SKM 2021 – wissenschaftliches Programm
CPP 8.8: Poster
Mittwoch, 29. September 2021, 17:30–19:30, P
Conformation and packing of polyanions in polelyectrolyte complexes - a combined PFG and solid-state NMR study — Benjamin Kohn, Carolin Naas, Uwe Lappan, and •Ulrich Scheler — Leibniiz-Institut für Polymerforschung Dresden e.V, Dresden, Germany
Polyelectrolyte complexes find wide applications in surface modificationand controlled drug delivery. In the highly charged states direct ion pairing between polycation and polyanion is expected. The conformation of a weak polyanion depends on pH and ionic strength. The effective charge is determined from electrophoresis NMR, PFG NMR yields the hydrodynamic size as a measure for the conformation. Separating 1H MAS spectra in two-dimensional single-quantum-double-quantum correlation spectra identifies acid protons hydrogen bonded to other acid protons and thus and polyanion-rich regions in the complexes. At low pH this are reduced by a factor of three in the complexes compared to the pure polyanion. At higher pH (high nominal charge) with a more stretched conformation almost none acid-acid contacts are found in the complexes. In the 22Na spectra signals from NaCl and sodium maleate are distinguished and quantified. Even at the highest pH when all of the polyanion is dissociated about one quarter of the sodium is detected in maleate in the complexes. This extrinsic charge compensation shows that in any case there is no straight ion pairing between the polycation and polyanion, phases of pure polyanion remain.