The present invention provides materials and methods to enhance dispersion of carbon black within polymer systems, improving both static physical properties and dynamic physical properties of polymers (such as natural or synthetic rubber) containing carbon black. Some variations provide a composition containing a polymer, carbon black, and a performance-enhancing additive comprising amorphous silica, wherein the performance-enhancing additive causes a property improvement associated with or imparted by the carbon black. The performance-enhancing additive scrubs or exfoliates the carbon black in situ, to improve tensile strength, modulus, tear, elongation, dispersion, flow properties, viscosity, hardness, specific gravity, rebound, torque, and/or load of the polymer composite.