Understanding vitrimer properties through various aspects of inhomogeneity

Vitrimers represent a unique class of cross-linked materials characterized by an associative bond exchange mechanism within their polymeric network structure. This bond exchange facilitates the diffusion of network chains upon the application of suitable stimuli, typically heat, thus enabling specific vitrimer properties such as stress relaxation and creep. Recent reviews have extensively documented the diverse molecular designs and valuable sustainable functionalities achieved through this nature of bond exchange. Numerous fundamental studies have focused on developing tuning methods for vitrimer properties, utilizing model vitrimers that assume homogeneous network structures with uniformly distributed bond exchange units. In contrast, some research groups currently have deliberately engineered inhomogeneous network structures, characterized by highly localized bond exchangeable units and the presence of constraints imposed by permanent cross-links. In this review, we emphasize the significance of inhomogeneous network systems as potential avenues for the versatile tuning of vitrimer properties, which could contribute to a deeper understanding of these materials.