Apparent interactions, cross-linking induced ordering, and cross-link repulsion in model (co-)networks as revealed by scattering data

Based on computer simulations, we analyze how different forms of labeling the network components allows to extract complementary structural information. The analysis relies upon simulations of hetero-complementary bound four-functional star polymers A{}₄ and B{}₄. For optimized contrast between A and B stars, the calculated dynamic scattering intensity resembles A-B block copolymers with an apparent repulsion between both components, accounting for ordering effects due to the complementary coupling scheme. The position of the observed scattering peak is compatible with the radius of gyration of A-B chains connecting adjacent star centers. Labeling the star centers or small regions around them reveals a correlation hole of the star centers and their mutual repulsion, compatible with a Gaussian core repulsion. Accordingly, scattering is suppressed towards small wave vectors, allowing for a decomposition of the observed scattering intensity into a product of the form factor of the labeled star sections and a structure factor describing the distribution of cross-links in space. When choosing opposite scattering amplitudes for the central regions of A and B stars, static scattering directly reveals the distance between connected star centers.