Simulations on the Thermal Decomposition of a Poly(dimethylsiloxane) Polymer Using the ReaxFF Reactive Force Field
- 20 April 2005
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 127 (19), 7192-7202
- https://doi.org/10.1021/ja050980t
Abstract
To investigate the failure of the poly(dimethylsiloxane) polymer (PDMS) at high temperatures and pressures and in the presence of various additives, we have expanded the ReaxFF reactive force field to describe carbon−silicon systems. From molecular dynamics (MD) simulations using ReaxFF we find initial thermal decomposition products of PDMS to be CH3 radical and the associated polymer radical, indicating that decomposition and subsequent cross-linking of the polymer is initiated by Si−C bond cleavage, in agreement with experimental observations. Secondary reactions involving these CH3 radicals lead primarily to formation of methane. We studied temperature and pressure dependence of PDMS decomposition by following the rate of production of methane in the ReaxFF MD simulations. We tracked the temperature dependency of the methane production to extract Arrhenius parameters for the failure modes of PDMS. Furthermore, we found that at increased pressures the rate of PDMS decomposition drops considerably, leading to the formation of fewer CH3 radicals and methane molecules. Finally, we studied the influence of various additives on PDMS stability. We found that the addition of water or a SiO2 slab has no direct effect on the short-term stability of PDMS, but addition of reactive species such as ozone leads to significantly lower PDMS decomposition temperature. The addition of nitrogen monoxide does not significantly alter the degradation temperature but does retard the initial production of methane and C2 hydrocarbons until the nitrogen monoxide is depleted. These results, and their good agreement with available experimental data, demonstrate that ReaxFF provides a useful computational tool for studying the chemical stability of polymers.Keywords
This publication has 28 references indexed in Scilit:
- Adhesion and nonwetting-wetting transition in theinterfacePhysical Review B, 2004
- ReaxFFSiO Reactive Force Field for Silicon and Silicon Oxide SystemsThe Journal of Physical Chemistry A, 2003
- Mechanism of the Acid-Catalyzed Si−O Bond Cleavage in Siloxanes and Siloxanols. A Theoretical StudyOrganometallics, 2002
- Thermal polydimethylsiloxane degradation. Part 2. The degradation mechanismsPolymer, 2001
- Polydimethylsiloxane thermal degradation Part 1. Kinetic aspectsPolymer, 2001
- The conformation of poly(dimethylsiloxane) in the crystalline statePolymer, 2000
- Empirical potential for hydrocarbons for use in simulating the chemical vapor deposition of diamond filmsPhysical Review B, 1990
- Development of the Colle-Salvetti correlation-energy formula into a functional of the electron densityPhysical Review B, 1988
- Efficient diffuse function‐augmented basis sets for anion calculations. III. The 3‐21+G basis set for first‐row elements, Li–FJournal of Computational Chemistry, 1983
- Special points for Brillouin-zone integrationsPhysical Review B, 1976