Competitive Adsorption in Polymer Nanocomposites: The Molecular Weight and End-Group Effect Revealed by SANS and MD Simulations.

Understanding polymer adsorption at interfaces is essential for designing advanced polymer-based nanomaterials with tailored interfacial properties. Although adsorption significantly influences the macroscopic properties of polymer composites and thin films, a comprehensive understanding of molecular weight (MW)-dependent adsorption remains challenging and controversial, particularly in polydisperse polymer systems, due to the limitations of experimental approaches. Here, we investigate competitive adsorption in bidisperse poly(ethylene glycol) (PEG) melts and demonstrate that shorter chains preferentially adsorb onto nanoparticle surfaces. Combined experiments and molecular dynamics simulations reveal that the high density of terminal hydroxyl groups in short PEG chains strengthens hydrogen bonding at the interface, thereby inducing enthalpy-driven adsorption despite identical polymer backbones. This results in a densely packed interfacial layer that alters the conformation of longer chains. These findings highlight the critical role of end-group functionality in interfacial polymer behavior and provide new insights for tailoring nanocomposite properties.