Nikos burger (Eindhoven University) is to present a seminar entitled: Influence of external fields and particle architecturein rheology and structure of (soft) colloids and associated polymeric networks

Understanding how microscopic structure governs the macroscopic rheology of soft and complex materials is essential for both fundamental studies of nonequilibrium systems and the design of advanced formulations. In this talk, I will discuss structure–rheology relationships across a broad range of systems, from self-assembled polymers and organoclay networks to ultralow-cross-linked microgels. Combining shear rheology with dynamic light scattering, passive microrheology, and X-ray scattering, we investigate how thermodynamic conditions, shear history, and internal particle architecture control viscoelasticity, yielding, relaxation, and dynamic arrest.

In self-assembled systems, pressure provides an additional thermodynamic control parameter that modifies molecular association and relaxation. Increasing pressure can accelerate gelation and stabilize molecular structures, while also slowing terminal relaxation and promoting entangled viscoelastic states. In organoclay dispersions and drilling fluids, particle morphology, composition, processing conditions, pressure, temperature, and shear history provide complementary routes for tuning gel formation, yield stress, viscosity, and aging.
Ultralow-cross-linked microgels further demonstrate that internal particle architecture can strongly influence dynamics: temperature-induced changes in particle structure can drive a transition from polymer-like behavior to a repulsive colloidal glass, even as the effective packing fraction decreases.

Together, these studies demonstrate that the rheology of soft colloids cannot be understood solely in terms of concentration or interparticle interactions. Instead, macroscopic mechanical behavior emerges from the interplay between molecular and particle architecture, and interparticle interactions. This unified perspective provides a framework for linking microscopic structure and dynamics to macroscopic mechanical properties and for developing strategies to understand and control the behavior of complex soft materials.