Colloidal gel systems have many applications in modern research e.g. food science, cosmetics, construction materials, and medical applications, such as cartilage replacements. Current understandings of structural dynamics of these systems are limited to long-term effects, and as such there have been recent investigations using simulation-based arguments for addressing the various transport phenomena leading to mechanical stability and the associated structure. Due to complications with<i> in situ</i> probing of complex fluid materials from solvent phase interference and accurate tracking of particle motion, experimental support for proposed mechanisms is largely lacking. Here, we investigate the surface structure and response of a poly(methacrylamide-co-methacrylic acid) gel, which exhibits a glassy colloidal structure, to various stimuli including pH, temperature, electrostatic potential, and salt concentration, using a variety of <i>in-situ</i> atomic force microscopy techniques complemented by rheology, ATR-FTIR, and contact angle measurements. This system is particularly of interest due to the physical crosslinking of the system and delicate balance of inter and intraparticle forces during and post-synthesis leading to significant structural manipulation. Further, we demonstrate the applicability of this type of system as a semi-reversible responsive tribological interface.

Probing interfacial structural dynamics of charged glassy gels

ACS Spring 2022

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