Small-angle neutron scattering determining composition

The morphological determinations have been performed by the small angle neutron scattering. It has been found that the structures mainly depend on the overall composition of the sample (the geometrical constraints). They may or may not exist, according to the temperature, but we always get lamellas for lowest water contents which turn into water-in oil globules. 

In this section we address the question of accordance between coexistence conditions determined for polymer mixtures in the bulk and confined in thin bilayer films. Macroscopic samples with the size of ca. 1 mm are analyzed by Small Angle Neutron Scattering. It probes the compositional fluctuations away from binodal to yield the effective interaction parameter %SANs(bilayer films are studied by profiling techniques to yield concentrations < q and 2 at binodal. These are described by the composition dependent interaction parameter %(([>). In fact only the section of the relation %(([>) bounded by ( q and <(>2 is relevant as it describes the whole intrinsic profile of Fig. 2. 

In the 2 region only the surface area of the droplets is preserved their volume can be adjusted so that the droplets take their optimum size i.e., a radius that locally minimizes the interfacial free energy. depends only on temperature it is independent of composition [23]. At the emulsification boundary / op( = R , whereas in the 20 region / optl < For temperatures sufficienUy below those corresponding to the micellar size and several degrees away from T, the optimum radius has been determined by small-angle neutron scattering (SANS) experiments to vary as [31]... 

The domain size in IPN s can also be determined by small-angle X-ray scattering, SAXS and small-angle neutron scattering, SANS. For IPN compositions similar to those shown in the lower right hand portion of Figure 5, SANS studies on deuterated polystyrene samples revealed chord lengths, /c, of 200-500 A for the polystyrene phase and specific surface areas, Sgp, of 122 m g"... 

As in binary surfactant-water systems considered previously, two constraints on the geometry of the surfactant interface are active a local constraint, which is due to the surfactant molecular architecture, and a global constraint, set by the composition. These constraints alone are sufficient to determine the microstructure of the microemulsion. They imply that the expected microstructure must vary continuously as a function of the composition of tile microemulsion. Calculations show - and small-angle X-ray and neutron scattering studies confirm - that the DDAB/water/alkane microemulsions consist of a complex network of water tubes within the hydrocarbon matrix. As water is added to the mixture, the Gaussian curvature - and topology -decreases [41]. Thus the connectivity of the water networks drops (Fig. 4.20). 

---