Herein, we synthesize a coumarin-substituted diacetylene monomer (CODA) and report the novel photo-controlled reversible assembly and disassembly behavior of the polymerized CODA (PCODA) vesicles. The photo-triggered dimerization and cleavage reactions of the coumarin groups within the surface of the adjacent PCODA vesicles can be utilized as the driving force to induce assembly and disassembly of PCODA vesicles. Moreover, the boundary of PCODA vesicles in the aggregates becomes more obscure when the irradiation time exceeds 30 min. Fusion occurs upon close docking of target membranes, driven by sufficient dimerization of the coumarin groups within the surface of PCODA vesicles.