An overview of an important aspect of SANS research on charged colloidal suspensions is presented. These systems are characterized by pronounced interparticle correlations resulting from a strong and long-range double-layer interaction between macroions (i.e. the charged colloidal particles). Emphasis is laid on the use of simple statistical mechanical models, which are applicable in treating SANS data, that take into account the double-layer interaction. Examples are taken from work on dense protein solutions, ionic micellar solutions and protein-detergent complexes in aqueous solutions. Spherical and rod-like particles are considered. Polydispersity effects are taken into account whenever possible. In the case of rod-like systems, alignment by a shear gradient and the consequent analysis of two-dimensional SANS intensity distributions are briefly discussed.

Rod-like micelles of hexadecylpyridiniumsalicylate in aqueous solution were aligned by a shear gradient Γ of up to 40 s−1. Small angle neutron diffraction patterns of a solution of 20 mM/ℓ show a pronounced peak in scattering intensity at a momentum transfer of 0.15 nm−1 due to a correlation of the charged micelles. This correlation peak becomes deformed substantially with increasing Γ. A simple model is presented, taking into account an anisotropic change of the pair correlation function. It turns out that the order is reduced in the direction of the vector of velocity v of the sheared liquid and increases perpendicular to this vector.

The article presents kinetic data on micellar systems that were obtained with relaxation techniques. Problems that are relevant to the following topics are discussed in detail:1. Differences in the dynamic behaviour of micellar systems consisting of single-and double chain detergents. 2. The dynamics of micellar systems consisting of ionic detergents with hydrophobic counterions. 3. The dynamic behavior of micellar systems of perfluorated ionic detergents.For most of the systems two relaxation times could be observed which very often showed characteristic differences in their temperature and concentration dependence. The two relaxation processes were associated according to the theory of micelle formation by G. Aniansson and S. Wall to the shift of the micellar distribution curve and the change of the micelle concentration. The following parameters were evaluated from the data: The residence times of the detergent molecules inside the micelles, the mean aggregation number of the micelles, the width of the micellar distribution curves and the concentrations of the micellar nuclei and their aggregation numbers. Ber. Bunsenges. Phys. Chem. 82,988-1001 (1978) -0 Verlag Chemie, D-6940 Weinheim, 1978. 1. Die Unterschiede im dynamischen Verhalten von Mizellgleichgewichten bei ein-und zweikettigen Tensiden. 2. Das dynamische Verhalten von Mizellen aus ionogenen Tensiden mit hydrophoben Gegenionen. 3. Das dynamische Verhalten von Mizellen aus perfluorierten Tensiden. Bei den meisten Systemen konnten zwei Relaxationszeiten beobachtet werden, die fur die verschiedenen Systeme oft charakteristische Unterschiede in der Temperatur-und Konzentrationsabhangigkeit aufweisen. Die beiden Relaxationsprozesse wurden nach der Theorie der Mizellbildung von G. Aniansson und S. Wall der Verschiebung der Mizellverteilungskurve bei konstanter Mizellkonzentration und der Anderung der Mizellkonzentration zugeordnet. Aus den Relaxationszeiten wurden die Verweiizeiten der Tensidmolekiile in der Mizelle, die mittleren Aggregationszahlen der Mizellen, die Breite der Verteilungskurven und die Konzentration der Mizellkeime sowie deren Aggregationszahlen ermittelt. 9 -8t -6 'In Y ; $ 5m D -4 - -

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ABSTRACT:The interactions of hydrophobically modified polyelectrolytes poly(acrylamide-sodium acrylic acid-N-(4-butyl)phenylacrylamide [P(AM-AA-BPAM)] with anionic (sodium dodecyl sulfate), cationic (cetyl trimethylammonium bromide), and nonionic (tetradecyldimethylaminoxid) surfactants were studied via solution rheology, surface tension, and atomic force microscopy measurements. Viscosity measurements indicated that the intermolecular association of the polymer was greatly enhanced by the interaction with the surfactants, especially the oppositely charged surfactants with both a hydrophobic association and an electrostatic attraction. The greatest viscosity increase was realized with the addition of such oppositely charged surfactants.

The refractive index of several perfluorinated surfactant solutions was measured as a function of the concentration. The plot of the refractive index against the concentration for each surfactant shows a sharp break at the cmc. For several systems the slope of the refractive index changed even its sign. The extent of this change is much bigger for perfluorinated surfactants than the change that is shown by hydrocarbon surfactants. It is shown by density measurements that the difference of the refractive index increment above and below the cmc is due to the difference of the partial molar volumes of the surfactant molecules in the monomer and in the micellar state. It is thus possible to determine volume changes in surfactant systems by means of the measurement of the refractive index.

Sodium vapor was released in darkness on the downleg of a rocket trajectory, from 150 to 125 km. An intense headglow was observed surrounding the rocket, followed by a short‐lived afterglow disappearing within 0.2–0.5 s. The glow is interpreted in terms of a chemiluminous reaction involving sodium dimers Na2. The dimers react with atomic oxygen either in a single step, Na2 + O → Na* + NaO, or in two steps, Na2 + O → Na + NaO and NaO + O → Na* + O2, with an effective bimolecular rate constant of 6 × 10−11 cm³ s−1. The Na2‐O reaction could be involved in the natural sodium nightglow, but it is difficult to explain the required fast resupply of dimers from monomers.