title: Hofmeister effect of sodium halides on the switching energetics of thermoresponsive polymer brushes.
abstract: A laser temperature-jump technique is used to probe the impact of sodium halides on the temperature-dependent switching kinetics and thermodynamics of poly(N-isopropylacrylamide) brushes. An analysis on the basis of a two-state model reveals van't Hoff enthalpy and entropy changes. Sodium halides increase the endothermicity and the entropic gain of the switching process below and above Tc following the Hofmeister series: NaCl > NaBr > NaI. In contrast, enthalpic and entropic changes at Tc remain virtually unaffected. This provides an unprecedented insight into the underlying switching energetics of this classic stimuli-responsive polymer. Because of its model character, these results represent an essential reference on the way to unpuzzle the molecular driving forces of the Hofmeister effect.
authors.affiliation: Fakultät für Chemie, Physikalische Chemie, Universität Duisburg-Essen, 45117 Essen, Germany.
authors.forename: Crispin Amiri
authors.initials: CA
authors.lastname: Naini
authors.forename: Marc
authors.initials: M
authors.lastname: Thomas
authors.forename: Steffen
authors.initials: S
authors.lastname: Franzka
authors.forename: Sven
authors.initials: S
authors.lastname: Frost
authors.forename: Mathias
authors.initials: M
authors.lastname: Ulbricht
authors.forename: Nils
authors.initials: N
authors.lastname: Hartmann
mesh_terms: D011108:Polymers / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D011108:Polymers