Comprehensive Morphology of ABS Latex Particles Revealed through Mathematical Modeling

The structured grafted acrylonitrile–butadiene–styrene (ABS) polymer particles are used as impact modifiers in ABS materials. The density of the styrene–acrylonitrile (SAN) copolymer grafted onto the poly(butadiene) (PB) chains is a crucial characteristic of these particles. It directly influences particle morphology and determines the dispersion efficiency and compatibility of ABS particles in the SAN matrix. The detailed characterization of the morphology of the ABS particles will open the possibility to tune the final properties of the ABS materials. This study presents the development of a mathematical model for the dynamic formation of polymer–polymer structured latex particles guided by the forces determining particle morphology. Detailed information on the distribution of SAN clusters both within the PBD matrix (internal) and on its surface (external) as well as the partial diffusion of the external clusters was obtained. The model was assessed using detailed experimental ABS latex particle morphology characterization using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography on selectively stained latex samples followed by three-dimensional (3D) image reconstruction. The model well predicts the detailed morphology of ABS particles, including the size distribution of internal and surface clusters and the level of partial penetration of the surface SAN clusters revealed through HAADF-STEM tomography.