Document Type
Article
Abstract
Brillouin light spectroscopy is used to measure the elastic moduli of spherical polymer-grafted nanoparticle (GNP) melts as a function of chain length at fixed grafting density (0.47 chains/nm2) and nanoparticle radius (8 nm). While the moduli follow a rule of mixtures (Wood’s law) for long chains, they display enhanced elasticity and anomalous dissipation for graft chains <100 kDa. GNP melts with long polymers at high 𝜎 have a dry zone near the GNP core, surrounded by a region where the grafts can interpenetrate with chain fragments from adjacent GNPs. We propose that the departures from Wood’s law for short chains are due to the effectively larger silica volume fraction in the region where sound propagates—this is caused by the short, interpenetrated chain fragments being pushed out of the way. We thus conclude that transport mechanisms (of gas, ions, sound, thermal phonons) in GNP melts are radically different if interpenetrated chain segments can be “pushed out of the way” or not. This provides a facile new means for manipulating the properties of these materials.
Digital Object Identifier (DOI)
Publication Info
Published in Physical Review Letters, Volume 128, 2022, pages 187801-.
Rights
©Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
APA Citation
Jhalaria, M., Cang, Y., Huang, Y., Benicewicz, B., Kumar, S. K., & Fytas, G. (2022). Unusual High-Frequency Mechanical Properties of Polymer-Grafted Nanoparticle Melts. Physical Review Letters, 128(18). https://doi.org/10.1103/PhysRevLett.128.187801