Small-angle neutron scattering of D2O–C12E5 mixtures and microemulsions with <i>n</i>-octane: Direct analysis by Fourier transformation

Strey, R.; Glatter, Otto; Schubert, K. V.; Kaler, Eric W.

doi:10.1063/1.471960

Cited by 102 publications

(116 citation statements)

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“…The peak is predicted to appear whenever the condition φ α 2q e −2ǫ 3 /T is satisfied. The peaked structure factor is a distinctive characteristic of bicontinuous microemulsions, as borne out by many experimental studies [5,43]. It is important to emphasize, that our model predicts that the peak occurs only when φ > max[ 1 2 , φ b ] which means that, in principle there may be network microemulsions that do not show a peak in the structure factor ( the region between the percolation line and vertical φ = 1/2 line Fig.…”

Section: Microemulsionsmentioning

confidence: 56%

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Thermodynamics and structure of self-assembled networks

2002

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We study a generic model of self-assembling chains which can branch and form networks with branching points (junctions) of arbitrary functionality. The physical realizations include physical gels, wormlike micells, dipolar fluids and microemulsions. The model maps the partition function of a solution of branched, self-assembling, mutually avoiding clusters onto that of a Heisenberg magnet in the mathematical limit of zero spin components. Regarding thermodynamics properties as well as scattering strucuture factor, the mapping accounts rigorously for all possible cluster configuration, except for closed rings. The model is solved in the mean field approximation. It is found that despite the absence of any specific interaction between the chains, the presence of the junctions induces an effective attraction between the monomers, which in the case of three-fold junctions leads to a first order reentrant phase separation between a dilute phase consisting mainly of single chains, and a dense network, or two network phases. The model is then modified in order to predict the structural properties on the mean field level. Independent of the phase separation, we predict the percolation (connectivity) transition at which an infinite network is formed. The percolation transition partially overlaps with the first-order transition. The percolation transition is a * e-mail:anton.zilman@weizmann.ac.il 1 continuous, non thermodynamic transition that describes a change in the topology of the system but not a thermodynamic phase transition. Our treatment which predicts both the thermodynamic phase equilibria as well as the spatial correlations in the system allows us to treat both the phase separation and the percolation threshold within the same framework. The density-density correlation correlation has a usual Ornstein-Zernicke form at low monomer densities. At higher densities, a peak emerges in the structure factor, signifying an onset of medium-range order in the system. Implications of the results for different physical systems are discussed.

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Section: Microemulsionsmentioning

confidence: 56%

“…In the context of microemulsions, this peak can be related to the experimentally observed peak in the scattering from bicontinuous microemulsions [5,43] (cf. Discussion).…”

Section: High Densitiesmentioning

confidence: 76%

Thermodynamics and structure of self-assembled networks

2002

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“…Ternary systems. The formation of spherical, cylindrical and lamellar structures in the ternary system water/C12Efln-octane (Cl2E5 = pentaethylene glycol mono-n-dodecyl ether) in relation to concentration and temperature was examined by SANS measurements (Strey et al, 1996). The data were evaluated using the IFT technique.…”

Section: Resultsmentioning

confidence: 99%

Direct Structure Analysis of Small-Angle Scattering Data from Polydisperse Colloidal Particles

Mittelbach¹,

Glatter²

1998

J Appl Cryst

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The internal structure of colloidal particles of spherical, rod-like or lamellar symmetry can be determined from small-angle scattering data by means of the well established 'indirect Fourier transformation' technique followed by the numerical deconvolution of the pair distance distribution function. The method works without any preliminary knowledge of the particles under investigation except a rough estimate of their maximal size. However, its use has hitherto been restricted to monodisperse or very weakly polydisperse systems. In this paper a new method is presented that is capable of determining the radial scattering length density distribution of particles in strongly polydisperse samples and provides a parameter that quantifies the degree of polydispersity present in the system. The only additional information necessary is the function type which describes the size distribution of the particles under investigation in the best way possible. However, the method is limited to polydisperse systems which may be characterized by only one linear size parameter. In addition, it is now possible to represent the density profile by smooth spline functions, i.e. the technique is no longer restricted to step functions as basis functions. The mathematical procedure is outlined in detail and numerical results of simulations as well as of experimental data from small-angle neutron scattering and small-angle X-ray scattering measurements of surfactant aggregates in water and water/oil systems are given.

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“…92,157,158,159,160,161 Microemulsions are far away from ideal diluted solutions as the surfactant concentration is very high. In most cases SAS spectra of microemulsions exhibit a single broad scattering peak.…”

Section: 156mentioning

confidence: 99%