![]() ![]() (c) Specular reflectivity (XRR) with α = γ and q = q z parallel to the surface normal of the slit-pore walls. At γ = 0, the momentum transfer of the scattering vector q = k f – k i points in the direction perpendicular to the surface normal (i.e., q ∥ in the x– y plane). (39) (b) In in-plane scattering geometry, the incident beam α = 0 is aligned parallel to the confining surfaces. (a) In transmission geometry, incident and scattered X-ray beams (orange) penetrate both confining slit-pore walls (gray). ![]() (38) with incident angle α, exit angle γ, in-plane angle δ, and total scattering angle 2θ. Scattering angles follow the six-circle notation by Vlieg et al. Overview of X-SFA geometries to study confined liquids by X-ray scattering. Its molecular-scale structure and orientation confined in 100 nm to 1.7 μm slit pores was studied under static and dynamic nonequilibrium conditions.įigure 2. The capability of the new device is demonstrated on the liquid crystal 4′-octyl-4-cyano-biphenyl (8CB) in its smectic A (SmA) mesophase. Relaxation processes can be studied by driving the system out of equilibrium by shear stress or compression/decompression cycles of the slit pore. The confinement gap distance is tracked simultaneously with nanometer precision by analyzing optical interference fringes of equal chromatic order. The normal load between the opposing interfaces can be modulated to study the structural dynamics of confined liquids. The in-plane structure of liquids parallel to the slit pore and density profiles perpendicular to the confining interfaces are studied by X-ray scattering and reflectivity. Complementary structural information can be obtained by simultaneous force measurements and X-ray scattering experiments. This novel device can create a precisely controlled slit-pore confinement down to dimensions on the 10 nm scale by using a cylinder-on-flat geometry for the first time. To study confined structures under dynamic conditions, we constructed an in situ X-ray surface forces apparatus (X-SFA). Thus, a detailed knowledge of the structure of confined liquids on molecular length scales is of great interest for fundamental and applied sciences. The molecular-scale structure and dynamics of confined liquids has increasingly gained relevance for applications in nanotechnology. ![]()
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