Structures and dynamics of polymer nanocomposites: filler-polymer interaction and desorption-mediated agglomeration

Abstract

The delicate balance between filler-filler and filler-polymer interactions primarily determines the thermodynamics governing nanofiller dispersion in polymer matrices. While it is well established that the relative strength of these interactions significantly influences dispersion quality, a critical gap remains in our understanding of how dynamic changes in these interactions affect multiscale structures and material properties. In this work, we employ polymer matrices and fillers with varying polarities to elucidate the influence of interfacial energy on filler dispersion and mechanical reinforcement. A detailed analysis of the hierarchical filler structures demonstrates that enhanced attractive filler-polymer interactions promote nanofiller dispersion. Notably, particles with lower surface hydroxyl density impose stronger topological constraints on the polymer matrix, thereby producing a greater enhancement of the rubbery modulus at the same specific area. This phenomenon can be attributed to the distinct loop conformation of adsorbed polymer chains according to the adsorption-induced entanglement mechanism. Through quantitative analysis of the failure of time-temperature superposition, we uncover temperature-dependent variations in the adsorption state, which are further corroborated by thermodynamic analysis of desorption using Fourier transform infrared spectroscopy. Our results reveal that interfacial adhesion energy and the conformational state of adsorbed chains govern the desorption process. Desorption of chains exhibiting loop conformations triggers further nanofiller agglomeration.