Microscopic Observation of Interface-Induced Crystallization via Prefreezing from Polymers Melts

The microscopic ordering process that a liquid undergoes during crystallization is often initiated at an interface to a solid. Different processes have been suggested by theory to occur at this interface. Of special interest is prefreezing - the formation of a thin crystalline layer at the interface already at temperatures above the melting temperature. Because of the difficult accessibility of the buried interface, experimental proof of crystallization by prefreezing has been elusive in molecular systems. We here present in situ AFM-observations of such a process in two polymeric model systems and show that prefreezing is a first-order prewetting transition. A quantitative description of the phenomena is possible with a phenomenological theory. The results not only contribute to our fundamental understanding of crystallization but might also be useful for the preparation of well-ordered oriented thin films of crystalline organic materials.
References
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Interface-Induced Crystallization of Polycaprolactone on Graphite via First-Order Prewetting of the Crystalline Phase
Macromolecules 51, 189-194 (2018)