Atomistic simulations of vinyl polymers

Abstract

Vinyl polymers offer the particularity that small modifications in their microscopic structures can lead to drastic effects at the macroscopic level. Full-atomistic simulations are thus genuinely invaluable for probing the results of such variations in backbone architectures, alternations of side chains and so on. However, the link between the microscale and the macroscale is not straightforward, and as a consequence, establishing multi-scale relationships requires great care. In this article, we review our atomistic simulation studies of vinyl polymers by focusing on the approach that we have developed in recent years in order to justify any ensuing analyses and interpretations. We first examine how to achieve mechanical equilibrium and cubic symmetry for the initial amorphous configurations of polymers. The reproducibility of the simulation results and their linear correlations with experimental data are two essential criteria for corroborating the validity of our method. Different vinyl architectures are then explored, and we demonstrate correlations of the simulation outcomes with existing theories. The crystalline contribution was also similarly studied, and the data provided evidence for the appropriateness of our approach. Our methods have validated their power to capture the effects of any local phenomena and their potential consequences in the macroscopic realm of these materials.

Keywords:

• tacticity
• glass transition
• mechanical equilibrium
• amorphous polymers
• crystal polymers

Acknowledgements

The present work was financially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Centre Québécois des Matériaux Fonctionnels (CQMF), the Fonds Québécois de la Recherche sur la Nature et les Technologies (FQRNT) and the Université de Sherbrooke. Computations have been made possible through funds from the Canadian Fund the Innovation (CFI), and Calcul Québec (former Réseau Québécois de Calcul Haute Performance) and Compute Canada. The author gratefully acknowledges the financial support from all these agencies. Moreover, he recognises the special contributions made by past and present students who have worked and are working on the atomistic simulations of polymers in his research group: N. Metatla (Ph.D.,2008); P. Laflamme (M.Sc., 2006, Ph.D., 2012); N. Anousheh (Ph.D.); S. Palato (M.Sc.); A. Plante (M.Sc., 2012). He also acknowledges Prof. S. Lacelle for helpful discussions during the writing of this review.

Notes

^1. The most rapid motion among atoms, i.e. the stretching vibration of the C–H bond, in order of 10¹⁴ s^− 1, must be correctly described. It thus involves an integration step of 10^− 15 s. in the solving of the Newton's equation using the Verlet-Leapfrog algorithm.