SKM 2021 – wissenschaftliches Programm

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SYSM: Symposium Topological constraints in biological and synthetic soft matter

SYSM 1: Topological constraints in biological and synthetic soft matter

SYSM 1.2: Hauptvortrag

Montag, 27. September 2021, 10:30–11:00, Audimax 1

Dynamics of macromolecular networks under topological and environmental constraints: some outstanding challenges — •Dimitris Vlassopoulos — FORTH and University of Crete, 100 N. Plastira St., Heraklion 70013, Greece

One of the biggest successes of soft matter physics has been the understanding of the rheological consequences of polymeric entanglements. It has set the stage for further advances which continue to date. Examples range from the viscoelastic spectrum of wormlike micelles to shear thinning of entangled polymers. Yet, a number of outstanding challenges remain, and here we present recent work addressing two of them: (i) Entangled linear polymers under strong shear exhibit a rich transient response whose interpretation remains controversial. We focus on the weak undershoot following the (well understood) overshoot of shear stress growth coefficient, which is often hard to detect experimentally. Modeling provides a rationalization by invoking the idea of tumbling which itself stems from simulation results. We designed a set of experiments with homopolymer blends to further elucidate its origin and identify the experimental and molecular parameters governing its appearance. (ii) Supramolecular assemblies based on hydrogen bonding motifs in apolar solvents exhibit rheological signatures which sensitively depend on traces (0.01%wt) of dissolved water. Hence, the relative humidity affects the viscoelastic response of the formed physical networks. We present results from linear and nonlinear rheometry which allow to quantify this overlooked effect and provide the ability to tune the rheology of supramolecular networks at molecular level.