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Fundamental understanding of mechanochemical reactivity is important for designing new mechanophores. Besides the core structure of mechanophores, substituents on a mechanophore can affect its mechanochemical reactivity through electronic stabilization of the intermediate or effectiveness of force transduction from the polymer backbone to the mechanophore. The latter factor represents a unique mechanical effect in considering polymer mechanochemistry. Here, we show that regioisomeric linkage that is not directly adjacent to the first cleaving bond in cyclobutane can still significantly affect the mechanochemical reactivity of the mechanophore. We synthesized three non‐scissile 1,2‐diphenyl cyclobutanes, varying their linkage to the polymer backbone via theo,m, orp‐position of the diphenyl substituents. Even though the regioisomers share the same substituted cyclobutane core structure and similar electronic stabilization of the diradical intermediate from cleaving the first C−C bond, thepisomer exhibited significantly higher mechanochemical reactivity than theoandmisomers. The observed difference in reactivity can be rationalized as the much more effective force transduction to the scissile bond through thep‐position than the other two substitution positions. These findings point to the importance of considering force‐bearing linkages that are more distant from the bond to be cleaved when incorporating mechanophores into polymer backbones.
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Mechanochemically accessing a challenging-to-synthesize depolymerizable polymer
Abstract Polymers with low ceiling temperatures ( T c ) are highly desirable as they can depolymerize under mild conditions, but they typically suffer from demanding synthetic conditions and poor stability. We envision that this challenge can be addressed by developing high- T c polymers that can be converted into low- T c polymers on demand. Here, we demonstrate the mechanochemical generation of a low- T c polymer, poly(2,5-dihydrofuran) (PDHF), from an unsaturated polyether that contains cyclobutane-fused THF in each repeat unit. Upon mechanically induced cycloreversion of cyclobutane, each repeat unit generates three repeat units of PDHF. The resulting PDHF completely depolymerizes into 2,5-dihydrofuran in the presence of a ruthenium catalyst. The mechanochemical generation of the otherwise difficult-to-synthesize PDHF highlights the power of polymer mechanochemistry in accessing elusive structures. The concept of mechanochemically regulating the T c of polymers can be applied to develop next-generation sustainable plastics.
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- PAR ID:
- 10399305
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 14
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41467-023-35925-2
