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Abstract The core of this research is separated into three domains, the ultrahigh strain rate response of elastomeric polymers, laser‐induced shock waves , and terahertz time‐domain spectroscopy (THz‐TDS). Elastomers, e.g., polyurea, constitute an advance class of materials suitable for many applications, specifically in high impact loading scenarios, thus, a laser‐induced shock wave (LSW) experimental technique is used to investigate the mechanical response of shock‐loaded polyurea. LSW can submit samples to a strain rate exceeding 106s−1at low strains, enabling determination of material intrinsic failure modes. The large deformation induced during shock loading may alter the macromolecule structure, which can only be detected spectroscopically. Therefore, this research incorporated terahertz bulk spectroscopy to detect and report molecular conformational changes. Microscopy techniques were also used to elucidate changes in the microscale properties, morphology, and topography. The interpretation of the results explicated brittle failure in terms of partial and total spallation and, remarkably, ductile failure leading to plastic deformation, including plastic bulging and adiabatic shearing, not previously associated with LSW technique. Furthermore, spectral changes found in the terahertz regime substantiated the validity of terahertz spectroscopy in elucidating the underlying mechanism associated with the impact mitigating properties of dynamically loaded polyurea.
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Light‐Matter Interactions Revealing Load‐Induced Phase Mobility in Elastomers
Abstract Elastomers with segmental microstructure are a fascinating class of shock‐tolerant and impact‐resistant materials. However, their technological potential remains untapped due to a vague understanding of the molecular contributions to their superior mechanical behavior. Herein, in situ light‐matter interactions, to reveal the extent of microstructural mobility by temporally exploiting molecular processes during creep response, are leveraged. The segmental microstructure comprises aromatic hard domains embedded within an aliphatic soft matrix. High‐resolution digital image correlation reveals the development of strain striations, mild anisotropy, and the mechanisms responsible for domain mobility, where the rate of hard segment mobility is found to be 60% slower than that of the soft segment. Terahertz spectral analyses pinpoint the contributions of interchain hydrogen bonding of the hard segments and their significant conformational changes by observing spectral features at ≈1.2THz and ≈1.67THz. Moreover, the domain mobility is examined using experimental and computational light scattering approaches, uncovering dynamic scattering and elucidating the difference in the complex refractive index of the soft and hard segments. The study unlocks the pathway for quantitative measurements of elusive molecular mobility and conformational changes during mechanical loading and sheds light on the origin of the shock tolerance in some elastomeric polymers with segmental microstructure.
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- Award ID(s):
- 1925539
- PAR ID:
- 10405551
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Macromolecular Rapid Communications
- Volume:
- 44
- Issue:
- 7
- ISSN:
- 1022-1336
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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