Molecular Dynamics Simulations for the Estimation of the Dielectric Constant of Epoxy‐Amine Networks at Non‐Stoichiometric Ratios

Epoxy‐amine systems form crosslinked thermosets that are widely used as insulating materials. Their wide acceptance partly stems from the fact that, in stoichiometric ratios, fully cured epoxy‐amine systems typically possess high mechanical strength, thermal stability, and good resistance to moisture. However, experiments have revealed that some important mechanical and thermal properties are often improved in off‐stoichiometric epoxy‐amine systems. Correlations of the dielectric constant with stoichiometry and macromolecular structure of these systems have not been explored. We perform molecular dynamics (MD) simulations on well‐equilibrated samples of a particular epoxy‐amine system (Bisphenol A diglycidyl ether/BADGE/DGEBA and Triethylenetetramine/TETA) to understand the consequences of using off‐stoichiometric ratios. Our results show that the key player in modulating the dielectric constant is the network formed by the epoxy and amine. The ability of the network to align with an imposed external electric field depends on the dipole moment of the constituents and the topology of the network they form. The use of off‐stoichiometric ratios provides a means to modulate the dielectric constant by disrupting the perfect network formed at stoichiometry, indicating that other methods of disruption may also be effective in modulating permittivity according to the needs of modern technological innovations.