A quantum-based approach to predict primary radiation damage in polymeric networks

Exposing materials to ionizing radiation is a reliable means of sterilization and is a common approach taken in accelerated aging experiments. Initial atomistic-level radiation damage in chemically reactive materials such as silicones is thought to induce a sequence of network-altering events that lead to undesirable macroscale degradation, including permanent set and mechanical failure. We develop a multiscale approach based on semiempirical quantum molecular dynamics (QMD) to predict and analyze primary radiation damage in polydimethylsiloxane (PDMS). Large ensembles of QMD simulations are used to predict the initial reaction cascades that follow from primary knock-on atom radiation events. A graph-based analysis is developed to automatically identify changes to the backbone structure and quantify mechanically relevant network alterations including formation of junction points and chain scissions. Distinguishing characteristics of radiation coupling to different parts of the PDMS backbone are explored.