Regensburg 2022 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 10: Modeling and Simulation of Soft Matter (joint session CPP/DY)
DY 10.8: Vortrag
Montag, 5. September 2022, 17:00–17:15, H39
A cosolvent surfactant mechanism affects polymer collapse in miscible good solvents — •Swaminath Bharadwaj1, Divya Nayar1,2, Cahit Dalgicdir1, and Nico van der Vegt1 — 1Technische Universität Darmstadt, Germany — 2IIT Delhi, India
The coil-globule transitions of aqueous polymers are of profound significance in understanding the structure and function of responsive soft matter. In particular, the remarkable effect of amphiphilic cosolvents (which preferentially adsorb on the polymer surface) that leads to both swelling and collapse of stimuli responsive polymers is still hotly debated in the literature [1]. The predominant focus has been on the attractive polymer-(co)solvent interactions and the role of solvent-excluded volume interactions has been largely neglected. The solvent-excluded volume contribution to the solvation free energy corresponds to the formation of a repulsive polymer-solvent interface.
Using MD simulations, we herein demonstrate that alcohols reduce the free energy cost of creating a repulsive polymer-solvent interface via a surfactant-like mechanism which surprisingly drives polymer collapse at low alcohol concentrations. This hitherto neglected role of interfacial solvation thermodynamics is common to all coil-globule transitions [2], and rationalizes the experimentally observed effects of higher alcohols and polymer molecular weight on the coil-to-globule transition of thermoresponsive polymers [2]. This mechanism is generic and applicable to other solutions containing amphiphilic cosolvents or cosolutes.
References: [1] S. Bharadwaj et al., Soft Matter, 2022, 18, 2884. [2] S. Bharadwaj et al., Commun. Chem., 2020, 3, 165.