In this paper, we study the morphology of diblock copolymers with the body‐centered‐cubic (bcc) phase confined between two flat surfaces. Employing the Landau–Brazovskii mean field theory and the single mode approximation, we obtain three amplitude parameters as functions of temperature, surface field strength, and film thickness. Because of the effect of confinement size and the surface inducement, the morphology of confined diblock copolymers is different from the bulk structure. By controlling confinement size and surface field strength, lamella, undulated lamella, cylinder, and distorted cylinder can be observed in the bcc bulk phase of diblock copolymers. Also, we construct a “phase diagram” of confinement‐induced structures at different surface field strengths. We compare the present theoretical results with the other relevant theoretical results. The predictions about these interesting confinement‐induced structures should be observable in the experiments under suitable conditions.
