ИСТИНА

Mixing aqueous solutions of oppositely charged polyelectrolytes leads to the formation of interpolyelectrolyte complexes (IPECs) due to cooperative electrostatic interactions between polycations and polyanions. These IPECs can be either soluble or insoluble in water depending on charge ratio Z (Z = [-]/[+]). If the charge ratio of the polyionic components exceeds a certain threshold value Z*, the generated IPECs are insoluble and typically precipitate. The significant progress in controlled synthesis of well-defined branched polymers opened new fields of possibilities for development of IPECs. We investigated the behavior of IPECs based on star-shaped polyelectrolytes and cross-linked spherical polyelectrolyte microgel networks in aqueous media. Both show a huge potential in different fields like drug delivery, design of biomaterials, and in the development of sensors. A miktoarm star polymer consisting of one poly(ethylene oxide) (PEO) and on average 2-3 poly([2-(methacryloyloxy)ethyl]trimethylammonium halides) (PMOTAH)-arms is introduced. The PEO ensures the solubilization of the formed IPECs and can increase the Z*-value significantly. In contrast to IPECs based on homopolyelectrolyte stars, the formed IPECs of the miktoarm stars do not precipitate by exceeding the threshold value Z*. By means of in situ TEM we could observe a rare vesicular morphology of these IPECs in their liquid environment. The preparation of "standard" vesicles made up of amphiphiles often requires special treatment (e.g., preparation via a common solvent; rehydration of dry lamellar films). The spontaneous formation (by simple mixing of the ionic counterparts) of unilamellar vesicles in general and hollow IPECs in particular is strongly desired for uptake and release applications. As another polyelectrolyte structure we studied quaternized cationic microgels and used them as a soft template for layer by layer (LbL) assemblies. The quaterniyed microgels are colloidally stable and because of their permanent charge, these microgels are pH-independent. Coating these charged microgels with polyelectrolytes influences the microgels size and electrophoretic mobility. The electrophoretic mobility reveals charge reversal after each layer deposition, clearly indicating polyelectrolyte adsorption at the microgel surface. The hydrodynamic radius decreases upon adsorption of the first layer and increases upon adsorption of the second layer. All this indicates that the softness of the substrate is crucial for the observation of the odd-even effect in LbL assemblies. The results evidenced that additional effects, as e.g. the surface tension of the terminating layer, are negligible for the odd-even effect on soft substrates.