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Gürel U, Keten S, Giuntoli A. Bidispersity Improves the Toughness and Impact Resistance of Star-Polymer Thin Films. ACS Macro Lett 2024; 13:302-307. [PMID: 38373272 PMCID: PMC10956491 DOI: 10.1021/acsmacrolett.3c00671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 02/07/2024] [Accepted: 02/15/2024] [Indexed: 02/21/2024]
Abstract
Branched polymer architectures are used to tune the mechanical properties of impact-resistant thin films through parameters, such as chain length and grafting density. While chain dispersity affects molecular properties, such as interpenetration and entanglements, structure-property relationships accounting for dispersity are challenging to obtain experimentally and are often neglected in computational models. We employ molecular dynamics simulations to model the high-rate tensile elongation and nanoballistic impact of thin films composed of bidisperse star polymers with varying arm lengths. We find that, at fixed molecular weight, high dispersity can significantly enhance the toughness and impact resistance of the films without decreasing their elastic modulus. Bidisperse stars with fewer longer arms are less entangled, but stretch and interpenetrate for longer times during crazing, leading to increased toughness. These findings highlight controlled dispersity as a design strategy to improve the mechanical properties of polymer composites across Pareto fronts.
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Affiliation(s)
- Utku Gürel
- University
of Groningen, Zernike Institute for Advanced Materials, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Sinan Keten
- Department
of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3109, United States
- Department
of Mechanical Engineering, Northwestern
University, 2145 Sheridan Road, Evanston, Illinois 60208-3109, United States
| | - Andrea Giuntoli
- University
of Groningen, Zernike Institute for Advanced Materials, Nijenborgh 4, 9747AG Groningen, The Netherlands
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Cang Y, Sainidou R, Rembert P, Matyjaszewski K, Bockstaller M, Graczykowski B, Fytas G. Architecture Controls Phonon Propagation in All-Solid Brush Colloid Metamaterials. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023:e2304157. [PMID: 37972268 DOI: 10.1002/smll.202304157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 10/27/2023] [Indexed: 11/19/2023]
Abstract
Brillouin light scattering and elastodynamic theory are concurrently used to determine and interpret the hypersonic phonon dispersion relations in brush particle solids as a function of the grafting density with perspectives in optomechanics, heat management, and materials metrology. In the limit of sparse grafting density, the phonon dispersion relations bear similarity to polymer-embedded colloidal assembly structures in which phonon dispersion can be rationalized on the basis of perfect boundary conditions, i.e., isotropic stiffness transitions across the particle interface. In contrast, for dense brush assemblies, more complex dispersion characteristics are observed that imply anisotropic stiffness transition across the particle/polymer interface. This provides direct experimental validation of phonon propagation changes associated with chain conformational transitions in dense particle brush materials. A scaling relation between interface tangential stiffness and crowding of polymer tethers is derived that provides a guideline for chemists to design brush particle materials with tailored phononic dispersion characteristics. The results emphasize the role of interfaces in composite materials systems. Given the fundamental relevance of phonon dispersion to material properties such as thermal transport or mechanical properties, it is also envisioned that the results will spur the development of novel functional hybrid materials.
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Affiliation(s)
- Yu Cang
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Zhangwu Road 100, Shanghai, 200092, China
| | - Rebecca Sainidou
- Laboratoire Ondes et Milieux Complexes UMR CNRS 6294, UNIHAVRE, Normandie University, 75 rue Bellot, Le Havre, F-76600, France
| | - Pascal Rembert
- Laboratoire Ondes et Milieux Complexes UMR CNRS 6294, UNIHAVRE, Normandie University, 75 rue Bellot, Le Havre, F-76600, France
| | - Krzysztof Matyjaszewski
- Chemistry Department, Carnegie Mellon University, 4400 Forbes Avenue, Pittsburgh, PA, 15213, USA
| | - Michael Bockstaller
- Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA, 15213, USA
| | - Bartlomiej Graczykowski
- Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznanskiego 2, Poznan, 61-614, Poland
| | - George Fytas
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
- Institute of Electronic Structure and Laser, FORTH, N. Plastira 100, Heraklion, 70013, Greece
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