Adsorbed trilayer

Fig. 3.3. The schematic picture of the DMOAP-LC interface. The alkyl chains of DMOAP stretch perpendicularly from the surface and stabilize the adsorbed trilayer.

Fig. 3.5. The force between a 10 im glass sphere, covered with DMOAP and a DMOAP treated glass substrate in 5CB liquid crystal at two different temperatures close to TnI The solid line shows the sum of the calculated van der Waals force (dashed line) and the nematic mean field force (3.4). At zero separation the two glass surfaces are not yet in contact, due to adsorbed trilayers of liquid crystal on both surfaces that cannot be removed due to insufficient stress under the apex of the glass sphere [13],...

Fig. 3.4. The thickness of the adsorbed trilayer of the liquid crystal 5CB on DMOAP covered BK7 glass substrate. The full line is a fit to the Hertz theory with E = E/(l — v ) = 1.2 X 10 (1 0.3)Nm. R om point B to the point C, the surface adsorbed molecular trilayer is elastically deformed. At the instability point C, the layer ruptures and the AFM tip is in hard contact with the surface at D. The inset shows the linear relation between the thickness of the adsorbed layer and the length of fully extended liquid crystal molecule.

The optimized GNR-1, its bilayer and trilayer (Bernal and rhombohedral) clusters, are used as sensors of molecules. For the sake of proof-of-concept experiment, O2 and N2 are adsorbed in the surface, their small size facilitates the calculations, but this approach can be extended to any molecule (or explosive). Each cluster is optimized with the adsorbed molecule. 

Abstract Surface-induced ordering of 4-n-octyl-4 -cyanobiphenyl (8CB) near the isotropic-nematic phase transition was investigated using temperature-controlled atomic force microscopy (AIM). The glass surfaces in contact with liquid crystal were modified by an adsorbed silane surfactant, a deposited 8CB mono-layer, or a deposited 8CB trilayer. 

To obtain detailed information on the first layer, we used a sharp bare AFM tip and recorded force curves of 8CB confined between the tip and modified glass substrates. As a layer of 8CB dimers can intercalate between the alkyl chains of the DMOAP molecules the first layer is form by these intercalated dimers [26,27]. Similarly, in case of surfaces modified by a trilayer the first layer is formed by the two topmost layers of the 8CB trilayer. The elastic modulus of the first layer might be shghtly influenced by the adsorbed 8CB or DMOAP monolayer underneath. 

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