Size distributions of platinum nanoparticles embedded in nanostructured hybrid matrixes and the internal structure of these systems were studied by anomalous and conventional small-angle X-ray scattering. The complexes of polyelectrolyte gels with oppositely charged surfactants were employed as nanostructured matrixes. Two complexes of a cationic gel of poly(diallyldimethylammonium chloride) with anionic surfactants sodium dodecyl sulfate and sodium dodecylbenzene sulfonate were charged with platinum compounds (PtCl 4 , Na 2 PtCl 6 , (NH 4 ) 2 PtCl 4 , and H 2 PtCl 6 ) and reduced with NaBH 4 and N 2 H 4 ×H 2 O. Fast reduction with NaBH 4 yields mostly small Pt nanoparticles with radii about 2 to 3 nm, whereas for N 2 H 4 ×H 2 O, a significant amount of large (up to 40 nm) particles is found. The pH of the reaction medium and the Pt ion geometry were found to influence particle nucleation and growth. The internal ordering in gel/surfactant complexes during the nanoparticle formation was characterized from the Bragg peaks in the scattering patterns. Although the magnitude of the peaks diminishes after metal nanoparticle formation, quantitative peak parameters indicate an increase of the degree of order. This suggests that the highly ordered zones in the hydrogels concentrate around the growing nanoparticles thus stabilizing them. Addition of Na 2 PtCl 6 to another complex, an anionic gel of poly(methacrylic acid) with a cationic surfactant cetylpyridinium chloride, results in drastic structure rearrangements. The order observed in the collapsed gel nearly degrades due to a competitive interaction of the negative PtCl 6 2ions with positively charged pyridinium heads and a new micellar-like structure is formed instead. Further Pt ion reduction restores the initial gel structure and yields very large (radii up to 80 nm) metal particles growing outside the areas of the surfactant ordering.

Complexes of polyelectrolyte gels with oppositely charged surfactants form ordered polymer matrices with unique structure properties, which can be used in a wide range of medical, chemical and physical applications. Ordered matrices made of natural components are of special interest for medical and biological purposes. In the present study, self‐organised complexes of native ι‐ and κ‐carrageenans formed with oppositely charged cetylpyridinium chloride (CPC) are prepared and structurally characterised using small‐angle X‐ray scattering (SAXS). Starting from the molar ratio CPC/(charge of carrrageenan) of 0.2, the carrageenan gel shrinks and ordered motifs in its internal structure are formed. The internal order in the sample is reflected by the Bragg peaks in the scattering patterns which permit to compute periodicity and characteristic sizes of the ordered regions. Moreover, strong central scattering appears and the calculated fractal dimensions indicate that these regions are organised in well defined clusters. The periodicity of the ordered motifs computed from the Bragg peaks in the scattering patterns corresponds to the width of the surfactant bilayer (about 4.0 nm) for all the complexes. The crystallite size ranges from 25 nm to 40 nm depending on the type of carrageenan and on the amount of CPC. A model of the ordered fragments is proposed whereby the carrageenan/surfactant bilayers are regularly packed at the walls of hollow cylindric clusters with the outer radius of about 8 nm and height 40 nm. More detailed ab initio models indicate that these particles are formed by bent worm‐like substructures with the cross‐section coinciding to the thickness of the carrageenan/CPC bilayer. Thanks to a higher charge density per monomer, ι‐carrageenans form more regular structures than κ‐carrageenans.

The optical, X-ray-and AFM-properties of the particles of cholesteric liquid-crystalline dispersion (CLCD) formed by double-stranded DNA molecules and treated with gadolinium salts are studied. It is shown that under certain conditions this treatment results in two effects: i)amplification of the abnormal negative band in the CD spectra specific to the initial CLCD, and ii) disappearance of small-angle X-ray scattering specific of ordered DNA molecules. The explanation of these effects is based on a suggestion that gadolinium ions when present at high concentrations not only induce nano-scale changes in the DNA secondary structure, but also overcompensate the DNA negative charges, influencing the efficiency of DNA-DNA interactions in the content of the particles of CLCD. These processes lead to transformation of the spatial structure in particles of CLCD. The resulting structure of particles of DNA CLCD highly enriched in gadolinium is not "liquid-crystalline"; rather it is a rigid construction of practical importance.