Dresden 2026 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 13: Charged Soft Matter, Polyelectrolytes and Ionic Liquids
CPP 13.6: Talk
Monday, March 9, 2026, 16:30–16:45, ZEU/0260
Dissociation of weak polyacid systems in solution and brush coatings determined by IR titration — •Martin Müller1,2, Luise Wirth1,2, Birgit Urban1, Leo Dagand1,2, Alexander Münch1, and Petra Uhlmann1 — 1Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, Dresden D-01069, Germany — 2Technische Universität Dresden, Dresden D-01062, Germany
The dissociation degrees a of poly(acrylic acid) (PAA) and propionic acid (PA) solutions were determined by infrared (IR) titration and potentiometric (POT) titration concept. Stepwise increasing pH value from 2 to 12 by adding NaOH portions, IR spectra of PAA and PA show decrease of n(C=O) band due to carboxyl (COOH) and increase of n(COO-) band due to carboxylate (COO-) groups. From the respective normalized band integrals A, dissociation degree was calculated according to a=A(COO-)/(A(COOH)+A(COO-)). Plotting pH versus a and fitting by modified Henderson-Hasselbalch equation according to pH=pKa+B*log(a/(1-a)) the parameters pKa and B were determined. The slight pKa deviation found for IR and POT titration, the respective deviation between monomeric PA and polymeric PAA and the PAA molecular weight trend (PAA-2K, PAA-50K, PAA-450K) are discussed considering the two-phase model of polyelectrolyte solutions and Gibbs-Donnan theory. Furthermore, a and pKa of thin PAA brush coatings under aqueous ambient and the influence of metal ion type (Na+, Ca++, Ce+++) and concentration were determined by FTIR titration revealing higher pKa values compared to solution state and significant effects of ion valency on a.