Berlin 2001 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 19: Poster: New Methods, Thin Polymer Films, Monolayers

CPP 19.11: Poster

Donnerstag, 5. April 2001, 12:30–15:00, AT1

Surface Reconstruction of a Complex Fluid — •Nicolaus Rehse, Armin Knoll, Robert Magerle, and Georg Krausch — Physikalische Chemie II, Universität Bayreuth, D-95440 Bayreuth

We have studied the thin-film microdomain structure of poly(styrene-b-butadiene-b-methyl-methacrylate) (SBM) and other ABC triblock copolymers with lamellar bulk morphology. In the absence of specific surface interactions one would expect the end blocks to completely cover the surface leading to a homogenous surface. In contrast, after annealing SBM films show two types of terraces exhibiting a 2D packing of PMMA spheres in PS matrix (on terraces of type I) and vice versa (type II). This behaviour can be explained as a surface reconstruction due to frustration of the low-surface-energy middle block. It shows the strong influence of surface energies on the surface structure of the system. This is supported by experiments with different block sequence (BSM) and different surface energies (by exchanging the methyl-methacrylate block by tert-butyl-methacrylate), where this surface reconstruction is not found. Our findings show remarkable similarities with single crystal surfaces. In both cases the ideal surface can be energetically unfavourable leading to surface reconstruction.