Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Poster: Crystallisation, Nucleation and Self assembly

CPP 17.1: Poster

Tuesday, March 27, 2012, 18:15–20:15, Poster A

Stabilization of crystalline order in thin films of polyethylene close to a graphite substrate — •Ann-Kristin Löhmann, Thomas Henze, and Thomas Thurn-Albrecht — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Germany

The interface between a polymer melt and a crystalline surface plays an important role during crystal nucleation as well as during crystal growth. Thin polymer films on crystalline substrates can be considered as model systems. We present temperature dependent AFM measurements of thin polyethylene (LLDPE) films on graphite. Upon heating to the melting temperature the polymer film dewets leaving behind a thin ordered film of polyethylene showing the same lamellar structure as the semicrystalline film at lower temperatures. This ordered layer at the polymer-substrate interface is a few nanometres thick and stable at temperatures higher than the bulk melting point. For LLDPE-samples the ordered layer could be observed up to a temperature of 122°C, whereas the bulk melting point was 108°C. We speculate that this interfacial layer is responsible for heterogeneous nucleation on graphite and induces crystal growth of polyethylene perpendicular to the surface of the substrate.