SANS studies

Wu, G Chu, B Schneider, DK, SANS Study of the Micellar Strucmre of PEO/PPO/PEO Aqueous Solutions, Journal of Physical Chemistry 99, 5094, 1995. 

We will limit ourselves to reviewing recent SAXS and SANS studies of putatively fully unfolded states formed at equilibrium. We direct readers interested in partially folded states (kinetic and equilibrium molten globules and their brethren) to a number of excellent recent articles and reviews (Kataoka and Goto, 1996 Kataoka et al., 1997 Uversky etal., 1998 Pollack et al., 1999 Doniach, 2001). Similarly, we will not discuss in detail the technical aspects of scattering studies or the precise interpretation of scattering profiles, but instead direct the reader to the appropriate resources (Glatter and Kratky, 1982 Doniach et al., 1995 Kataoka and Goto, 1996 Doniach, 2001). 

SANS study of the mechanisms and kinetics of the synthesis of mesoporous materials from micelles of tri-block copolymers... 

In this paper, we report about a recent in situ SANS study of the synthesis of the SBA-15 materials [5]. Our results demonstrate that SANS (using D20 instead of H20 as a solvent) is a powerful tool for the determination of size and shape of hybrid inorganic-organic micelles during the first synthesis step when the precursor species undergo hydrolysis and form an inorganic framework around the copolymer micelles. 

Wang H, Christopherson GT, Xu ZY, Porcar L, Ho DL, Fry D, Hobbie EK (2005). Shear-SANS study of single-walled carbon nanotube suspensions.Chem. Phys. Lett. 416 182-186. 

The solvent is usually treated as an incompressible continuum. However, it must be kept in mind that SAXS- or SANS-studies in solution only probe the difference between the scattering length density of the dissolved object and the solvent. Hence, the scattering intensity is determined by the contrast between solute and solvent. This contrast may fluctuate too because of the density fluctuations of the solvent and there is a small but non-zero contribution to I (q), even at vanishing contrast. 

A more recent SANS study revealed a 4% increase in dendrimer volume with decreasing pH (Chen et al. 2007). Although these stmctural variations were significantly less than predicted by the MD studies, this study confirmed the occurrence of both counterion condensation and water penetration of the dendrimer interior. 

Jenkins, P. J., Donald, A. M. (1998). Gelatinisation of starch a combined SAXS/WAXS/DSC and SANS study. Carbohydrate Research, 308, 133-147. 

K. C. Littrell. Sans study of third phase formation in the Th(IV)-HN03/TBP-n-octane system. Sep. Sci. TechnoL, 38(12-13) 3333-3351, 2003. 

The dendrimer type with a stilbene scaffold and long-chain end groups mentioned in Section 4.1.5.3 was shown to have a disc-like flattened molecular shape in solution by SAXS and SANS studies performed by Ballauff et al. [51]. 

For quite some time, there have been indications for a phase-separation in the shell of polyelectrolyte block copolymer micelles. Electrophoretic mobility measurements on PS-PMAc [50] indicated that a part of the shell exhibits a considerable higher ionic strength than the surrounding medium. This had been corroborated by fluorescence studies on PS-PMAc [51-53] and PS-P2VP-heteroarm star polymers [54]. According to the steady-state fluorescence and anisotropy decays of fluorophores attached to the ends of the PMAc-blocks, a certain fraction of the fluorophores (probably those on the blocks that were folded back to the core/shell interface) monitored a lower polarity of the environment. Their mobility was substantially restricted. It thus seemed as if the polyelectrolyte corona was phase separated into a dense interior part and a dilute outer part. Further experimental evidence for the existence of a dense interior corona domain has been found in an NMR/SANS-study on poly(methylmethacrylate-fr-acrylic acid) (PMMA-PAAc) micelles [55]. 

ZengXB, Ungar G, Spells SJ, King S (2004) Real-time SANS study of transient phases in polymer crystallization. Highlights of ISIS Science, Ann Rep Rutherford-Appleton Lab (in press)... 

There are several published reports on SANS studies carried out on aqueous dispersion of lipid in water. The measurement of interlamellar repeat distances within multilamellar liposomes is probably the most easily accomplished and reported type of experiment. The repeat distance measured is the length of the lipid molecule plus that of the water layer that separates the hydrophobic layers of the liposome (Fig. 2). This distance has been determined using the technique for several different lipid/water multilamellar systems. For example, the interlamellar repeat distance for multilamellar liposomes of DPPC has been measured by several workers as approximately 60 A (Winter and Pilgrim, 1989 Martel and Ahmed, 1990 Watkinson et al., 1991). Figure 3 depicts typical SANS data for DPPC at different concentrations in D2O and shows clear Bragg peaks at Q s 0.1, corresponding to an interlamellar repeat distance... 

---