Dresden 2026 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: French-German Session: Simulation Methods and Modeling of Soft Matter I

CPP 9.1: Hauptvortrag

Montag, 9. März 2026, 15:00–15:30, ZEU/LICH

Why Polymers Swell or Collapse: Molecular Insights into Cosolute Effects — •Nico van der Vegt — Department of Chemistry, Technical University of Darmstadt

Water-soluble amphiphilic polymers are widely used as stimuli-responsive materials. Their performance is governed by the coil-globule transition, characterised by the theta temperature, which can be tuned by adding small organic molecules (cosolutes). Although related phenomena - such as cononsolvency and salting-out - are well understood at a phenomenological level, their underlying molecular mechanisms remain unclear. This talk explores the solvation physics that determine how different classes of cosolutes influence the coil-globule transition of both generic hydrophobic polymers and realistic systems such as poly(N-isopropylacrylamide), using computer simulations. We identify two distinct molecular driving forces that regulate cosolute-induced hydrophobic interactions, leading to either polymer swelling or collapse. These driving forces depend sensitively on the relevant length scales and expose the interplay between microscopic and macroscopic solvation physics, underscoring the key role of solvent entropy in determining the properties of responsive soft-matter systems. [1] Comm. Chem. 3, 165 (2020), [2] PCCP 24, 2080-2085 (2022), [3] J. Chem. Phys. 160, 164902 (2024)

Keywords: thermoresponsive polymers; phase transition; cosolvents; water; hydrophobic interactions