Dr. Véronique Trappe "Co-nonsolvency at the transition between solvation mechanisms"
Department of Physics, University of Fribourg, Switzerland
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When |
Feb 11, 2015 from 02:15 PM to 03:00 PM |
Where | Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg |
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Co-nonsolvency denotes the rather unusual instance that a polymer is insoluble in a binary solvent mixture, but perfectly soluble in the two solvents of which the mixture is composed of. We investigate this phenomenon for poly-N-isopropyl acrylamide (PNiPAM) in water/alcohol mixtures and demonstrate that co-nonsolvency is here the result of two distinct solvation mechanisms governing the phase behavior of PNiPAM in respectively water-rich and alcohol-rich environments.[1,2]. While the mixing contributions governing the phase behavior of classical polymer solutions determine the phase behavior of PNiPAM in alcohol-rich environments, in water-rich environments it is the energetic gain for the solvent to hydrate the hydrophobic groups of PNiPAM that governs the phase behavior. In the intermediate range of solvent composition the solvation of PNiPAM does neither lead to a sufficient decrease in the solvent energetics nor are the polymer mixing contributions sufficiently large to allow for the formation of a homogeneous solution.
[1] I. Bischofberger, D. C. E. Calzolari, V. Trappe, Co-nonsolvency of PNiPAM at the transition between solvation mechanisms.,Soft Matter 10 (2014) 8288
[2] I. Bischofberger, D. C. E. Calzolari, P- De Los Rios, I. Jelezarov, V. Trappe,Hydrophobic hydration of poly-N-isopropyl acrylamide: a matter of the mean energetic state of water., Sci. Rep. 4 (2014) 4377