Interaction of polystyrene-block-poly(methacrylic acid) micelles (PS-PMAA) with cationic surfactant N-dodecylpyridinium chloride (DPCl) in alkaline aqueous solutions was studied by static and dynamic light scattering, SAXS, cryogenic transmission electron microscopy (cryo-TEM), isothermal titration calorimetry (ITC), and time-resolved fluorescence spectroscopy. ITC and fluorescence measurements show that there are two distinct regimes of surfactant binding in the micellar corona (depending on the DPCl content) caused by different interactions of DPCl with PMAA in the inner and outer parts of the corona. The compensation of the negative charge of the micellar corona by DPCl leads to the aggregation of PS-PMAA micelles, and the micelles form colloidal aggregates at a certain critical surfactant concentration. SAXS shows that the aggregates are formed by individual PS-PMAA micelles with intact cores and collapsed coronas interconnected with surfactant micelles by electrostatic interactions. Unlike polyelectrolyte-surfactant complexes formed by free polyelectrolyte chains, the PMAA/DPCl complex with collapsed corona does not contain surfactant micelles.

The formation of complexes between the cationic polyelectrolyte poly[3,5-bis(dimethylaminomethylene)hydroxystyrene] (Q-N-PHOS), bearing two cationic sites per repeating unit, and DNA molecules in aqueous solutions is investigated at pH 7 and at various salt (NaCl) concentrations and DNA/polymer ratios. The structural characteristics of the polyplexes at different DNA/polymer ratios were characterized in terms of mass, size, and charge using static, dynamic, and electrophoretic light scattering and fluorescence spectroscopy. The results indicate that the complexes have a loose spherical morphology with size in the range of 45-100 nm depending on polymer to DNA ratio and ionic strength of the solution. Most interestingly, it is found that the polyplexes' response to changes in the ionic strength of the surrounding solution after complexation depends strongly on the initial solution ionic strength during complex formation. This also points to differences in the nanostructures of polyplexes formed at different ionic strengths.

The electrostatic coassembly of a double hydrophilic block copolymer poly­(2-vinylpyridine)-block-poly­(ethylene oxide) (P2VP–PEO) with the gemini surfactant 6,6′-(ethane-1,2-diylbis­(oxy))­bis­(sodium 3-dodecyl benzenesulfonate) (G2) was studied in acidic aqueous solutions by a combination of light scattering, SANS, Cryo-TEM, and ITC. As the critical micelle concentration of gemini surfactants is ∼102 times lower than that of analogous single-tail surfactants, polyelectrolyte chains interact with G2 vesicles instead of individual G2 molecules. The study shows that hydrophobicity, bulkiness, and stiffness of G2 domains formed upon its binding to the P2VP chain affect the coassembly and formation of nanoparticles. The study allows for presentation of a comprehensive outline of the coassembling process and elucidating the structure of the formed nanoparticles.