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SYSO: Symposium Self-organizing Surfaces and Interfaces

SYSO 2: Self-Organizing Surfaces and Interfaces II

SYSO 2.1: Hauptvortrag

Mittwoch, 25. März 2009, 15:45–16:15, BAR SCHÖ

Crystallisation of polymers at surfaces and in thin films — •Günter Reiter — Physikalisches Institut, Universität Freiburg, Deutschland

Crystallisation is one of the most impressive ways of generating order in molecular systems. However, the morphology of crystals can undergo various transitions, driven by different types of instabilities, yielding diverse patterns at hierarchical length-scales. Here, we focus on morphological transitions for polymer single crystals by studying their growth in quasi 2 dimensions, i.e. in thin films with thicknesses in the range of a single crystalline lamella. Our results are compared with theoretical concepts describing morphological instabilities of single crystals which were originally not developed for polymeric systems. Based on these results, we demonstrate that polymer thin films provide valuable model systems for studying general concepts of crystallization. We identify at which point the connectivity of the crystallizing units within chain-like molecules starts to play a measurable role. For example, in contrast to crystals of small molecules, polymer crystals typically have a wide range of melting temperatures, allowing for paradoxical phenomena like the coexistence of melting and crystallisation. Derived from this fact, we demonstrate that a self-seeding technique enables to generate arrays of correlated polymer crystals of uniform size and shape with their orientation inherited from an initial single crystal. We attribute this unique behaviour of polymers to the coexistence of variable fold lengths in meta-stable crystalline lamellae, typical for ordering of complex chain-like molecules.