Abstract

Rubber compounds containing soft rubber and hard reinforcing filler have been shown to exhibit superior properties compared to the neat rubber. Invariably, the macroscopic properties of such nanocomposites are controlled by the interfacial layer formed between the matrix and the filler. Because the interactions within these compounds are complex, unravelling the underlying factors affecting strong intrinsic heterogeneity in the interfacial region is still a controversial topic of long standing. In view of this, a comprehensive survey is presented herein to report the latest experimental, simulation, and theoretical results that characterize interface structure and probe polymer chain mobility in these materials. First, the present review article describes intermolecular forces, filler-mediated interactions including the role of filler attributes and rubber-filler interaction, and appropriate methods to investigate segmental mobility. Then, measurements of microscopic details of segmental motion in various rubber compounds reinforced with fillers, such as nanocarbon, silica, and hybrid fillers are presented. It highlights why and how fillers interact with elastomers, arguing for an urgent need to take into account the filler-mediated interactions for better and accurate rubber reinforcement. Furthermore, the latest studies regarding bound rubber and wet-mixed compounds are discussed. Quantitative correlation of microscopic interactions and macroscopic properties is also provided. Finally, several open challenges in probing interfacial layer and polymer chain mobility of rubber compounds are remarked.