A Strategy toward Cyclic Topologies Based on the Dynamic Behavior of a Bis(hindered amino)disulfide Linker

Abstract

A simple and efficient method to generate macrocyclic structures has been developed based on the dynamic behavior of the linker bis(2,2,6,6‐tetramethylpiperidin‐1‐yl)disulfide (BiTEMPS). The prime linear structure was transformed into a (macro)cycle using the following sequence: 1) thiol–ene reaction with a BiTEMPS derivative to afford the linear precursor, then 2) an entropy‐driven transformation induced by diluting and heating. The radicals generated from BiTEMPS upon heating are highly tolerant toward a variety of chemical species, including oxygen and olefins, but they exhibit high reactivity in exchange reactions, which can be applied to the topology transformation of various skeletons. The advantages of the present method, namely, its procedural simplicity and substrate versatility, are demonstrated by the gram‐scale synthesis of cyclic compounds with low and relatively high molecular weight.

Swelling‐induced Mechanochromism in Multinetwork Polymers

“…Many studies have reported that dynamic covalent bonds in a highly mobile environment exist in their thermodynamically stable state. For example, the equilibrium of dynamic covalent bonds is highly biased toward the associated state at ambient temperature; when they are implemented in highly mobile networks such as those of gels [81–84] and rubbery network polymers, [83–89] they undergo exchange reactions to endow the materials with self‐healing and reorganization characteristics [90–93] . In contrast, in environments with limited chain mobility, i.e., glassy polymer matrices [35, 50, 51, 78] frozen gels, [64–67] crystalline polymers, [62, 63] and heterointerfaces, [94] the presence of thermodynamically unstable dissociated species, which are produced by mechanical stimuli, can be observed by means of chromism or specialized techniques due to the diffusion‐controlled reassociation.…”