Berlin 2012 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 10: Interfaces and Thin Films II
CPP 10.4: Talk
Tuesday, March 27, 2012, 10:30–10:45, C 130
Temperature-induced transition from odd-even to even-odd effect in polyelectrolyte multilayers due to interpolyelectrolyte interactions — •Peter Nestler1, Stephan Block2, and Christiane A. Helm1 — 1Institut für Physik, Uni Greifswald, Felix-Hausdorff-Str. 6, 17487 Greifswald, Germany — 2ZIK HIKE, Uni Greifswald, Fleischmannstr. 42 - 44, D-17487 Greifswald, Germany
Within a liquid cell the linear growth of polyelectrolyte multilayers by LbL technique is observed using multiple angle null-ellipsometry. Poly(styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) are used. The salt content is varied between 1 and 4 mol/L NaCl, the temperature between 20 and 55∘C. The outermost layer is investigated. At low temperature a top PSS layer is twice as thick as a top PAH layer (odd-even effect), consistent with the respective monomer volume and the same water content for both polyelectrolytes. On heating, the thickness of a polycation/polyanion bilayer increases. For temperatures exceeding Tx−over a top PAH layer is thicker than a top PSS layer (even-odd effect). In this case, the index of refraction of the respective top layers indicates a compact PSS and a swollen PAH layer. At temperatures above Tx−over the dried films destabilize, an increased roughness and a random pattern of holes is observed. It is suggested that at elevated temperature and high salt-conditions, secondary forces gain importance in comparison to electrostatic forces: therefore a transition from an odd-even to an even-odd effect occurs, as well as the decreased film stability on drying.