REVIEW ON INTERFACIAL INTERACTIONS AND SEGMENTAL MOTION OF FILLED RUBBER COMPOUNDS

Rubber compounds containing soft rubber and hard reinforcing filler have been shown to exhibit superior properties compared with 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 long-standing controversial topic. Therefore, 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. The review begins by describing intermolecular forces and filler-mediated interactions, including the role of filler attributes and rubber–filler interactions, and discussing appropriate methods to investigate segmental mobility. Next, measurements of microscopic details of segmental motion in various rubber compounds reinforced with fillers, such as nanocarbon, silica, and hybrid fillers, are presented, highlighting why and how fillers interact with elastomers and arguing for an urgent need to consider the filler-mediated interactions for better and accurate rubber reinforcement. In addition, 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 the interfacial layer and polymer chain mobility of rubber compounds are discussed.