INTERFACE SCIENCE 11, 225–235, 2003 c  2003 Kluwer Academic Publishers. Manufactured in The Netherlands. Hierarchic Structure Formation in Binary and Ternary Polymer Blends MONIKA SPRENGER ∗ AND STEFAN WALHEIM † Fakult¨ at f ¨ ur Physik, Universit¨ at Konstanz, D-78457 Konstanz, Germany ANDRZEJ BUDKOWSKI Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Krak´ ow, Poland ULLRICH STEINER Department of Polymer Chemistry and Materials Science Center, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands u.steiner@chem.rug.nl Abstract. The phase morphology of multi-component polymer blends is governed by the interfacial interactions of its components. We discuss here the domain morphology in thin films of model binary and ternary polymer blends containing polystyrene, poly(methyl metacrylate), and poly(2-vinylpyridine) (PS, PMMA, PVP). When sandwiched between two non-polar surfaces, characteristic lateral phase morphologies are observed after the film formation by spin-coating. We discuss here two techniques, by which hierarchical lateral structures in polymer films can be made. The first method makes use of two simultaneously occurring interfacial instabilities. The second technique employs the effect of a variation of the enthalpic interaction parameters in a ternary polymer mixture on its lateral polymer phase morphology. Keywords: polymer blends, phase separation, polymer films, atomic force microscopy 1. Introduction Commercial polymer based materials are usually com- plex. They consist of a large number of components, which can be other polymers, low molecular weight or- ganic additives, or non-organic fillers. The large num- ber of components are dictated by the desired bulk properties, such as mechanical toughness, thermal ex- pansion, but also by their surface properties, such as adhesion, abrasion, optical appearance, etc. While multi-component mixtures are routinely addressed by the engineering literature, there are fewer studies that consider such systems from a fundamental point of ∗ Present address: Max-Plank Institut f ¨ ur Metallforschung, Heisen- bergstrasse 1, D-70569 Stuttgart, Germany. † Present address: Institut f¨ ur Nanotechnologie, Forschungszen- trum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Germany. view. This is partially due to the rapid increase in com- plexity for each added component, but also because multi-component systems are often considered as an extension of the much studied binary case. As a model system, we considere here mixtures of mutually incompatible polymers [1, 2]. While the in- terplay of demixing and wetting in thin film of weakly incompatible polymer blends is reasonably well under- stood [3], the situation is much less clear in the more common case of strongly incompatible polymers. In most experimental studies, a polymer blend is prepared in the mixed state and demixing is initiated by a temper- ature quench. Since the viscosities of the polymers are high, the change in phase morphology is quasi-static. It is therefore possible to assign a Gibb’s free energy to the blend at each stage during the phase separation process. In the case of strongly incompatible polymers, this approach is no longer possible. Since the critical