Block copolymers with push–pull azobenzene pendants were synthesized by ring-opening metathesis polymerization, and could self-assemble into core–shell nanostructures with high dipolar and interfacial polarizations, which were contributed by the strong polarity of azobenzene pendants bearing both electron-donating pyrrolidine and electron-withdrawing trifluoromethyl or nitro groups, and by the unique nanostructure of polymers, respectively. A block copolymer exhibited a high dielectric constant of 19.1 and a low dielectric loss of 0.01–0.02 at 10²–10⁶ Hz, and a high energy density of 5.54 J cm⁻³ at an electric field of 240 MV m⁻¹ with an energy conversion efficiency of 82.1%. Additionally, the dielectric constant of polymers could be regulated by photoisomerization of azobenzene groups. Besides, polymers displayed an excellent thermal stability with a high thermal degradation temperature of above 300 °C and a high glass-transition temperature of over 200 °C. Therefore, polymers have promising applications in dielectric and electrical energy storage materials.