Direct Structural Evidence for Interfacial Gradients in Asymmetric Polymer Nanocomposite Blends

Anne Caroline Genix; Vera Bocharova; Bobby Carroll; Philippe Dieudonné-George; Michael Sztucki; Ralf Schweins; Alexei P. Sokolov; Julian Oberdisse

doi:10.1021/acsami.1c06971

Direct Structural Evidence for Interfacial Gradients in Asymmetric Polymer Nanocomposite Blends

Anne Caroline Genix, Vera Bocharova, Bobby Carroll, Philippe Dieudonné-George, Michael Sztucki, Ralf Schweins, Alexei P. Sokolov, Julian Oberdisse

Soft Materials and Membranes

Research output: Contribution to journal › Article › peer-review

7 Scopus citations

Abstract

Understanding the complex structure of polymer blends filled with nanoparticles (NPs) is key to design their macroscopic properties. Here, the spatial distribution of hydrogenated (H) and deuterated (D) polymer chains asymmetric in mass is studied by small-angle neutron scattering. Depending on the chain mass, a qualitatively new large-scale organization of poly(vinyl acetate) chains beyond the random-phase approximation is evidenced in nanocomposites with attractive polymer-silica interactions. The silica is found to systematically induce bulk segregation. Only with long H-chains, a strong scattering signature is observed in the q range of the NP size: it is the sign of interfacial isotopic enrichment, that is, of contrasted polymer shells close to the NP surface. A quantitative model describing both the bulk segregation and the interfacial gradient (over ca. 10-20 nm depending on the NP size) is developed, showing that both are of comparable strength. In all cases, NP surfaces trap the polymer blend in a non-equilibrium state, with preferential adsorption around NPs only if the chain length and isotopic preference toward the surface combine their entropic and enthalpic driving forces. This structural evidence for interfacial polymer gradients will open the road for quantitative understanding of the dynamics of many-chain nanocomposite systems.

Original language	English
Pages (from-to)	36262-36274
Number of pages	13
Journal	ACS Applied Materials and Interfaces
Volume	13
Issue number	30
DOIs	https://doi.org/10.1021/acsami.1c06971
State	Published - Aug 4 2021

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. The authors thank the Institut Laue-Langevin (ILL) for supplying beamtime under the proposal number 9-12-505. The low- q SAXS experiments were performed on the beamline ID02 at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. We are grateful to M.S. at the ESRF for providing assistance in using the beamline ID02.

Funders	Funder number
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Division of Materials Sciences and Engineering	ANR-14-CE22-0001-01
Agence Nationale de la Recherche

Keywords

chain-mass asymmetry
concentration fluctuations
interfacial segregation
isotopic polymer blends
low- q upturn
polymer nanocomposites
small-angle scattering

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10.1021/acsami.1c06971

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title = "Direct Structural Evidence for Interfacial Gradients in Asymmetric Polymer Nanocomposite Blends",

abstract = "Understanding the complex structure of polymer blends filled with nanoparticles (NPs) is key to design their macroscopic properties. Here, the spatial distribution of hydrogenated (H) and deuterated (D) polymer chains asymmetric in mass is studied by small-angle neutron scattering. Depending on the chain mass, a qualitatively new large-scale organization of poly(vinyl acetate) chains beyond the random-phase approximation is evidenced in nanocomposites with attractive polymer-silica interactions. The silica is found to systematically induce bulk segregation. Only with long H-chains, a strong scattering signature is observed in the q range of the NP size: it is the sign of interfacial isotopic enrichment, that is, of contrasted polymer shells close to the NP surface. A quantitative model describing both the bulk segregation and the interfacial gradient (over ca. 10-20 nm depending on the NP size) is developed, showing that both are of comparable strength. In all cases, NP surfaces trap the polymer blend in a non-equilibrium state, with preferential adsorption around NPs only if the chain length and isotopic preference toward the surface combine their entropic and enthalpic driving forces. This structural evidence for interfacial polymer gradients will open the road for quantitative understanding of the dynamics of many-chain nanocomposite systems.",

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Direct Structural Evidence for Interfacial Gradients in Asymmetric Polymer Nanocomposite Blends

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