Small-Molecule Investigation of Diels-Alder Complexes for Thermoreversible Crosslinking in Polymeric Applications

J Org Chem. 2021 Jul 2;86(13):8933-8944. doi: 10.1021/acs.joc.1c00855. Epub 2021 Jun 21.

Abstract

Combinations of dienes and dienophiles were examined in order to elicit possible combinations for thermoreversible crosslinking units. Comparison of experimental results and quantum calculations indicated that reaction kinetics and activation energy were much better prediction factors than change in enthalpy for the prediction of successful cycloaddition. Further testing on diene-dienophile pairs that underwent successful cycloaddition determined the feasibility of thermoreversibility/retro-reaction of each of the Diels-Alder compounds. Heating and testing of the compounds in the presence of a trapping agent allowed for experimental determination of reverse kinetics and activation energy for the retro-reaction. The experimental values were in good agreement with quantum calculations. The combination of chemical calculations with experimental results provided a strong insight into the structure-property relationships and how quantum calculations can be used to examine the feasibility of the thermoreversibility of new Diels-Alder complexes in potential polymer systems or to fine-tune thermoreversible Diels-Alder systems already in use.