52 research outputs found
A Mechanochemical Reaction Cascade for Controlling Load-Strengthening of a Mechanochromic Polymer
We demonstrate an intermolecular reaction cascade to control the force which triggers crosslinking of a mechanochromic polymer of spirothiopyran (STP). Mechanochromism arises from rapid reversible force-sensitive isomerization of STP to a merocyanine, which reacts rapidly with activated C=C bonds. The concentration of such bonds, and hence the crosslinking rate, is controlled by force-dependent dissociation of a DielsâAlder adduct of anthracene and maleimide. Because the adduct requires ca. 1 nN higher force to dissociate at the same rate as that of STP isomerization, the cascade limits crosslinking to overstressed regions of the material, which are at the highest rate of material damage. Using comb polymers decreased the minimum concentration of mechanophores required to crosslinking by about 100-fold compared to previous examples of load-strengthening materials. The approach described has potential for controlling a broad range of reaction sequences triggered by mechanical load
Stable PyrroleâLinked Bioconjugates through TetrazineâTriggered Azanorbornadiene Fragmentation
A Simple Method for the Visualization of Chair and Twist-Boat Transition States in Torsionally Controlled Addition Reactions
Formation of Active Cyclic Fiveâmembered Frustrated Phosphane/Borane Lewis Pairs and their Cycloaddition Reactions
Stable PyrroleâLinked Bioconjugates through TetrazineâTriggered Azanorbornadiene Fragmentation
Cyclic Alkyne Approach to HeteroatomâContaining Polycyclic Aromatic Hydrocarbon Scaffolds
Cyclic Alkyne Approach to HeteroatomâContaining Polycyclic Aromatic Hydrocarbon Scaffolds
Mild IridiumâCatalysed Isomerization of Epoxides. Computational Insights and Application to the Synthesis of βâAlkyl Amines
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