Scattering neutron reflectivity

The ability to contrast match the air with a mixture of water and heavy water makes neutron reflectivity an attractive technique [180,181], Under these contrast conditions the scattering arises from the monolayer alone and combining... 

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]. 

Fig. XV-4. Schematic drawing of four streptavidin molecules bound to biotinylated lipid in a monolayer above heavy water. The scattering length density for neutron reflectivity is shown at the side. (From Ref. 30.)...

Figure 16-15. Time-dependent intensity profile of the (200) reflection of (AgBr + NaBr) mixtures measured during interdiffusion at 621 K. Wavelength of the scattered neutrons Xn = 2.36 A (after [G. Eckold (1992)]).

Thin films of block copolymer melts, and block copolymers adsorbed at the liquid-liquid interface, have been investigated using specular reflectivity (largely neutron reflectivity due to the ability to vary the scattering contrast). Off-specular reflection is, in principle, a powerful method for determining in-plane structure in block copolymer films but is not yet widely used. 

Fig. 2.54 Neutron reflectivity profile for a symmetric PS-dPMMA diblock (Mw 30 kg moP1) as a function of incident wavevector (Russell 1990). The inset shows the scattering length density (b/V, the neutron scattering length per unit volume) profile normal to the film surface that was used to calculate the reflectivity profile shown as the solid line, This is typical of a block copolymer film containing a multilayer stack, with lamellae parallel to the surface.

Fig. 2.59 Neutron reflectivity profiles for a PS-riPMMA symmetric diblock copolymer (Mw = 29.7kgmor ) film of total thickness 5232 A (Menelle et al. 1992). Experiments were performed on samples annealed at the temperatures shown. The solid lines were computed using the scattering length density profiles shown in the insets, which show that the surface induces lamellar order even above the bulk ODT 157 8°C (the air-polymer interface is located at z - 0). 

Figure 6. Polarized neutron reflectivities of fN 0 = 5 nm, 20 nm and 60 nm samples during the reversal process. The spin flip (R+, R +) and non spin flip (if4-1", R") reflectivities are simultaneously modeled to obtain the magnetization configuration as shown in the inset. The lines are the computed reflectivities for different scattering cross-sections based on this model.

Penfold, J. (1991). Data interpretation in specular neutron reflection, in Neutron, X-Ray and Light Scattering, P. Lindner and T. Zemb (Eds), Elsevier, New York, p. 223-235. 

Figure 4.29 Scattering length density profiles for an [Os(bpy)2(PVP)ioCl]Cl film in (a) perchloric acid, and (b) p-toluene sulfonic acid at different pff levels. From R.W. Wilson, R. Cubitt, A. Glidle, A.R. ffillman, P.M. Saville and J.G. Vos, A neutron reflectivity study of [Os(bpy)2(PVP)ioCl]+ polymer film modified electrodes effect of pff and counterion, /. Electrochem. Soc., 145,1454-1461 (1998). Reproduced by permission of The Electrochemical Society, Inc...

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