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A newly developed high-pressure rheometer for in situ X-ray scattering experiments is described. A commercial rheometer was modified in such a way that X-ray scattering experiments can be performed under different pressures and shear. First experiments were carried out on hyaluronan, a ubiquitous biopolymer that is important for different functions in the body such as articular joint lubrication. The data hint at a decreased electrostatic interaction at higher pressure, presumably due to the increase of the dielectric constant of water by 3% and the decrease of the free volume at 300bar., QC 20170602

The development of a dedicated small-angle X-ray scattering setup for the investigation of complex fluids at different controlled shear conditions is reported. The setup utilizes a microfluidics chip with a narrowing channel. As a consequence, a shear gradient is generated within the channel and the effect of shear rate on structure and interactions is mapped spatially. In a first experiment small-angle X-ray scattering is utilized to investigate highly concentrated protein solutions up to a shear rate of 300000 s(-1). These data demonstrate that equilibrium clusters of lysozyme are destabilized at high shear rates., QC 20160407

Self-assembly in mixtures of two single-chain cationic surfactants, with different tail lengths (CTAB and DTAB) as well as of a single-chain (DTAB) and a double-chain (DDAB) cationic surfactant, with identical tail lengths, have been investigated with small-angle neutron scattering (SANS) and rationalised in terms of bending elasticity properties. The growth behaviour of micelles with respect to surfactant composition appears completely different in the two surfactant mixtures. DTAB form small oblate spheroidal micelles in presence of [NaBr]. =. 0.1. M that transform into prolate spheroidal mixed CTAB/DTAB micelles upon adding moderate amounts of CTAB, so as to give a mole fraction . y=. 0.20 in solution. Most unexpectedly, upon further addition of CTAB the mixed CTAB/DTAB micelles grow with an almost equal rate in both length and width directions to form tablets. In contrast to this behaviour, mixed DDAB/DTAB micelles grow virtually exclusively in the length direction, in presence of [NaBr]. =. 0.1. M, to form elongated ellipsoidal (tablet-shaped) and subsequently long wormlike micelles as the fraction of DDAB in the micelles increases. Mixed DDAB/DTAB micelles grow to become as long as 2000. å before an abrupt transition to large bilayer structures occurs. This means that the micelles are much longer at the micelle-to-bilayer transition as compared to the same mixture in absence of added salt. It is found that the point of transition from micelles to bilayers is significantly shifted towards higher fractions of aggregated DTAB as an appreciable amount of salt is added to DDAB/DTAB mixtures, indicating a considerable reduction of the spontaneous curvature with an increasing [NaBr]. By means of deducing the various bending elasticity constants from our experimental results, according to a novel approach by ours, we are able to conclude that the different growth behaviours appear as a consequence of a considerably lower bending rigidity, as well as higher saddle-spl, QC 20120807

Anti-Invar effect was revealed in the fcc Fe-25.3%Ni-0.73%C (wt%) alloy, which demonstrates high values of thermal expansion coefficient (TEC) (15-21) x 10(-6) K(-1) accompanied by almost temperature-insensitive behavior in temperature range of 122-525 K. Alloying with carbon considerably expanded the low temperature range of anti-Invar behavior in fcc Fe-Ni-based alloy. The Curie temperature of the alloy T(C) = 195 K was determined on measurements of temperature dependences of magnetic susceptibility and saturation magnetization. The Mossbauer and small-angle neutron scattering (SANS) experiments on the fcc Fe-25.3%Ni-(0.73-0.78)%C alloys with the varying temperatures below and above the Curie point and in external magnetic field of 1.5-5 T were conducted. Low value of the Debye temperature Theta(D) = 180 K was estimated using the temperature dependence of the integral intensity of Mossbauer spectra for specified temperature range. The inequality B(eff) = (0.7-0.9)B(ext) was obtained in external field Mossbauer measurement that points to antiferromagnetically coupled Fe atoms, which have a tendency to align their spins perpendicular to B(ext). Nano length scale magnetic in homogeneities nearby and far above T(C) were revealed, which assumed that it is caused by mixed antiferromagnetically and ferromagnetically coupled Fe atom spins. The anti-Invar behavior of Fe-Ni-C alloy is explained in terms of evolution of magnetic order with changing temperature resulting from thermally varied interspin interaction and decreasing stiffness of interatomic bond.

The association between a highly branched polyelectrolyte with ionizable groups, polyethylene imine (PEI), and an anionic surfactant, sodium dodecyl sulfate (SDS), has been investigated at two pH values, using small-angle neutron and light scattering. The scattering data allow us to obtain a detailed picture of the association structures formed. Small-angle neutron scattering (SANS) measurements in solutions containing highly charged PEI at low pH and low SDS concentrations indicate the presence of disklike aggregates. The aggregates change to a more complex three-dimensional structure with increasing surfactant concentration. One pronounced feature in the scattering curves is the presence of a Bragg-like peak at high q-values observed at a surfactant concentration of 4.2 mM and above. This scattering feature is attributed to the formation of a common well-ordered PEI/SDS structure, in analogue to what has been reported for other polyelectrolyte-surfactant systems. Precipitation occurred at the charge neutralization point, and X-ray diffraction measurements on the precipitate confirmed the existence of an ordered structure within the PEI/SDS aggregates, which was identified as a lamellar internal organization. Polyethylene imine has a low charge density in alkaline solutions. At pH 10.1 and under conditions where the surfactant was contrast matched, the SANS scattering curves showed only small changes with increasing surfactant concentration. This suggests that the polymer acts as a template onto which the surfactant molecules aggregate. Data from both static light scattering and SANS recorded under conditions where SDS and to a lower degree PEI contribute to the scattering were found to be consistent with a structure of stacked elliptic bilayers. These structures increased in size and became more compact as the surfactant concentration was increased up to the charge neutralization point., QC 20100901

The effects of salt, temperature, and deuterium oxide on the self-aggregation of n-tetradecyl-beta-D-maltoside (C(14)G(2)) in dilute solution have been investigated by static light scattering, dynamic light scattering (DLS), small-angle neutron scattering (SANS), tensiometry, and capillary viscometry. SANS data show that the micelles can be described as relatively flexible polymer-like micelles with an elliptical cross section, at least at temperatures between 35 and 50 degreesC. The micelles grow in one dimension with increasing temperature and concentration. DLS and viscometry data suggest that the micelle size reaches a maximum at 60-70 degreesC. Comparison of DLS data in D2O and H2O shows that the micelles are larger in the former case. The effect of salt on the micelle size was found to follow the Hofmeister series. Thus, at constant salt concentration, the micelle size decreases according to the sequence SO42- > Cl (-)> NO3 > I- > SCN-, where I- and SCN- act as salting-in anions. From tensiometric data, it can be concluded that the temperature effects on micelle morphology do not correlate directly with those on unimer solubility. Rather, the temperature effect on the hydrocarbon chain conformation seems to be decisive for the micelle morphology. At constant temperature, on the other hand, the effect of salt and deuterium isotope is attributable to changes in effective headgroup area, including intermolecular interactions and water of hydration., QC 20100525

The size and shape of micelles formed in aqueous mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic sugar-based surfactant n-decyl beta-D-glucopyranoside (C(10)G) at different concentrations of added salt have been investigated with small-angle neutron and static light scattering. Rather small prolate ellipsoidal micelles form in the absence of added salt and at [NaCl] = 10 mM in D2O. The micelles grow considerably in length to large rods as the electrolyte concentration is raised to [NaCl] = 0.1 M. In excess of nonionic surfactant ([SDS]/[C(10)G] = 1:3) at [NaCl] = 0.1 M in D2O, several thousands of Angstroms long wormlike micelles are observed. Most interestingly, a conspicuously large isotope solvent effect was observed from static light scattering data according to which micelles formed at [SDS]/[C(10)G] = 1:3 and [NaCl] = 0.1 M in H2O are at least five times smaller than micelles formed in the corresponding samples in D2O., QC 20100901. Tidigare titel: A Small-Angle Neutron Scattering Study of Micelles Formed in Aqueous Mixtures of Nonionic Alkylglucoside and an Anionic Surfactant. Titel ändrad 20100901.

Mixtures of the partly fluorinated cationic surfactant HFDePC (N-(1, 1,2,2-tetrahydroperfluorodecanyl)pyridinium chloride and deuterated headgroup) with C(16)TAC, hexadecyl-trimethylammonium chloride, have been investigated using small angle neutron scattering with contrast matching. Earlier results from this system suggested that a demixing occurred, into two coexisting populations of micelles, hydrocarbon-rich and fluorocarbon-rich, respectively. The present results could be explained by one type of mixed micelles with an inhomogeneous distribution of fluorinated and hydrogenated surfactants within the micelles although a demixing cannot be definitely excluded., QC 20100525 QC 20111025

The influence of salt, temperature, and deuterium oxide on the self-aggregation of n-nonyl-beta-D-glucoside (beta-C(9)G(1)) in dilute solution has been investigated by static and dynamic light scattering, neutron scattering, and tensiometry. Scattering data show that the micelles can be described as relatively stiff, elongated structures with a circular cross section. With a decrease of temperature, the micelles grow in one dimension, which makes it surprising that the critical micelle concentration (cmc) shows a concomitant increase. On the other hand, substitution of D2O for H2O causes a large increase in micelle size at low temperatures, without any appreciable effect on cmc. With increasing temperature, the deuterium effect on the micelle size diminishes. The effects of salt on the micelle size and cmc were found to follow the Hofmeister series. Thus, at constant salt concentration, the micelle size decreased according to the sequence SO42- > Cl- > Br- > NO3- > I- > SCN-, whereas the effect on cmc displays the opposite trend. Here, I- and SCN- are salting-in anions. Similarly, the effects of cations decrease with increasing polarizability in the sequence Li-divided by > Na-divided by > K-divided by > Cs-divided by. At high ionic strength, the systems separate into two micellar phases. The results imply that the size of beta-C(9)G(1) micelles is extremely sensitive to changes in the headgroup size. More specifically, temperature and salt effects on effective headgroup size, including intermolecular interactions and water of hydration, are suggested to be more decisive for the micelle morphology than the corresponding effects on unimer solubility., QC 20100525 QC 20111031