Effect on Microdynamics under Repeated Strain of End-Functionalized Chain Additives in Rubber Nanocomposites

Filled rubber nanocomposites exhibit complex mechanical response under repeated strain. After being subjected to repeated loading and unloading cycles, the macroscopic stress-strain behavior changes. Unraveling the mechanisms behind this effect is crucial for improving the mechanical performance of rubber. However, the filler microdynamics that lead to this effect are not yet fully understood. We hypothesize that the softening mechanism in the filled rubber can be altered by modifying the filler/rubber interface. X-ray photon Correlation Spectroscopy (XPCS) measurements provide directionally resolved information about how filler microdynamics change with the modification of the filler/rubber interface using functionalized low molecular weight (LMW) chain additives. The filler network microdynamic response is different when difunctional, end-functionalized linear low molecular weight polymeric additives are added to the rubber than when the end-functionalized additives have a star architecture.