Insights into multi-scale structural evolution and dielectric response of poly(methyl acrylate) under pre-strain: A simulation study

The structural evolution of dielectric elastomer induced by pre-strain is a complex, multi-scale process that poses a significant challenge to a deep understanding of the effect of pre-strain. Through simulation results, we identify the variation in the dielectric constant and multi-scale (electronic structure, molecular chain conformation, and aggregation structure) response of poly(methyl acrylate). As the pre-strain increases, the dielectric constant initially rises (below 200% pre-strain) and then declines (above 200% pre-strain). Analysis of the charge distribution, surface electrostatic potential, HOMO–LUMO bandgap, and electron density differences reveal that adjusting chain conformation appropriately could enhance polarity domain and electron polarization. The correlation between permittivity and segment dynamics of deformed molecules is explored, encompassing segment orientation, mean shift displacement, and diffusion coefficient. Following molecular chain orientation, the kinematic capability of the chain segment improves, which leads to an increase in the number and activity of effective dipoles and the enhancement of orientation polarization. Excessive stretching restricts the polymer molecular chain mechanically, reducing the number and activity of effective dipoles and negatively impacting electron polarization. The permittivity transitions from isotropic to anisotropic behavior when the system is subjected to strain. This study provides an interesting solution for research on multiscale responses and intrinsic mechanisms of pre-strain.