Irreversible Adsorption in Polymer Nanocomposites Perturbs Local Tg and Dynamics

Irreversible adsorption can occur at a polymer-substrate interface when a polymer is annealed above its Tg—a standard step in the preparation of polymer-based systems. While irreversible adsorption has been demonstrated to significantly perturb local and bulk glassy properties in thin films, detailed investigations have yet to extend to more complex systems such as polymer nanocomposites, where the evolution and consequences of irreversible adsorption remain largely uninterrogated due to limitations imposed by indirect characterization methods. In this study, we demonstrate a novel approach combining stepwise assembly of polymer nanocomposites—that is, sequential preparation of adsorbed and unadsorbed regions—with direct characterization techniques such as transmission electron microscopy and fluorescence spectroscopy. This approach enables direct access to local features and dynamics of irreversibly adsorbed layers within nanocomposites, affording detailed measurements of layer thickness and Tg. Our approach is generalizable to diverse polymer-nanoparticle pairings and can be extended to probe a range of local properties, including governing chain dynamics. The insights provided by this work may inform the design of sophisticated new materials with desirable properties.