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The dynamics of polymer nanocomposites varies depending on the physics and chemistry at the polymer–nanoparticle interface. The physical aging of the nanocomposites is accelerated or retarded based on interfacial interactions and the state of polymer adsorption at the interfaces. In this study, we investigated the aging kinetics of silica–polystyrene nanocomposites using differential scanning calorimetry, focusing on the effect of local conformations of chains adsorbed on the nanofiller surface. The results show that the temperature dependence of the aging rate follows a Vogel–Fulcher–Tammann relationship at high temperatures, whereas it exhibits an Arrhenius-like behavior below a characteristic temperature (Tc). Notably, at T < Tc, the aging rate decreases with increasing loop height of the chains adsorbed on the filler surface, but the activation energy remains unchanged. We proposed that the suppression of the aging rate at T < Tc is likely related to an increase in the length scale over which the slow interfacial dynamics can propagate due to the increased topological interactions between the chain loops of a larger size and the free chains in the matrix. The increased packing frustration occurring at the filler surface occupied by the larger loops might also contribute to the decreased aging rate. [ABSTRACT FROM AUTHOR]

Two challenging scientific disciplines, i.e., the physics of glasses [Anderson, Science 267, 1615 (1995); Kennedy and Norman, Science 309, 75 (2005)] and interface chemistry [Sanders, 125 Questions: Exploration and Discovery (Science/AAAS, 2021); Yates and Campbell, Proc. Natl. Acad. Sci. U. S. A. 108, 911 (2011)], converge in research on the dynamics of glass surfaces. In recent decades, studies have revealed that glasses exhibit profound alterations in their dynamics within nanometers of interfaces. Rather, at the free surfaces of glassy materials with arrested bulk dynamics, a highly mobile ultrathin layer is present, wherein molecular mobility is much faster than in the bulk. Enhanced surface mobility has become an important scientific concept and is intrinsic and universal to various categories of glasses (e.g., molecular, metallic, and polymeric glasses), thus having technological implications for processing and applications of glasses. This review provides a comprehensive summary of the historical evolution of the concept, characterization, theoretical modeling, and unique features of dynamics at the surfaces of glasses. Additionally, this paper also illustrates potential advantages of incorporating this concept into designing improved materials with extraordinary properties. We hope this review article will contribute to the current understanding of the unique surface dynamics of glassy materials. [ABSTRACT FROM AUTHOR]