Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 54: Poster Session 3
CPP 54.22: Poster
Donnerstag, 3. April 2014, 15:00–19:00, P2
Thermodynamic Description of the LCST of Charged Thermoresponsive Copolymers — •Jan Heyda1 and Joachim Dzubiella1,2 — 1Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany — 2Department of Physics, Humboldt-University Berlin, Newtonstr. 15, 12489 Berlin, Germany
The dependence of the lower critical solution temperature (LCST) of charged, thermosensitive copolymers on their charge fraction and the salt concentration is investigated by employing systematic cloud-point experiments and analytical theory. The latter is based on the concept of the Donnan equilibrium incorporated into a thermodynamic expansion of a two-state free energy around a charge-neutral reference homopolymer and should be applicable for weakly charged (or highly salted) polymer systems. Very good agreement is found between the theoretical description and the experiments for aqueous solutions of the responsive copolymer poly(NIPAM-co-EVImBr) for a wide range of salt concentrations and charge fractions up to 8%, using only two global, physical fitting parameters.
In addition, the prediction of salt-specific contribution to LCST is presented in the framework of so called partitioning concept. Inserted into thermodynamic expansion, a novel interpretation of LCST, and cloud point measurements is revealed. In particular, salt effects on transition thermodynamics are obtained for established polymers; PNIPAM or elastine-like-polypeptides.