Flow Behavior of Entangled Polymer Nanoparticle Composites in a Nanotube: Insights into Jamming State

H Liu and LJ An and YJ Ruan and YY Lu, MACROMOLECULAR RAPID COMMUNICATIONS, 45 (2024).

DOI: 10.1002/marc.202400019

Using molecular dynamics simulations, this study investigates the equilibrium properties and flow behaviors of entangled polymer nanoparticle composites (PNCs) within a nanotube. The results show that the density distribution of nanoparticles (NPs), displacement of polymer chains and NPs, and the moduli of PNCs remain relatively unaffected when NP volume fractions (phi N) <= 0.10. However, the flow behavior of entangled PNCs deviates from the ideal parabolic profile seen in unentangled PNCs, displaying plug-like flow characteristics with a significant platform region, indicating the presence of shear bands. Interestingly, entangled PNCs at intermediate phi N values undergo a significant alteration in NP distribution under steady flow, resulting in notable NP aggregation. At phi N = 0.30, a distinct change in the static structure of PNCs occurs, reducing the equilibrium distance between neighboring NPs. Consequently, the motion of both polymer chains and NPs becomes restricted, leading to an increase in the moduli of PNCs resembling solid-like behavior. Additionally, the entangled PNCs experience a complete absence of flow, indicating the entry into a jamming state. This study contributes to the understanding of PNCs flow behavior and provides insights into fundamental aspects and practical implications of PNCs. With increasing volume fraction, the distribution of nanoparticles in polymer nanoparticle composites experiences notable changes, resulting in a transition to a jamming state. This transition is associated with distinct rheological properties, including alterations in mean-squared displacement, moduli, and flow field distribution. Understanding these properties is vital for optimizing the flow behavior and processing of polymer nanocomposites across various industrial applications. image

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