Interphases in polymer nanocomposites - recent insights from NMR studies
Invited
Abstract
The outstanding performance of modern elastomers is dominated by reinforcement arising from nanometric fillers. The compounds’ peculiar thermo-mechanical properties cannot be explained without consideration of an interphase, i.e., a region of polymer with modified properties [1]. Our, and many others’, work supports a consensus picture of adsorbed components with locally increased Tg, reaching the bulk value over a gradient zone of a few nm [1-3]. This talk focuses on more recent results, mostly obtained by proton low-resolution NMR, that challenge the generality of this picture.
First, we present a more detailed investigation of a specific system, poly(ethylene oxide) – silica, which only superficially follows the above rationale [4]. While we do find rigid components forming a layer of up to 2 nm thickness around the particles, the layer thickness is not a function of temperature, and the chains in this layer feature rather fast, possibly uniaxial dynamics [5]. Moreover, small particles with diameters down to 10 nm exhibit much reduced layer thickness that depends on the end groups [5]. For a more complete picture, we have extended this study to a wider range of particle sizes, polymer molecular weight, and preparation conditions.
Second, spin-diffusion NMR experiments, which probe the size of nanometric domains with distinct mobility, indicate that the smooth-mobility-gradient picture of the “glassy layer” must be replaced by a scenario ruled by dynamic heterogeneities associated with the increased glass transition. We find intriguing similarities of filler-related species and interphase components in semicrystalline polymers and block copolymers [6].
[1] A. Mujtaba et al., ACS Macro Lett. 2014, 3, 481
[2] A. Papon et al., Macromolecules 2011, 44, 913
[3] A. Papon et al., Phys. Rev. Lett. 2012, 108, 065702
[4] S. Y. Kim et al., Macromolecules 2012, 45, 4225
[5] Y. Golitsyn et al., J. Chem. Phys. 2017, 146, 203303
[6] H. Schneider et al., Macromolecules 2017, 50, 8598
First, we present a more detailed investigation of a specific system, poly(ethylene oxide) – silica, which only superficially follows the above rationale [4]. While we do find rigid components forming a layer of up to 2 nm thickness around the particles, the layer thickness is not a function of temperature, and the chains in this layer feature rather fast, possibly uniaxial dynamics [5]. Moreover, small particles with diameters down to 10 nm exhibit much reduced layer thickness that depends on the end groups [5]. For a more complete picture, we have extended this study to a wider range of particle sizes, polymer molecular weight, and preparation conditions.
Second, spin-diffusion NMR experiments, which probe the size of nanometric domains with distinct mobility, indicate that the smooth-mobility-gradient picture of the “glassy layer” must be replaced by a scenario ruled by dynamic heterogeneities associated with the increased glass transition. We find intriguing similarities of filler-related species and interphase components in semicrystalline polymers and block copolymers [6].
[1] A. Mujtaba et al., ACS Macro Lett. 2014, 3, 481
[2] A. Papon et al., Macromolecules 2011, 44, 913
[3] A. Papon et al., Phys. Rev. Lett. 2012, 108, 065702
[4] S. Y. Kim et al., Macromolecules 2012, 45, 4225
[5] Y. Golitsyn et al., J. Chem. Phys. 2017, 146, 203303
[6] H. Schneider et al., Macromolecules 2017, 50, 8598
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Presenters
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Kay Saalwaechter
University of Halle-Wittenberg, Martin-Luther University Halle-Wittenberg
Authors
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Sol Mi Oh
UNIST, Ulsan, South Korea, Ulsan National Institute of Science and Technology
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Mozhdeh Abbasi
University of Halle-Wittenberg, Martin-Luther University Halle-Wittenberg
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So Youn Kim
Ulsan National Institute of Science and Technology, UNIST, Ulsan, South Korea
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Matthias Roos
MIT, Cambridge, MA, USA
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Horst Schneider
University of Halle-Wittenberg
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Kay Saalwaechter
University of Halle-Wittenberg, Martin-Luther University Halle-Wittenberg