Small-angle electron scattering

The polymer concentration profile has been measured by small-angle neutron scattering from polymers adsorbed onto colloidal particles [70,71] or porous media [72] and from flat surfaces with neutron reflectivity [73] and optical reflectometry [74]. The fraction of segments bound to the solid surface is nicely revealed in NMR studies [75], infrared spectroscopy [76], and electron spin resonance [77]. An example of the concentration profile obtained by inverting neutron scattering measurements appears in Fig. XI-7, showing a typical surface volume fraction of 0.25 and layer thickness of 10-15 nm. The profile decays rapidly and monotonically but does not exhibit power-law scaling [70]. 

Dudarev, S.L., Peng, L.-M. and Whelan, M.J. (1992). On the damping of coherence in the small-angle inelastic scattering of high-energy electrons by crystals, Phys. Letts. A, 170, 111-115. 

Characterization of Dendritically Branched Polymers by Small Angle Neutron Scattering (SANS), Small Angle X-Ray Scattering (SAXS) and Transmission Electron Microscopy (TEM)... 

Small angle X-ray scattering monitoring the distribution of electron density has been used to probe resin morphology [109]. More recently contrast matched small angle neutron scattering has also been employed [110, 111]. These techniques can also be applied to wet resins and tend to probe the very low dimensions of the polymer matrix structure. More studies are needed to identify the real value of these approaches. 

Further characterization of the mechanical properties and structures of such zeolite-reinforced PDMS elastomers by Wen and Mark [139] also utilized small-angle neutron scattering (SANS) [141, 143, 214—220] and transmission electron microscopy (TEM). The neutron-scattering profiles of the pure and zeolite-filled PDMS networks were identical, which indicated negligible penetration of the polymer into the zeolite pores. The TEM pictures showed that the zeolite with the larger pore size had a somewhat smaller particle size, and this is probably the origin of its superior reinforcing properties [62, 139]. 

Small-angle neutron scattering (SANS) can be applied to food systems to obtain information on intra- and inter-particle structure, on a length scale of typically 10-1000 A. The systems studied are usually disordered, and so only a limited number of parameters can be determined. Some model systems (e.g., certain microemulsions) are characterized by only a limited number of parameters, and so SANS can describe them fully without complementary techniques. Food systems, however, are often disordered, polydisperse and complex. For these systems, SANS is rarely used alone. Instead, it is used to study systems that have already been well characterized by other methods, viz., light scattering, electron microscopy, NMR, fluorescence, etc. SANS data can then be used to test alternative models, or to derive quantitative parameters for an existing qualitative model. 

It is not possible to discuss all the methods available for characterizing foods critically and systematically in a single volume. Methods pertaining to interfaces (food emulsions, foams, and dispersions), fluorescence, ultrasonics, nuclear magnetic resonance, electron spin resonance, Fourier-transform infrared and near infrared spectroscopy, small-angle neutron scattering, dielectrics, microscopy, rheology, sensors, antibodies, flavor and aroma analysis are included. 

Holland, H.E., et al. 1995. Interactions between liposomes and human stratum corneum in vitro Freeze fracture electron microscopical visualization and small angle diffraction scattering studies. Br J Dermatol 132 853. 

M. A. Bolzinger-Thevenin, I. L. Grossiord, and M. C. Poelman, Characterization of a sucrose ester microemulsion by freeze fracture electron micrograph and small angle neutron scattering experiments, Langmuir, 15 (1999) 2307-2315. 

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