Planar anchoring

T. Gruhn, M. Schoen. A grand canonical ensemble Monte Carlo study of confined planar and homeotropically anchored Gay-Berne films. Mol Phys 95 681-692, 1998. 

AB diblock copolymers in the presence of a selective surface can form an adsorbed layer, which is a planar form of aggregation or self-assembly. This is very useful in the manipulation of the surface properties of solid surfaces, especially those that are employed in liquid media. Several situations have been studied both theoretically and experimentally, among them the case of a selective surface but a nonselective solvent [75] which results in swelling of both the anchor and the buoy layers. However, we concentrate on the situation most closely related to the micelle conditions just discussed, namely, adsorption from a selective solvent. Our theoretical discussion is adapted and abbreviated from that of Marques et al. [76], who considered many features not discussed here. They began their analysis from the grand canonical free energy of a block copolymer layer in equilibrium with a reservoir containing soluble block copolymer at chemical potential peK. They also considered the possible effects of micellization in solution on the adsorption process [61]. We assume in this presentation that the anchor layer is in a solvent-free, melt state above Tg. The anchor layer is assumed to be thin and smooth, with a sharp interface between it and the solvent swollen buoy layer. 

The alignment of the director at the nematic free surface of real systems is not found to exhibit universal behaviour. Depending on the mesogen, homeotro-pic, tilted and planar anchoring have been observed. Clearly, to study this interface in a simulation a potential which exhibits a nematic phase in co-... 

The large and small subunits interact extensively with each other burying the catalytic site and the proximal [4Fe-4S] cluster at about 3nm from the molecular surface. It is quite remarkable that the active site and the two most buried [FeS] clusters are located close to the almost planar subunit interface. The large subunit is anchored to the small subunit by about twenty-five side chains, of which several very conserved ones interact with the proximal [4Fe-4S] cluster, pointing to the role of this cluster as a direct partner of the catalytic site. 

In 2001, Takahashi and his co-workers developed the first asymmetric ruthenium-catalyzed allylic alkylation of allylic carbonates with sodium malonates which gave the corresponding alkylated compounds with an excellent enantioselectivity (Equation (Sy)). Use of planar-chiral cyclopentadienylruthenium complexes 143 with an anchor phosphine moiety is essential to promote this asymmetric allylic alkylation efficiently. The substituents at the 4-position of the cyclopentadienyl ring play a crucial role in controlling the stereochemistry. A kinetic resolution of racemic allylic carbonates has been achieved in the same reaction system (up to 99% ee). ... 

The chiral C2-conformer 42 of a ( )-cycloalkene can transform into the enantiomeric Cf-conformer 44 through a planar Cs-conformer 43, and this rope jump racemization can be prevented by anchoring one end of the unsaturated center onto the ring by means of an extra-bridge. This bridging creates a bicyclic anti-Bredt rule compound 45, revealing that all anti-Bredt rule compounds (45) with one double bond are necessarily asymmetric (C, symmetry) and have one asymmetric carbon atom. 

Fig. 3 Principle anchoring conditions of nematic liquid crystals at nanoparticle surfaces (a) planar anchoring, and (b) vertical (or homeotropic) anchoring...

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