Unveiling the Role of Physicochemical Bonds on the Mechanical Behavior of Colloidal Gels

Soft materials are characterized by their intricate interplay of structure, dynamics, and rheological properties. This complexity makes it challenging to accurately predict their response to shear stress. Here, we investigate how the nature of colloidal bonds – entropic repulsion, physical entanglements, electrostatic attractions, and covalent bonds – affect the mechanical characteristics of gels. Our research aims to enhance our ability to engineer gels and colloidal suspensions with tailored responses and advanced functionalities by exploring the fundamental physics governing these responses. We selected diverse models that encompass a broad spectrum of materials, each possessing unique chemical bonds within their microstructure, such as cellulose nanocrystals modified with salt, bentonite, Carbopol, and cellulose nanofibers. We investigate the critical role played by these structural bonds and their response to linear and nonlinear deformations. Specifically, we apply our novel rheological approach – serial creep divergence (SCD) – to accurately determine the yield transition and critical stress and to reveal the physics and origin of yielding. This comprehensive approach allows for a detailed comparison of how these materials respond to shear stress, ultimately advancing our understanding of the intricate interplay between chemical bonding and material behavior within soft, amorphous materials.