Butterfly Patterns for Stretched Inhomogeneous Gel Networks Using Large-Scale Molecular Dynamics Simulations

Large-scale coarse-grained molecular dynamics simulations of inhomogeneous gel networks were performed to investigate abnormal butterfly patterns in 2D scattering patterns. The networks were diamond lattice-based with distributions in the number of beads between the cross-link points. Remarkably, the results confirm that the abnormal butterfly pattern originates from a stronger inhomogeneity. For the examined systems, the range of scattering wavevector q for the normal butterfly pattern was markedly different from those for the abnormal butterfly patterns. The findings address an essential aspect of the discrepancy between the theoretical prediction and experimental observations. We also confirmed that the peak position q_x* and intensity of the abnormal butterfly pattern decreases and increases, respectively, with increasing stretching ratio λ. As increasing inhomogeneity, it was found that the lower threshold of λ for the region where q_x* and λ have a linear relationship decreased and the peak intensity increased. This analytical approach to the abnormal butterfly pattern allows us to study the difference in network properties of gel networks for different random cross-linking conditions.