Probing glass transition of clay colloids by NMR relaxometry: Interplay between fluid Brownian dynamics and particle jamming

Using field cycling NMR relaxometry, we show how the slow water dynamics in the proximity of a colloidal surface provides an original way to follow the glass transition and the strong rotational slowing-down of a colloidal system made of plate-like laponite particles, a synthetic clay. The interplay between fluid Brownian loops near colloidal interfaces (which follows a Levy statistics) and particle dynamics is discussed. We propose an analytical model of the NMR relaxometry involving elementary time steps of the fluid dynamics near a colloidal interface (e.g., bulk loops, adsorption trains, escaping tails) coupled to the rotational dynamics of the particle. This close-form model is supported by our experimental data.