Calorimetry on small systems—a thermodynamic contribution

• Published in: Thermochimica acta Vol. 403; no. 1; pp. 25 - 36
• Main Author: Hohne, G W H
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 26.06.2003; Elsevier Science
• Subjects: Applied sciences; Exact sciences and technology; Melting; Organic polymers; Physicochemistry of polymers; Polymer; Properties and characterization; Small crystals; Surface melting; Thermal and thermodynamic properties; Thomson equation; Small crystals; Surface melting; Polymer; Melting; Thomson equation; Thermodynamics; Polyethylene; Crystals
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/S0040-6031(03)00180-1

Another thermodynamic approach to the Gibbs–Thomson equation, starting from an incremental composition of enthalpy and entropy of the chain molecule, is presented. This describes the melting temperature of (lamella) crystals of linear, folded and cyclic alkanes as well as polyethylenes (PEs) of different type with only one set of parameters. The essential variable turns out to be the number of repeat units (r.u.) (“beads”) of the respective molecule, incorporated into the crystallite, rather than the crystallite size. The finding supports the melting being a dynamic process which starts at the surface (interface) of the crystallite. The approach helps to understand the melting behavior of semi-crystalline polymers, it enables the cyclic and normal alkanes to serve as model substances for polymer crystals although their crystals are nearly perfect and large by contrast to the situation in semi-crystalline polymers.