Entropic chain effects on dynamic bonding reactions are shown to enable the tuning of reaction equilibria not only by changing the mass of the reactants, but also by merely altering the building block side chain structure and thus the intrinsic stiffness. The findings enable a step change for the design of on-demand bonding systems and reversible ligation chemistry in general.

We report a visible light responsive moiety capable of generating highly reactive thioaldehydes. Upon irradiation with visible light (420 nm) the pyreneacyl sulfide species undergoes a Norrish II elimination yielding thioaldehydes capable of being trapped by nucleophiles (amines, aminoxys, and thiols), as well as Diels-Alder processes, representing a new versatile ligation platform.

No abstract

We show that, all other conditions being equal, bond cleavage in the middle of molecules is entropically much more favored than bond cleavage at the end. Multiple experimental and theoretical approaches have been used to study the selectivity for bond cleavage or dissociation in the middle versus the end of both covalent and supramolecular adducts and the extensive implications for other fields of chemistry including, e.g., chain transfer, polymer degradation, and control agent addition are discussed. The observed effects, which are a consequence of the underlying entropic factors, were predicted on the basis of simple theoretical models and demonstrated via high-temperature (HT) NMR spectroscopy of self-assembled supramolecular diblock systems as well as temperature-dependent size-exclusion chromatography (TD SEC) of covalently bonded Diels-Alder step-growth polymers.

We introduce a novel approach for studying thermoreversible Diels–Alder networks by Temperature Dependent SEC.

We report the transfer of entropic chain length effects into the realm of supramolecular chemistry and thereby demonstrate a macromolecular method to tune the reaction equilibria of hydrogen bonding motifs via the application of substituents of differing lengths and masses while not altering the actual recognition units to achieve a difference in the degree of association. The supramolecular adducts are characterized via temperature-dependent nuclear magnetic resonance (NMR) spectroscopy.

We introduce dithiooxalates as efficient and catalyst-free thermoreversible hetero Diels–Alder linkers for applications in self-healing materials, organic sheets, mild ligation or complex architecture design.

No abstract