AbstractA series of A‐B‐A triblock copolymers consisting of poly(2‐acrylamido‐2‐methylpropanesulfonic acid) as outer blocks and polystyrene as the middle block was synthesized by polymerizing 2‐acrylamido‐2‐methylpropanesulfonic acid at the ends of a diethyldithiocarbamate‐terminated polystyrene, in which the terminal diethyldithiocarbamate groups act as the radical initiator under photo‐irradiation. The heterogeneous character of the block copolymers in solutions is discussed on the basis of the solubility behavior an