Microscopic studies on remarkable rheological behavior of single-chain nanoparticles and linear polymer blends

Abstract

The incorporation of nanoparticles into linear polymers can significantly alter the rheological properties of the system. Nevertheless, the fundamental mechanisms behind this phenomenon have remained elusive. In present study, the changes in the microstructure, particularly the mesh size (ξ) and relaxation time (τ_d) of entangled chains, in a fully polymer/single chain nanoparticles (SCNPs) nanocomposite (PNC) composed of linear polymethyl methacrylate (PMMA) chains and PMMA SCNPs was investigated by microrheological techniques. This research aims to elucidate the mechanism by which soft nanofillers affects the macroscopic properties of SCNP and linear polymer composite systems from a microstructural perspective. Results reveal that SCNPs demonstrate rapid chain segment relaxation and exhibit low viscosity in solution due to three-dimensional spherical structure. More importantly, the addition of SCNPs to the linear matrix significantly modifies the entanglement behavior of the linear polymer, decreasing the entanglement density (lager mesh size), resulting in a lower viscosity, and quicker relaxation times for the system. Additionally, it is observed that the dispersed nature and high penetrability of SCNPs lead to increased disorder in their conformation in solution as their size grows, which gradually diminishes their impact on the entanglement behavior of the system’s chains. Consequently, the effect of SCNPs on the rheological behavior of the system shows a strong dependence on size.