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arXiv · 2610.29389

Tuning Thermal Memory and Dissipation in Colloidal Glasses via Microgel Particle Stiffness

Sonali Vasant Kawale·Ranjini Bandyopadhyay
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Abstract

The Kovacs effect, characterized by nonlinear, path-dependent structural recovery, is a hallmark of glassy systems. In soft colloidal microgel glasses, the stiffness of the constituent particles governs their deformation, swelling, rearrangement, and response to external stimuli, thereby dictating the path-dependent structural recovery of these jammed non-equilibrium systems. To investigate this influence, microgels of different stiffnesses were synthesized by adjusting the concentration of the polar crosslinker, N, N'-methylenebisacrylamide (MBA). The relaxation of the storage and loss moduli was measured using oscillatory rheology under diverse temperature ramp rates, and cryo-FESEM imaging provided direct visualization of the underlying particle packing. While the rapid adaptability of soft particles and the kinetic arrest of stiff ones suppresses Kovacs asymmetry, intermediate-stiffness particles exhibit moderate thermoresponsivity, traversing distinct energy landscapes on heating and cooling to maximize asymmetry and dissipation. Cryo-FESEM micrographs, displaying gel-like networks in soft particle suspensions, dense packing in stiff particle suspensions, and disordered, compact structures in intermediate-stiffness systems, corroborate these findings. Our results demonstrate that intermediate-stiffness PNIPAM microgels optimize structural recovery, rendering them promising candidates for forming colloidal glasses and establishing Kovacs asymmetry as a robust probe of non-equilibrium dynamics in glassy systems.

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Sonali Vasant Kawale, Ranjini Bandyopadhyay. 2026-10-21. Tuning Thermal Memory and Dissipation in Colloidal Glasses via Microgel Particle Stiffness. https://arxiv.org/abs/2610.29389

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