Small-angle neutron scattering experimental technique

The conformation of polymer chains in an ultra-thin film has been an attractive subject in the field of polymer physics. The chain conformation has been extensively discussed theoretically and experimentally [6-11] however, the experimental technique to study an ultra-thin film is limited because it is difficult to obtain a signal from a specimen due to the low sample volume. The conformation of polymer chains in an ultra-thin film has been examined by small angle neutron scattering (SANS), and contradictory results have been reported. With decreasing film thickness, the radius of gyration, Rg, parallel to the film plane increases when the thickness is less than the unperturbed chain dimension in the bulk state [12-14]. On the other hand, Jones et al. reported that a polystyrene chain in an ultra-thin film takes a Gaussian conformation with a similar in-plane Rg to that in the bulk state [15, 16]. 

Abstract In this chapter we discuss practical techniques and instrumentation used in experimental measurements of kinetic and equilibrium isotope effects. After describing methods to determine IE s on rate constants, brief treatments of mass spectrometry and isotope ratio mass spectrometry, NMR measurements of isotope effects, the use of radio-isotopes, techniques to determine vapor pressure and other equilibrium IE s, and IE s in small angle neutron scattering are presented. 

In order to be able to include a steric contribution in the interparticle energy calculation, an estimate of the adsorbed layer thickness is required. This is very difficult to access experimentally probably the only technique which might be able to provide an estimate is small-angle neutron scattering which was beyond the scope of this work. As a result, a theoretical estimation of the thickness was made, based on a few key observations. This is described below. 

The micelle formation process and structure can be described by thermodynamic functions (AG°mjc, AH°mjc, AS°mic), physical parameters (surface tension, conductivity, refractive index) or by using techniques such NMR spectroscopy, fluorescence spectroscopy, small-angle neutron scattering and positron annihilation. Experimental data show that the dependence of the aggregate nature, whether normal or reverse micelle is formed, depends on the dielectric constant of the medium (Das et al., 1992 Gon and Kumar, 1996 Kertes and Gutman, 1976 Ward and du Reau, 1993). The thermodynamic functions for micellization of some surfactants are presented in Table 1.1. 

At the same time, a new experimental technique, small-angle neutron scattering, was developed at the Centre d Etudes Nucleates de Saclay, and enabled numerous observations to be collected in areas which, until then, had not been accessible. 

Using ultracentrifugation and a series of advanced experimental techniques such as small-angle neutron scattering (SANS), photon correlation spectroscopy (PCS), and Si NMR, Ramsay et al. (Chapter 7) were able to smdy in detail the oxide-water interface of silica aquasols 7 to 30 nm in particle diameter and found that all the sols... 

Several different experimental techniques, such as fluorescence decay, electron spin resonance (ESR) spectroscopy, Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, neutron reflectome-try, calorimetry, Fourier-transform infrared (FT-IR) adsorption spectroscopy, small-angle neutron scattering (SANS), ellipsometry and surface force measurements, have been used to study self-assembled surfactant structures at the solid-liquid interface (11). These measurements, although providing insight into the hemimicellization process, critical aggregation numbers... 

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