SKM 2023 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 11: Poster Session I

BP 11.38: Poster

Dienstag, 28. März 2023, 12:30–15:30, P1

Self-patterning of polyelectrolyte multilayer films: the roles of PSS molecular weight, the top layer, and post-preparation treatment — Amir Azinfar and •Christiane A. Helm — Institute of Physics, University of Greifswald, Germany

The self-patterning of thin films is relevant both for fundamental research and applications. We investigate polyelectrolyte multilayer films made from poly(diallyldimethylammonium) and poly(styrene sulfonate) (PDADMA/PSS). Various PSS with low molecular weight were used. Invariably, the film thickness increases exponentially with the number of deposited PDADMA/PSS bilayers. The separation and height of the domains increase significantly with each deposited PDADMA/PSS bilayer, as AFM images show. At the end of the exponential growth regime, either a parabolic (and then a linear) or a linear growth regime follows, depending on the selected PSS molecular weight. In the non-exponential growth regimes, the domain separation changes less during film growth than in the exponential growth regime.

PSS is more strongly bound to the film than PDADMA. PSS-terminated films show the same domain distance in water and air. However, when PDADMA-terminated films are dried, the domain distance in the air increases while the domain height decreases, causing a reduction in total area. In the air, the surface energy is greater than in water, and a highly textured surface costs a lot of energy. We propose the changed surface pattern is attributable to energy minimization. Furthermore, the domains are stable when exposed to 1 M NaCl solution but shrink in 2 M NaCl.