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PO: Polymerphysik
PO 6: Poster: Dünne Filme und Grenzfl
ächen
PO 6.11: Poster
Tuesday, March 2, 1999, 14:00–16:00, Foyer
Structure of diblock copolymers close to the surface — •D. W. Schubert1, M. Pannek1, and M. Stamm2 — 1GKSS Research Centre, Max - Planck - Strasse, D-21502 Geesthacht (Germany) — 2Max-Planck-Institut f"ur Polymerforschung, Ackermannweg 10, D-55128 Mainz (Germany)
This work is focused on the lamellar morphology of symmetrically diblock copolymers in the ordered and disordered state. A lamellar structure can be formed in the vicinity of an interface also in the bulk disordered state, due to a difference of surface energies of the block materials. Utilizing thin film samples of a spin coated and annealed P(S(D)-block-nBMA) (Mw = 72 kg/mol) diblock copolymer this effect could be investigated by neutron reflectometry (NR). The NR study reveals a damped cosine modulation of the composition in the z direction, perpendicular to the film surface. Accurate values for the periodicity L and decay length ξ are accessible. Utilizing the theory of Fredrickson, L and ξ can be used to calculate the corresponding value of χN =9.8. This value is indicative of a bulk disordered state which is nearly reached in the middle of the film. Additionally, NR experiments were carried out utilizing approximately twice and three times larger molecular weight samples. Samples are thus in the ordered state. The presented studies reveal new details concerning block copolymers in the intermediate segregation regime and are discussed with respect to interface width and periodicity.