Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 70: Crystallization, Nucleation and Self-Assembly II

CPP 70.5: Vortrag

Donnerstag, 15. März 2018, 16:15–16:30, C 230

Short-polyethylene systems: On the low-temperature states of single chains and few chain aggregates — •Timur Shakirov and Wolfgang Paul — Institute of Physics, University of Halle, Halle, Germany

The phase behavior of polyethylene has been under investigation during many decades. But investigation of single-chain crystallization is a technically difficult problem. One of the reasons for this is that in the case of molecular dynamics simulations as well as in experiments, it is not so easy to distinguish thermodynamic and kinetic effects on chain folding. We here present results of a Wang-Landau type Monte Carlo simulation, which give a possibility to analyze thermodynamic equilibrium properties of a system. Our simulation study of short polyethylene chains is based on a chemically realistic united atom model [1]. Simulation results for deep-energy (or equivalently low temperature) states of single chains of different lengths demonstrate a set of various ground-state configurations: from stretched and hairpin-like configurations of short chains to a helix-like structure reeled round one of the chain's ends. Aggregates of a few chains demonstrate more complex behavior having disordered and ordered phases even for aggregates composed of a couple of chains. Corresponding low-energy configurations differ form configurations of single chains having the same length. However, with increasing chain length, single chain and aggregate morphologies become more similar.

[1] W. Paul, D. Y. Yoon, and G. D. Smith, J. Chem. Phys. 103 (1995) 1702-1709.