Bis‐carbonylimidazolide (BCI) functionalization enables an efficient synthetic strategy to generate high molecular weight segmented nonisocyanate polyurethanes (NIPUs). Melt phase polymerization of ED‐2003 Jeffamine,4,4′‐methylenebis(cyclohexylamine), and a BCI monomer that mimics a 1,4‐butanediol chain extender enables polyether NIPUs that contain varying concentrations of hard segments ranging from 40 to 80 wt. %. Dynamic mechanical analysis and differential scanning calorimetry reveal thermal transitions for soft, hard, and mixed phases. Hard segment incorporations between 40 and 60 wt. % display up to three distinct phases pertaining to the poly(ethylene glycol) (PEG) soft segment
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.
more » « less- Award ID(s):
- 1925539
- NSF-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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