Non-Gaussian Diffusion in Complex Media: From General Theory to Colloidal Transport in Glassy Soft-Hard Mixtures

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• Dr Vittoria Sposini, University of Padova
• Wednesday 29 October 2025, 14:30-15:30
• Unilever Lecture Theatre, Yusuf Hamied Department of Chemistry.

If you have a question about this talk, please contact Lisa Masters.

Transport phenomena in soft matter systems play a fundamental role in a wide range of biological and industrial processes. Over the last decades, it has become clear that the motion of diffusive tracers in complex and disordered environments often deviates from classical Gaussian statistics described by standard Brownian motion, instead exhibiting (almost) universally non-Gaussian behaviour. Both analytical and numerical studies have linked non-Gaussian diffusion to sample-to-sample variability and/or spatio-temporal heterogeneity inherent to the system. This seminar aims to explore this phenomenon from two distinct yet complementary perspectives. In the first part, I will present a general theoretical framework based on the concept of subordination, which captures the emergence of non-Gaussian diffusion across a broad class of complex systems. In contrast, the second part will focus on a specific case study, investigating how system heterogeneity influences the emergence of non-Gaussian diffusion in the transport of colloidal nanoparticles through a polymeric glassy matrix composed of star polymers. In particular, I will show that the emergence of arrested phase separation in this system interacts with the dynamics of hard spheres in a non-trivial manner, representing another possible source of effective non-Gaussian diffusion. Overall, these two perspectives together highlight the importance of system heterogeneity in shaping transport behaviour in complex media.

References:

[1] V. Sposini, S. Nampoothiri, A. Chechkin, E. Orlandini, F. Seno, and F. Baldovin, Phys. Rev. Lett. 132, 117101 (2024). [2] V. Sposini, S. Nampoothiri, A. Chechkin, E. Orlandini, F. Seno, and F. Baldovin, Phys. Rev. E 109 , 034120 (2024). [3] K. Moser, C.N. Likos, V. Sposini, in preparation.

This talk is part of the Theory - Chemistry Research Interest Group series.

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