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Relative effects of polymer composition and sample preparation on glass dynamics

Published

Author(s)

Christopher Soles, Amanda L. Forster, Katherine Evans, Madhusudan (Madhu) Tyagi, Robert M. Elder, Timothy Sirk, Joseph Dennis, Kanae Ito, Osama Yamamuro, Hiroshi Akiba

Abstract

Modern design of common adhesives, composites and polymeric parts makes use of polymer glasses that are stiff enough to maintain their shape under a high stress while still maintaining a ductile behavior after the yield point. Typically, material compositions are tuned with co-monomers, polymer blends, plasticizers, or other additives to arrive at a tradeoff between the elastic modulus and toughness. In contrast, strong changes to the mechanics of a glass are possible by changing only the molecular packing during vitrification or even deep in the glassy state. For example, photoplasticization in deeply glassy polymers has been shown to alter the glass temperature and unpack the local glass environment near responsive groups . Conversely, physical aging or processing techniques such as physical vapor deposition increase the density, embrittle the material, and increase elastic modulus. Here, we use molecular simulations, validated by positron annihilation lifetime spectroscopy and quasi-elastic neutron scattering, to analyze the free volume distribution and the resulting dynamics of glassy co-polymers where the composition is systemically varied between polar NBOH and non-polar ENB monomers. The dynamics of these glasses, quantified by the Debye-Waller factor, are compared with softer, lower density states that have potential for faster structural relaxations and improved ductility.
Citation
Soft Matter

Keywords

polymers, molecular dynamics, simulations, modeling, neutron scattering, positron annihilation, mechanical properties, impact strength, toughness

Citation

Soles, C. , Forster, A. , Evans, K. , Tyagi, M. , Elder, R. , Sirk, T. , Dennis, J. , Ito, K. , Yamamuro, O. and Akiba, H. (2022), Relative effects of polymer composition and sample preparation on glass dynamics, Soft Matter, [online], https://doi.org/10.1039/d2sm00698g, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934832 (Accessed May 23, 2024)

Issues

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Created August 17, 2022, Updated January 24, 2023