Title: Collective Nanoparticle Dynamics Associated with Bridging Network Formation in Model Polymer Nanocomposites

Abstract

The addition of nanoparticles (NPs) to polymers is a powerful method to improve the mechanical and other properties of macromolecular materials. Such hybrid polymer–particle systems are also rich in fundamental soft matter physics. Among several factors contributing to mechanical reinforcement, a polymer-mediated NP network is considered to be the most important in polymer nanocomposites (PNCs). Here, we present an integrated experimental–theoretical study of the collective NP dynamics in model PNCs using X-ray photon correlation spectroscopy and microscopic statistical mechanics theory. Silica NPs dispersed in unentangled or entangled poly(2-vinylpyridine) matrices over a range of NP loadings are used. Static collective structure factors of the NP subsystems at temperatures above the bulk glass transition temperature reveal the formation of a network-like microstructure via polymer-mediated bridges at high NP loadings above the percolation threshold. The NP collective relaxation times are up to 3 orders of magnitude longer than the self-diffusion limit of isolated NPs and display a rich dependence with observation wavevector and NP loading. A mode-coupling theory dynamical analysis that incorporates the static polymer-mediated bridging structure and collective motions of NPs is performed. It captures well both the observed scattering wavevector and NP loading dependences of the collective NP dynamics in themore » unentangled polymer matrix, with modest quantitative deviations emerging for the entangled PNC samples. Additionally, we identify an unusual and weak temperature dependence of collective NP dynamics, in qualitative contrast with the mechanical response. Hence, the present study has revealed key aspects of the collective motions of NPs connected by polymer bridges in contact with a viscous adsorbing polymer medium and identifies some outstanding remaining challenges for the theoretical understanding of these complex soft materials.« less

Authors:

Yavitt, Benjamin M.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9308-7472"

Salatto, Daniel ^[1]; Zhou, Yuxing ^[2]; Huang, Zhixing ^[1]; Endoh, Maya K.  ^[1];

• Search DOE PAGES for author "Endoh, Maya K."
• Search DOE PAGES for ORCID "0000-0001-6473-5047"

Wiegart, Lutz  ^[3];

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• Search DOE PAGES for ORCID "0000-0003-4417-8479"

Bocharova, Vera  ^[4];

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• Search DOE PAGES for ORCID "0000-0003-4270-3866"

Ribbe, Alexander E.  ^[5];

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• Search DOE PAGES for ORCID "0000-0002-9924-3429"

Sokolov, Alexei P.  ^[4];

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• Search DOE PAGES for ORCID "0000-0002-8187-9445"

Schweizer, Kenneth S. ^[2]; Koga, Tadanori  ^[1]

• Search DOE PAGES for author "Koga, Tadanori"
• Search DOE PAGES for ORCID "0000-0003-1316-6133"

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+ Show Author Affiliations

1. Stony Brook Univ., NY (United States)
2. Univ. of Illinois, Urbana, IL (United States)
3. Brookhaven National Lab. (BNL), Upton, NY (United States)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
5. Univ. of Massachusetts, Amherst, MA (United States)

Publication Date:

Tue Jun 15 00:00:00 EDT 2021

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division

OSTI Identifier:

1805263

Alternate Identifier(s):

OSTI ID: 1813158

Report Number(s):

BNL-221715-2021-JAAM
Journal ID: ISSN 1936-0851

Grant/Contract Number:  

SC0012704; AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

ACS Nano

Additional Journal Information:

Journal Volume: 15; Journal Issue: 7; Journal ID: ISSN 1936-0851

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; polymer nanocomposites; collective nanoparticle dynamics; polymer bridges; fluid dynamics; diffusion; nanocomposites; chemical structure; polymers