Single molecule experiments visualizing adsorbed polyelectrolyte molecules in the full range of mono- and divalent counterion concentrations.

This work provides direct experimental verification (on the level of single molecules) for the behavior of hydrophobic polyelectrolyte chains adsorbed at a solid-liquid interface in the full range of possible salt concentrations: (a) in a dilute salt solution, PE chains possess an extended coil conformation visualized as adsorbed 2D-equilibrated coils; (b) in a moderate salt concentration range, the polymer coil shrinks and approaches the dimensions of a polymer coil under θ-conditions and the chains are visualized as adsorbed 3D-projected coils; (c) at high salt concentrations, the polymer coils reexpand and the molecules are visualized as 2D-equilibrated extended coils; however, (d) reexpansion is limited in the presence of multivalent counterions, presumably due to the bridging of the polymer coils by the counterions.

Invertible architectures from amphiphilic polyesters.

We synthesized and characterized novel amphiphilic polyesters with both hydrophilic and hydrophobic functionalities. The polyesters are soluble in organic and aqueous media and reveal the formation of inverse architectures whose behavior could be correlated to their chemical structure. We foresee that the amphiphilic properties of the polyesters reported here are obviously the basis of new architectures both in solution and on the solid surfaces, which could be used in a broad range of applications. The described synthesis of the copolymers is very simple and is based on commercially available products. That makes this approach attractive in various uses.

Graft polymerization from a silica surface initiated by adsorbed peroxide macroinitiators. I. Adsorption and structure of the adsorbed layer of peroxide macroinitiators on a silica surface.

The adsorption features of two peroxide macroinitiators (PMIs) with various functionalities from their semi-dilute solutions on the silica surface were thoroughly investigated in the present work. These investigations include the study of the adsorption kinetics of PMI in diverse solvents and a detailed examination of the adsorbed layer structure with the aid of ellipsometry, scanning force microscopy (SFM), and contact angle measurements. Rearrangements of PMI macromolecules at the solid surface are supposed to be the main reason for the appearance of extremes on the kinetic curves and, besides, have a more pronounceable effect on adsorption rate than their diffusion rate to the surface even at the initial stage of the process. Both island-like and densely packed structures of absorbed layers were revealed by combining contact angle measurements and SFM. Surprisingly, even in the case when saturation of the adsorbed layer is reached, PMI does not completely occupy the substrate surface which is at least particularly reachable for the wetting liquids. PMIs adsorbed at the solid surface are intended for the formation of tethered polymer "brushes" via the initiation of "grafting from" polymerization.