Epitaxial Crystallization of Polyethylene via Prefreezing: Effect of Strength of Substrate Interaction

M. Tariq, A. -K. Flieger, and T. Thurn-Albrecht

Institute of Physics, Martin Luther University, Halle-Wittenberg, Germany

The process of crystallization is most often initiated at an interface to a solid surface due to a decreased nucleation barrier. A solid surface can induce crystallization either by heterogeneous nucleation [1] or by prefreezing [2], where these two processes are very different from each other from a thermodynamics point of view. Previously we observed prefreezing occurring in polyethylene on the surface of graphite [2]. In this system a thin crystalline layer is first formed at the solid interface at a temperature 16 K higher than bulk melting temperature and the thickness of this prefreezing layer increases upon approaching melt-solid coexistence. Here we present another case where polyethylene crystallizes via prefreezing on a molybdenum disulfide substrate which has a stronger effect on the crystallization of polyethylene. Using in-situ high temperature AFM measurements we show that the prefreezing layer is stable in a temperature range up to about 47 K above the bulk melting temperature.

[1] R. P. Sear, J. Phys.: Condens Matter, 19, 033101 (2007). (link)
[2] A. –K. Löhman, T. Henze, T. Thurn-Albrecht, Proc Natl Acad Sci, 111, 17368 (2014). (link)