Surface-Induced Interphases During Curing Processes Between Bi- and Pentafunctional Components: Reactive Coarse-Grained Molecular Dynamics Simulations

Abstract

The present reactive molecular dynamics (RMD) simulations discuss the formation of interphase regions in cured polymer adhesives. The latter are obtained from the curing of reactive liquid mixtures composed of pentafunctional linkers and bifunctional monomers in contact with idealized surfaces. The present reactive scheme mimics the one of epoxies with amine linkers, i.e., processes investigated experimentally by Possart and co-workers. Generic RMD simulations are performed in a coarse-grained (CG) resolution to evaluate basic principles in curing characterized by preferential interactions. The creation of linker-rich domains is promoted by preferential surface-linker as well as linker-linker interactions in the reactive mixtures. The dimension of the interphase both in the starting mixture and the cured network depends on these preferential interactions which lead to a retardation of the curing velocity. This retardation behavior is mapped by conversion curves as a function of the number of reactive steps and by the spatially resolved profiles of the connected linkers. Although derived by generic potentials, the simulated reduction of the curing velocity is in agreement with experimental results in epoxies. The chosen interactions also imply a smaller number of linker bonds in the interphase than in the bulk region. The present RMD approach offers insight into key parameters of curing processes under the influence of preferential surface interactions coupled to selective attractions in the liquid starting mixture.

KEYWORDS:

• Adhesion
• Coarse-grained resolution
• Curing between Bi- and pentafunctional components
• Interphase properties
• Reactive molecular dynamics

ACKNOWLEDGMENTS

The present work has been supported generously by the Deutsche Forschungsgemeinschaft (DFG) priority program SPP1369. We are grateful to Hossein Ali Karimi-Varzaneh and Frédéric Leroy for their contributions to earlier stages of the present series of RMD simulations. Thanks to Hossein Eslami for useful comments and to S. Philipp for critically reading the manuscript. Finally, we want to thank Wulff Possart for a number of stimulating discussions initiating the present RMD study.

Notes

One of a Collection of papers honoring Wulff Possart, the recipient in February 2012 of The Adhesion Society Award for Excellence in Adhesion Science, Sponsored by 3M.