Dynamic exchange in vinylogous urethane vitrimers: computational and experimental approaches to screen structure–property relationships of dynamic bonds

Abstract

The rheological properties of vitrimers are known to be dependent on the rate of dynamic bond exchange within the polymer network. This work explores the use of computational and experimental approaches to screen the chemical design space available for vinylogous urethane vitrimers in order to tailor stress relaxation behavior. Density functional theory (DFT) is used to analyze the effects of changing the nature of substituents and to identify functional groups that are potentially capable of catalyzing the dynamics of bond exchange. These effects are then confirmed by NMR experiments on small molecules in a dynamic pool of reacting species. Confirmation that these effects of tuning dynamic bond exchange rates in small molecules are translated to the final polymer networks is achieved through the synthesis of a series of vinylogous urethane vitrimers containing different functional groups in the vicinity of the dynamic bond. The stress relaxation behavior of the vitrimers confirms that the dynamic behavior seen in DFT and kinetic studies of small molecules is also seen in the final material.