Diblock copolymer films: free-energy analysis

The formation of the lamellar pattern in thin films of even diblock copolymers confined by hard walls is studied. The analysis of the free energy of a film with lamellae parallel to the confining walls, in the weak segregation regime, indicates that, for a given molecular size, the number of lamellae formed is fixed. The transition from a state from n to n+1 lamellae, as the film thickness is increased, is discontinous and there is a range of values of film thickness where the formation of parallel lamellae is disfavorable.