Hydrodynamic Diameter Of Aggregates Research Articles

Synthesis of Silver Nanoclusters and Nanoparticles in the Medium of Hyperbranched Polyester Polyamine, and the Morphology and Aggregation Properties of the Metal–Polymer Nanocomposite

A procedure was developed for the single-step synthesis of a metal–polymer nanocomposite based on silver nanoparticles and second-pseudogeneration superbranched polyester functionalized along the periphery with 3-[(2-aminoethyl)amino]propionate. Under the conditions of the synthesis in the medium of H2O or DMSO, hyperbranched polyester decorated with ethylenediamine moieties can act as both a reductant of the nanoscale silver state and a stabilizer of it. The synthesized composite nanomaterial is formed by aggregates of hyperbranched polyester polyamine doped with Ag(0) nanoclusters and nanoparticles of spheroidal symmetry with a face-centered cubic crystal lattice. The hydrodynamic diameter of aggregates and the diameter of particles increase with increasing molar ratioand are 34–90 and 7–14 nm, respectively.

Self-organization of oligomeric amphiphiles with pyrimidine moieties: The role of the structural factor

Supramolecular systems based on tetracationic pyrimidine-containing surfactants of acyclic and macrocyclic structures with varying nature of the spacer were studied. The critical micelle concentrations (CMC) and the hydrodynamic diameter of aggregates were determined, and the packing of molecules in the surface layer was analyzed. Insignificant differences in the CMC with variation in the nature of the spacer and in the transition from acyclic to macrocyclic surfactants suggest elimination of the structural factor in the self-organization of the investigated compounds. The molecular packing is shown to change greatly in the transition from monomeric pyrimidinophane to oligomeric tetracationic amphiphiles.

Self-assembly of poly(allylamine hydrochloride) through electrostatic interaction with sodium dodecyl sulfate

The self-assembly of poly(allylamine hydrochloride) (PAH) through an electrostatic interaction with sodium dodecyl sulfate (SDS) was explored. PAH itself showed no self-assembly in water. A light scattering study demonstrated that PAH formed monodispersed spherical aggregates in water in the presence of SDS. The hydrodynamic diameter of the aggregates was estimated to be ca. 170 nm based on the cumulant analysis. The scattering intensity and UV absorbance at 258 nm based on the aggregation increased with an increase in the molar ratio of SDS to the allylamine hydrochloride unit (SDS/AH), indicating an increase in the number of aggregates. On the other hand, the hydrodynamic diameter of aggregates was constant, i.e., independent of the SDS/AH ratio. The constant size of the aggregates in spite of the increase in the number of aggregates suggests the formation of the micellar aggregates by the intramolecular association through an electrostatic interaction.

Interactions in Aqueous Mixtures of Alkylammonium Chlorides and Sodium Cholate

The interactions of alkylammonium chlorides (the number of carbon atom per chain was either 12, 14, or 16) with sodium cholate have been investigated by a combination of techniques including light and electron microscopy, surface tension, conductivity, light scattering, and microelectrophoretic measurements. The phase behavior has strongly depended on the molar ratio and actual concentration of oppositely charged surfactants. The change in the composition of the aggregates leads to a shape transformation from globular to elongated micelles to open and/or closed bilayers (vesicles) and precipitation. The length of micelles has been found to decrease dramatically with the concentration shift to the micellar regions of either surfactant. Upon a moderate excess of one surfactant, the mean hydrodynamic diameter of aggregates increases and wormlike micelles and/or open and closed bilayers are formed. Microscopic observations of alkylammonium cholates (novel catanionic surfactants precipitated in and/or close to equimolar region) have shown the presence of a variety of morphologies including twisted ribbons, tubules and bundles of tubules.