Regensburg 2016 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 48: Focus: The Physics of Water Interactions with Biological Matter (joint session BP/CPP, organized by CPP)
CPP 48.4: Talk
Thursday, March 10, 2016, 10:45–11:00, H37
Salt Induced Hydrophobic Polymer Collapse Theoretical Model vs. Simulation — •Jan Heyda1 and Joachim Dzubiella2,3 — 1Department of Physical Chemistry, University of Chemistry and Technology, Prague, Czech Republic — 2Soft Matter and Functional Materials, Helmholtz- Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany — 3Department of Physics, Humboldt-University Berlin, Newtonstr. 15, 12489 Berlin, Germany
Smart materials are perspective due to their versatility. An soft-matter example are thermoresponsive polymers, which undergo volume transition, when crossing the lower critical solution temperature (LCST). Near the LCST, they become sensitive to other stimuli, such as salt type and concentration (dx.doi.org/10.1021/ja0546424).
In this contribution, we employed a hydrophobic polymer model (dx.doi.org/10.1073/pnas.0605139104), which possesses 2-state behavior, to study ion-specific effects. We performed replica-exchange molecular dynamics simulations and analyzed the data thermodynamically as well as in terms of Kirkwood-Buff theory, i.e., the preferential binding of salt over water to the polymer was determined.
We have found that the effect on LCST change of salts excluded from hydrophobic interfaces, such as KF and NaCl is strikingly different from attracted salts, such as NaI or GndCl. The surface area based model performs well for the first, but fail for the second group of salts.
To interpret the effect of 'binding' salts, we have employed recently proposed bridging mechanism (dx.doi.org/10.1021/ma302320y) and chain configuration entropy approach (dx.doi.org/10.1039/c4cp05314a).