Non-equilibrium adsorption at solid/liquid interfaces from polyelectrolyte solutions

Controlled synthesis of radiolabelled amine methacrylate water-soluble polymers with end-groups of varying hydrophobicity and studies of adsorption behaviour

Radioactive initiators of increasing hydrophobicity, including fluorescent initiators, have been used to conduct the ambient ATRP of poly(2-(diethylamino)ethyl methacrylate) and the behaviour of the resultant polymers has been monitored with respect to surface adsorption using radio-techniques; considerable effects of end group type were observed.

Adsorption of Polyelectrolyte versus Surface Charge: in Situ Single-Molecule Atomic Force Microscopy Experiments on Similarly, Oppositely, and Heterogeneously Charged Surfaces

We have studied the effect of the pH and surface charge of mica on the adsorption of the positively charged weak polyelectrolyte (PE) poly(2-vinylpyridine) (P2VP) using atomic force microscopy (AFM) single-molecule experiments. These AFM experiments were performed in situ directly under aqueous media. If the mica's surface and the PE are oppositely charged (pH > 3), the PE forms a flat adsorbed layer of two-dimensionally (2D) equilibrated self-avoiding random walk coils. The adsorbed layer's structure remains almost unchanged if the pH is decreased to pH 3 (the mica's surface is weakly charged). At pH 2 (the mica surface is decorated by spots of different electrical charges), the polyelectrolyte chains take the form of a 2D compressed coil. In this pH range, at an increased P2VP concentration in solution, the PE segments preferentially adsorb onto the top of previously adsorbed segments, rather than onto an unoccupied surface. We explain this behavior as being caused by the heterogeneous character of the charged surface and the competitive adsorption of hydronium ions. The further increase of polymer concentration results in a complete coverage of the mica substrate and the charge overcompensation by P2VP chains adsorbed on the similarly charged substrate, due to van der Waals forces.

Relaxation phenomena of hydrolyzed polyvinylamine molecules adsorbed at the silica/water interface

Surface area exclusion chromatography (SAEC) was employed to determine the individual relaxation of polymer molecules within a saturated heterogeneous layer composed of two polymers of different molecular characteristics. The investigations focused on three systems differing in molecular weight and/or hydrolysis grade. The molecular relaxation process was determined to be different within the heterogeneous layer when compared with the behavior of the same polymer in the homogeneous layer. The modifications in the relaxation process of a given polymer were imposed by the interfacial characteristics of the second polymer. Finally, in heterogeneous layers, the relative variation of the interfacial area of the two polymers is expressed in a single relationship.