Microphase separation transition and ordering kinetics in thin films of diblock copolymers

Using x-ray reflectivity measurements, we have investigated the structure of films of a symmetric diblock copolymer of polystyrene-b-polyisoprene (M _w =15700). The film thickness is in the range of 1 m. In equilibrium the films consist of lamellae with a thickness of 15.3 nm. They are nearly completely oriented parallel to the substrate. The evolution of oriented structure is studied by time-dependent experiments. The time constants of the structure formation depend strongly on the annealing temperature. An enhancement of the diffuse intensity in the range of Yoneda scattering is evidence for an additional surface structure.