Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: Crystallization and Self Assembly II

CPP 9.6: Talk

Monday, March 22, 2010, 15:15–15:30, H48

What controls heterogeneous nucleation of polymers at interfaces? — •Thomas Henze, Klaus Schröter, and Thomas Thurn-Albrecht — Martin-Luther-University Halle-Wittenberg, Institute of physics, D-06199 Halle (Saale), Germany

We here present a study of the morphology of thin films of polyethylene crystallized from melt on a number of substrates with different ability to invoke crystallization, namely mica, NaCl, SiO₂ and HOPG. Using intermittent-contact mode AFM very different structures are observed on the surface of the polymer films depending on the kind of substrate, the film thickness as well as the degree of branching of the polymer.

For very thin films (about 30 nm) on NaCl and HOPG short, edge-on lamellae oriented according to the symmetry of the underlying crystal lattice show up indicating epitaxial growth. With increasing film thickness (up to 300 nm) the preferred edge-on orientation of the lamellae remains, while the in-plane orientation tends towards one fixed direction. The morphology itself indicates a very high nucleation ability for these kind of substrates. In contrast to that on SiO₂ and mica a spherulitic structure is present showing a preferred flat-on orientation of the lamellae in the thinnest films. However, a quantitative analysis of nucleation density shows that also on these substrates heterogeneous, but non-epitaxial nucleation takes place.