Influence of the Graft Length on Nanocomposite Structure and Interfacial Dynamics

Anne Caroline Genix, Vera Bocharova, Bobby Carroll, Philippe Dieudonné-George, Edouard Chauveau, Alexei P. Sokolov, Julian Oberdisse

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4 Scopus citations

Abstract

Both the dispersion state of nanoparticles (NPs) within polymer nanocomposites (PNCs) and the dynamical state of the polymer altered by the presence of the NP/polymer interfaces have a strong impact on the macroscopic properties of PNCs. In particular, mechanical properties are strongly affected by percolation of hard phases, which may be NP networks, dynamically modified polymer regions, or combinations of both. In this article, the impact on dispersion and dynamics of surface modification of the NPs by short monomethoxysilanes with eight carbons in the alkyl part (C8) is studied. As a function of grafting density and particle content, polymer dynamics is followed by broadband dielectric spectroscopy and analyzed by an interfacial layer model, whereas the particle dispersion is investigated by small-angle X-ray scattering and analyzed by reverse Monte Carlo simulations. NP dispersions are found to be destabilized only at the highest grafting. The interfacial layer formalism allows the clear identification of the volume fraction of interfacial polymer, with its characteristic time. The strongest dynamical slow-down in the polymer is found for unmodified NPs, while grafting weakens this effect progressively. The combination of all three techniques enables a unique measurement of the true thickness of the interfacial layer, which is ca. 5 nm. Finally, the comparison between longer (C18) and shorter (C8) grafts provides unprecedented insight into the efficacy and tunability of surface modification. It is shown that C8-grafting allows for a more progressive tuning, which goes beyond a pure mass effect.

Original languageEnglish
Article number748
JournalNanomaterials
Volume13
Issue number4
DOIs
StatePublished - Feb 2023

Funding

This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. A.-C.G. and J.O. are thankful for support by the ANR NANODYN project, Grant ANR-14-CE22-0001-01 of the French Agence Nationale de la Recherche. A.P.S. acknowledges partial support for data analysis and discussions by NSF Polymer program (DMR-1904657).

FundersFunder number
National Science FoundationDMR-1904657
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Division of Materials Sciences and EngineeringANR-14-CE22-0001-01
Agence Nationale de la Recherche

    Keywords

    • SAXS
    • interfacial polymer layer
    • interlayer thickness
    • nanoparticles
    • reverse Monte Carlo
    • segmental dynamics
    • slow-down
    • surface modification

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