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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Poster Session I

CPP 24.47: Poster

Montag, 16. März 2020, 17:30–19:30, P3

Increase of the diffusion constant of polyanion PSS in polyelectrolyte multilayers on approach to the glass transition temperature in dependence of salt concentration and pH — •Annekatrin Sill, Sven Neuber, and Christiane A. Helm — University Greifswald, Institute of Physics, Germany

Using neutron reflectivity, the vertical diffusion of polyanion PSS within polyelectrolyte multilayers is probed. We used a slab architecture with selective polyanion deuteration. The temperature-, salt- and pH-dependent change of the diffusion constant was determined. The films were measured as prepared and after annealing for different times (i) in 1 M NaCl solution at different temperatures approaching the glass transition at 55°C, (ii) at 40°C and different NaCl concentrations of the annealing solution and (iii) in 100 mM NaCl solution with different pH values. As the temperature of the annealing solution increases, the diffusion constant increases by five orders of magnitude. If the salt concentration in the annealing solution is reduced, the diffusion constant becomes smaller by two orders of magnitude. Preliminary measurements show that the diffusion constant decreases as the pH of the annealing solution increases. We conclude that for a large diffusion constant not only electrostatic monomer/monomer bonds need to be replaced by monovalent/ion bonds, but the most important effect is the increased mobility of the water molecules on approach to the glass transition temperature.