This study investigates how bidispersity in star-polymer thin films affects their mechanical properties, specifically toughness and impact resistance. Using molecular dynamics simulations, the researchers model the behavior of thin films composed of bidisperse star polymers with varying arm lengths. They find that, at a fixed molecular weight, high dispersity significantly enhances the toughness and impact resistance of the films without decreasing their elastic modulus. Bidisperse stars with fewer longer arms are less entangled but stretch and interpenetrate for longer times during crazing, leading to increased toughness. These findings highlight controlled dispersity as a design strategy to improve the mechanical properties of polymer composites across Pareto fronts. Polymer thin films are of interest due to their ease of manufacturing and low cost, with favorable properties such as flexibility and lightness. They are used in various applications, including protective coatings, electronics, and food packaging. The tailored mechanical attributes of polymer films are essential for their use in impact-resistant materials. Branched polymers and polymer-grafted nanoparticles (GNPs) have recently attracted attention due to their unique architecture. Star polymers, characterized by a central core with multiple branching arms, are distinguished by their unique topological properties. The study uses nonequilibrium molecular dynamics simulations with the LAMMPS software to examine the effect of dispersity on the mechanical properties of star-polymer thin films. The simulations show that increasing dispersity improves the toughness of the films while keeping the modulus constant. The results also indicate that dispersity enhances the impact resistance of thin films at the late absorption stage while keeping the early absorption energy constant. The findings suggest that dispersity offers considerable potential for improving the design of star-polymer thin films, making a significant step forward in the search for advanced impact-resistant materials. The study highlights the importance of dispersity in enhancing the mechanical properties of polymer composites and provides insights into future research on designing superior materials through defect engineering.This study investigates how bidispersity in star-polymer thin films affects their mechanical properties, specifically toughness and impact resistance. Using molecular dynamics simulations, the researchers model the behavior of thin films composed of bidisperse star polymers with varying arm lengths. They find that, at a fixed molecular weight, high dispersity significantly enhances the toughness and impact resistance of the films without decreasing their elastic modulus. Bidisperse stars with fewer longer arms are less entangled but stretch and interpenetrate for longer times during crazing, leading to increased toughness. These findings highlight controlled dispersity as a design strategy to improve the mechanical properties of polymer composites across Pareto fronts. Polymer thin films are of interest due to their ease of manufacturing and low cost, with favorable properties such as flexibility and lightness. They are used in various applications, including protective coatings, electronics, and food packaging. The tailored mechanical attributes of polymer films are essential for their use in impact-resistant materials. Branched polymers and polymer-grafted nanoparticles (GNPs) have recently attracted attention due to their unique architecture. Star polymers, characterized by a central core with multiple branching arms, are distinguished by their unique topological properties. The study uses nonequilibrium molecular dynamics simulations with the LAMMPS software to examine the effect of dispersity on the mechanical properties of star-polymer thin films. The simulations show that increasing dispersity improves the toughness of the films while keeping the modulus constant. The results also indicate that dispersity enhances the impact resistance of thin films at the late absorption stage while keeping the early absorption energy constant. The findings suggest that dispersity offers considerable potential for improving the design of star-polymer thin films, making a significant step forward in the search for advanced impact-resistant materials. The study highlights the importance of dispersity in enhancing the mechanical properties of polymer composites and provides insights into future research on designing superior materials through defect engineering.