Regensburg 2007 – wissenschaftliches Programm

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SYPE: Symposium Polyelectrolytes

SYPE 3: Polyelectrolytes II

SYPE 3.4: Hauptvortrag

Freitag, 30. März 2007, 11:30–12:00, H1

Polymers at Surfaces: Sticking and Gliding — •Roland Netz — Physics Department, TU Munich, 85748 Garching, Germany

Recently, peptides and different polyelectrolytes were pulled off from various low-dielectric and high-dielectric surfaces with the AFM, leading to a number of interesting observations: i) Surprisingly, the electrostatic contribution to the adsorption energy is always quite small, even for highly charged surfaces. The dominant solvation attraction can be quantitatively explained with classical MD simulations including explicit water. ii) Charge regulation of polymers at the surfaces is important and has to be taken into account for the quantitative modeling of adsorption energies. iii) Uncharged, hydrophobic surfaces appear negatively charged and give rise to sizable electrostatic adsorption energies. This finding is related to the water structure at hydrophobic substrates which involves an oriented first water layer and specific ion adsorption. iv) The friction coefficient of bound polymers is very low on hydrophobic substrates, which is traced back to the presence of a vacuum layer between substrate and water, which forms a lubricating cushion on which the polymers glide.