title: Temperature-regulated fluorescence and association of an oligo(ethyleneglycol)methacrylate-based copolymer with a conjugated polyelectrolyte--the effect of solution ionic strength.
abstract: Aqueous mixtures of a dye-labeled non-ionic thermoresponsive copolymer and a conjugated cationic polyelectrolyte are shown to exhibit characteristic changes in fluorescence properties in response to temperature and to the presence of salts, enabling a double-stimuli responsiveness. In such mixtures at room temperature, i.e., well below the lower critical solution temperature (LCST), the emission of the dye is strongly quenched due to energy transfer to the polycation, pointing to supramolecular interactions between the two macromolecules. Increasing the concentration of salts weakens the interpolymer interactions, the extent of which is simultaneously monitored from the change in the relative emission intensity of the components. When the mixture is heated above its LCST, the transfer efficiency is significantly reduced, signaling a structural reorganization process, however, surprisingly only if the mixture contains salt ions. To elucidate the reasons behind such thermo- and ion-sensitive fluorescence characteristics, we investigate the effect of salts of alkali chlorides, in particular of NaCl, on the association behavior of these macromolecules before and after the polymer phase transition by a combination of UV-vis, fluorescence, and (1)H NMR spectroscopy with light scattering and small-angle neutron scattering measurements.
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam , Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany.
authors.forename: Sahika
authors.initials: S
authors.lastname: Inal
authors.forename: Leonardo
authors.initials: L
authors.lastname: Chiappisi
authors.forename: Jonas D
authors.initials: JD
authors.lastname: Kölsch
authors.forename: Mario
authors.initials: M
authors.lastname: Kraft
authors.forename: Marie-Sousai
authors.initials: MS
authors.lastname: Appavou
authors.forename: Ullrich
authors.initials: U
authors.lastname: Scherf
authors.forename: Manfred
authors.initials: M
authors.lastname: Wagner
authors.forename: Michael Ryan
authors.initials: MR
authors.lastname: Hansen
authors.forename: Michael
authors.initials: M
authors.lastname: Gradzielski
authors.forename: André
authors.initials: A
authors.lastname: Laschewsky
authors.forename: Dieter
authors.initials: D
authors.lastname: Neher