The Role of Entanglements for Polymer Crystallization

We use a coarse-grained polymer model to study the crystallization and melting behavior of long polymer chains in the dense state under various conditions. Our primary goal was to investigate the impact of the local state of entanglement on the properties of the lamellar crystal, in particular on the thickness selection, using algorithms to calculate the primitive path of the chains. In situ analysis of the local entanglement length prior to crystallization and analysis of the stem length and crystallinity at the same location reveals a direct correlation between the entanglement length and crystallization properties in the nucleation-controlled regime [1]. We have investigated various scenarios to change the apparent entanglement length in the system such as rapid cooling and cold-crystallization protocols, dilution of the melt by short chains, and the influence of solid substrates [2-4]. All studies confirm the correlation between entanglement length and thickness selection in the dense state. First results on non-concatenated ring polymer melts display an increase of the lamellar thickness and in the degree of crystallization as compared to otherwise identical linear counterparts subject to the same thermal history [5]. Our studies suggest a topological viewpoint on thickness selection in polymer crystals.

References
[1] C.-F. Luo and J.-U. Sommer; Physical Review Letters 112, 195701 (2014).
[2] C.-F. Luo, M. Kröger and J.-U. Sommer; Polymer 109, 71 (2017)
[3] C.-F. Luo, M. Kröger and J.-U. Sommer: Macromolecules 49, 9017 (2016)
[4] C.-F. Luo and J.-U. Sommer; ACS Macro Letters 5, 30 (2016)
[5] H.-Y. Xiao, C.-F. Luo, D. Yan and J.-U. Sommer, manuscript (2017)