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Cascade Mechanochemical Transformation of a Benzobarrelane Polymer
Daniel C Lee1, Erica J Flear1, Rui Xu1,2,3
1Department of Chemistry, Stanford University, Stanford, California 94305, United States.
Journal of the American Chemical Society
|October 14, 2025
Summary
Cooperative mechanochemistry in polymers arises from connected benzobarrelane units. Force triggers radical cascades, transforming polymer backbones through novel pathways absent in isolated molecules.
Area of Science:
- Polymer Chemistry
- Mechanochemistry
- Materials Science
Background:
- Individual force-responsive molecules (mechanophores) are key in polymer mechanochemistry.
- Coupling specific molecular structures along a polymer backbone may unlock new reactivities.
- Benzobarrelane polymers offer a platform to explore cooperative mechanochemical effects.
Purpose of the Study:
- To investigate novel mechanochemical reactivity in polymers with closely coupled benzobarrelane units.
- To determine if connected barrelane structures exhibit unique force-induced transformations.
- To compare the mechanochemical performance of benzobarrelane polymers with highly strained systems.
Main Methods:
- Synthesis of a polymer featuring benzobarrelane repeat units linked by backbone alkenes.
- Application of mechanical force to induce bond scission and trigger radical cascade reactions.
- Analysis of polymer backbone structural transformation under force, comparing connected vs. isolated units.
Main Results:
- Force-induced bond scission in the benzobarrelane polymer initiated a radical cascade reaction.
- The polymer underwent significant backbone structural transformation, comparable to highly strained polyladderenes.
- Mechanochemical reactions were observed only when benzobarrelane units were immediately connected, not when distant.
Conclusions:
- Cooperative effects between adjacent benzobarrelane units enable novel polymer backbone transformations.
- This study demonstrates the potential for creating unique reactivities through designed molecular cooperation.
- Benzobarrelane polymers showcase a new strategy for polymer mechanochemistry beyond individual unit strain.
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