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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 4: Crystallization, Nucleation and Self-Assembly I

CPP 4.1: Vortrag

Montag, 17. März 2025, 11:30–11:45, H34

Confined crystallization for studying kinetics and crystal orientation of interface-induced polymer crystallization — •Marthinus van Niekerk, Thomas Thurn-Albrecht, and Oleksandr Dolynchuk — Experimental Polymer Physics, Martin Luther University Halle-Wittenberg, Germany

Understanding interfacial interactions is essential to understanding the mechanisms and kinetics of interface-induced crystallization (IIC), namely heterogeneous nucleation or prefreezing, and resultant material properties. While heterogeneous nucleation is an activated process occurring below T_m, prefreezing is an equilibrium process producing a stable crystalline layer above T_m that thickens upon cooling. Quantifying the influence of interfacial interactions on the kinetics of IIC and crystal morphology has long been elusive and is addressed in this work. We present a systematic study of confined crystallization in micrometer-sized dewetted droplets of poly(є-caprolactone) (PCL) on a range of substrates, allowing numerical analysis of isolated nucleation events and kinetics. Our results show that prefreezing significantly enhances crystallization kinetics compared to nucleation, resulting in simultaneous crystallization of PCL droplets close to T_m. X-ray scattering reveals the preferred crystal orientation in PCL droplets crystallized by IIC, which is strongest for prefreezing and is supported by striking differences in lamellar morphologies observed in AFM. Thus, we present both quantified nucleation kinetics and crystal orientation for different cases of IIC and show that prefreezing enhances crystallization kinetics and anisotropic crystal orientation most effectively.

Keywords: Prefreezing; Heterogeneous nucleation; Crystallization; Interfaces; Substrates