B03 Substrate-induced molecular order and nucleation in polymer thin films

Friday 1. July 2011
Thurn-Albrecht

It was the aim of the project to work out a fundamental understanding of crystallization induced at the interface between a solid substrate and a liquid polymer. While it was a general experience that crystallization was often induced at interfaces, detailed and microscopic understanding of this process was very limited.
We were able to make the first experimental observation of prefreezing in a molecular system using PE on graphite as a model system. One of the central results  was the experimental confirmation that prefreezing corresponded to a first order wetting transition. The central aim of the project was to further understand the effect of material parameters on prefreezing and to extend our studies to heterogeneous nucleation, the other possible process of interface-induced crystallization. We furthermore planned to compare nucleation in melt based and solution based systems. Suitable model systems had to be identified. Our goal was a direct experimental comparison of prefreezing as an equilibrium process and heterogeneous nucleation as an activated non-equilibrium process. We wanted to understand under which circumstances either of the two processes occurred, how they could be distinguished and which was the practically more relevant pathway. We continued to use the experimental approach developed in the last two funding periods, namely a combination of in-situ AFM-measurements, X-ray scattering experiments in grazing incidence and θ-2 θ-geometry on thin films on well-defined substrates.

Highlighted Publications:
  1. Muhammad Tariq, Oleksandr Dolynchuk, and Thomas Thurn-Albrecht, Independent Variation of Transition Temperature and Prefrozen Layer Thickness at thePrefreezing Transition J. Phys. Chem. C 124, 26184–26192 (2020) 

  2. O. Dolynchuk, M. Tariq, and T. Thurn-Albrecht, Phenomenological Theory of First-Order Prefreezing J. Phys. Chem. Lett. 10, 1942 (2019) 

  3. A.-K. Loehmann, T. Henze, and T. Thurn-Albrecht, Direct Observation of Prefreezing at the Interface Melt-Solid in Polymer Crystallization PNAS 111, 17368 (2014)