Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 22: POSTER C

CPP 22.34: Poster

Donnerstag, 27. März 2003, 12:00–14:00, ZEU/250

Surface induced deformations of the mesoscopic microdomain structure in thin films of cylinder forming Block Copolymers — •Armin Knoll, Larisa Tsarkova, Robert Magerle, and Georg Krausch — Physikalische Chemie II, Universität Bayreuth, D-95440 Bayreuth, Germany

We study thin films of polystyrene/polybudatiene block copolymers exhibiting hexagonally ordered polystyrene cylinders in bulk. After annealing, cylinders preferentially align parallel to the film surface. At an incommensurate film thickness, cylinders align perpendicular to the film. In addition, a perforated lamella phase is found in films with a thickness comparable to one cylinder spacing.

With computational image analysis of AFM Tapping Mode (TM) phase images, we analyse in detail the characteristic lattice parameters of the different thin film phases. We find, that the lateral distance of in-plane oriented cylinders increases with increasing number of cylinder layers in the film. The corresponding lattice parameter of the perforated lamella phase is a few percent larger than the spacing of in-plane cylinders. The largest lateral distance between neighboring microdomains is found for upright cylinders. The equilibrium thickness of a layer of cylinders is larger than all lateral lattice parameters.

This indicates, that the unit cell of the cylinders is stretched perpendicular to the film due to surface effects. This in turn leads to a reduced lateral distance of in plane oriented cylinders and eventually to a reconstruction into a perforated lamella phase.