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Abstract The intrinsic reversibility of dynamic covalent bonding, such as the furan‐maleimide Diels‐Alder (DA) cycloaddition reactions, enables reprocessable, self‐healing polymer materials that can be reconfigured via the mechanism of solid‐state plasticity. In this work, the temperature‐dependent exchange rates of stereochemically distinctendoandexoDA bonds are leveraged to achieve tunable, temperature‐ and stress‐activated shape morphing in Diels‐Alder polymer (DAP) networks. Through thermal annealing, ≈35% ofendoDA isomers are converted in neat DAP networks to the thermodynamically favoredexoform, achieving ≈97%exoafter complete annealing at 60 °C. This conversion results in a ≈1.7 fold increase in elastic modulus, from 1.7 to 3.0 MPa, and significantly alters the stress relaxation and shape recovery behavior. Spatially resolved annealing, is further showcased enabling the precise control of spatial distributions ofendoandexoDA bonds across planar geometries. The locally distinct concentrations ofendo/exoisomers, achieved by temperature‐induced conversion ofendoDA isomers to the thermodynamically stableexoDA isomers, gave rise to the spatial distributions of stress relaxation rates and elastic strain recovery mismatch to enable controlled stereochemical shape morphing. This approach provides a simplified, thermally driven method for shape morphing, with potential applications in soft robotics and flexible electronics.
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Investigating Cavity Quantum Electrodynamics-Enabled Endo/Exo- Selectivities in a Diels-Alder Reaction
Coupling molecules to a quantized radiation field inside an optical cavity has shown great promise in modifying chemical reactivity. It was recently proposed that strong light-matter interactions are able to differentiate endo/exo products of a Diels-Alder reaction at the transition state. Using the recently developed parameterized quantum electrodynamic \textit{ab initio} polariton chemistry approach along with time-dependent density functional theory, we theoretically confirm that the ground state selectivity of a Diels-Alder reaction can be fundamentally changed by strongly coupling to the cavity, generating preferential endo or exo isomers which are formed with equal probability for the same reaction outside the cavity. This provides an important and necessary benchmark with the high-level self-consistent QED coupled cluster approach. In addition, by computing the ground state difference density, we show that the cavity induces a redistribution of electron density from intramolecular $$\pi$$-bonding orbitals to intermolecular bonding orbitals, thus providing chemically relavent description of the cavity-induced changes to the ground state chemistry and thus changes to the molecular orbital theory inside the cavity. We extend this exploration to an arbitrary cavity polarization vector which leads to critical polarization angles that maximize the endo=/exo selectivity of the reaction. Finally, we decompose the energy contributions from the Hamiltonian and provide discussion relating to the dominent dipole self-energy effects on the ground state.
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- Award ID(s):
- 2124398
- PAR ID:
- 10578951
- Publisher / Repository:
- ChemRxiv
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Posted Content:
- https://doi.org/10.26434/chemrxiv-2024-6xsr6
