Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 22: POSTER C

CPP 22.63: Poster

Donnerstag, 27. März 2003, 12:00–14:00, ZEU/250

Surface and Mechanical Properties of Polyelectrolyte Multilayers investigated with AFM — •Vera Bosio and Andreas Fery — Max-Planck-Institute of Colloids and Interfaces, D-14424 Potsdam

Our work has been focusing on understanding and quantifying the architecture of polyelectrolyte multilayers, especially the double-layer electrostatic interaction between equally charged layers, as a function of the number of layers. Polyelectrolytes used in the experiments are PEI-Polyethylenimine and PAH-Poly(allylamine hydrochoride) as polycations and PSS-Poly(sodium 4-styrensulfonate) as polyanion. Force/Distance Curves have been performed using an Atomic Force Microscope with the colloidal probe technique. Polyelectrolyte multilayers have been deposited on SiO2 spherical beads in the micrometer range (3-8 micron diameter), then used as AFM probe. The interaction of such a probe with a flat substrate, consisting in a Si/SiO2 wafer coated with the same polyelectrolytes is then investigated. The well defined geometry of the probe, i.e. its spherical shape, and its size, make it possible to determine its radius exactly even by means of a normal optical microscope and allow to quantify the interaction energy using the Poisson-Boltzmann Equation, as well as learning about the charge regulation taking place on the surface. At the same time, we want to take into account the possible deformations occurring under stress, that is the mechanical properties of the material. The stiffness of the multilayers in aqueous solution has been investigated with AFM using the Pulse Force Mode Technique.