Static and Dynamic Forces between Adsorbed Polyelectrolyte Layers (Quaternized Poly-4-vinylpyridine)
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Static forces (a combination of steric and electrostatic interactions) and dynamic shear forces (resulting from interactions between polymer chains) were measured between quaternized poly-4-vinylpyridine layers (QPVP) adsorbed onto mica from 1 mM borate buffer with or without added 0.25 M NaCl. At the polyelectrolyte concentration chosen. 0.4 mg mL-1 extended layers were formed at all adsorption conditions. The adsorbed amount of 98% quaternized poly-4-vinylpyridine was lower at low ionic strength than of 14% quaternized, and increased with added salt. Layers formed by one-step adsorption showed a predominantly elastic response to small-amplitude oscillatory shear in the frequency range 0.13-130 Hz. In the case of two-step adsorption, the confined layers allowed viscous dissipation of similar magnitude as the elastic, which suggests that additional chains adsorbing at high salt concentration onto a preformed layer had fewer segments in contact with the solid surface.
author list (cited authors)
Ruths, M., Sukhishvili, S. A., & Granick, S.