Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 14: Crystallization, Nucleation and Self Assembly I

CPP 14.6: Talk

Tuesday, March 12, 2013, 10:45–11:00, H39

Heterogeneous Nucleation in Epitaxially Crystallized Polyethylene on Graphite — •Ann-Kristin Löhmann, Thomas Henze, and Thomas Thurn-Albrecht — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Germany

We investigate the interface between a polymer melt and a crystalline substrate to get a more microscopic understanding of heterogeneous nucleation.

As a model system we studied crystallization and melting in thin epitaxially crystallized LLDPE films on graphite by high temperature AFM measurements. Upon heating above the melting temperature the polymer film starts to dewet and leaves a thin (only few nanometres) ordered film of polyethylene with a temperature dependent thickness behind. This ordered layer at the polymer-substrate interface shows the same lamellar structure as the semicrystalline film at lower temperatures. The thickness of the ordered layer and as a consequence the dewetting of molten polymer is reversible. The temperature dependence of the stabilized layer can be described by a phenomenological thermodynamic theory [1].

In this epitaxial system a stabilized ordered layer completely wets the substrate at temperatures above the bulk melting point and acts as a nucleus for crystallization, thus explaining the unusual lamellar structure of the crystalline film observable at room temperature.

[1] M. Heni and H. Löwen, Phys. Rev. Lett. 85, 3668-3671 (2000)