi-block membranes showed superior properties compared to their corresponding random copolymers.