Comprehensive Multidimensional Characterization of Polyelectrolytes and Interpolyelectrolyte Complexes in Aqueous Solutions

In this paper we give the overview of our latest results on the complexation between polyelectrolytes and oppositely charged low-molar mass species, proteins, homopolymers and block copolymers. First, we review the results on the study of the interaction of polythiophene-based polycations with phosphonium and ammonium pendants and their complexation with negatively charged multivalent species followed by fluorescence quenching. We proved that multivalent solutes bind to polyelectrolyte stronger than to previously studied polythiophene, thus, allowing for their application as luminescence sensors. Secondly, we investigated the co-assembly of polyanion with double hydrophilic block copolymer composed of polycationic block and neutral hydrophilic block and followed the complex formation by quenching of fluorescence of the indicator attached to the end of polyanion chain. We discovered that the formed interpolyelectrolyte (IPEC) core of core/shell micelles remains dynamical even after equilibrium was reached thus making such systems suitable materials for targeted delivery of multivalent species. In addition, the formation of micelles with fluid cores was observed as a result of self-assembly of di- and triblock polyelectrolytes containing a hydrophobic block with low glass transition temperature and a positively charged block. We proved their ability to encapsulate and release hydrophobic species from the soft core upon dilution. Moreover, we confirmed their ability to complex with multivalent negatively charged species. The morphology of the formed complex strongly depends on ionic strength: the aggregates formed by micelles bonded at the periphery disrupt with increasing salt concentration and a part of multivalent ions releases into solution. Finally, the multilayered nanoparticles with both soft hydrophobic and IPEC layers were designed by co-assembly between core/shell micelles with a soft core and a positively charged shell, and block polyelectrolyte composed of polyanion and neutral hydrophilic blocks. We showed that the morphology of the particles and the charge of IPEC layer of such multicompartment nanostructures can be controlled by the ratio of oppositely charged monomeric units .