Linear, Taper-Shaped, and Dendritic Molecules with RF-Chains

3 Linear, Taper-Shaped, and Dendritic Molecules with RF-Chains 

Beside these compounds which combine alkyl chains and perfluorinated chains at opposite ends of a cyclic unit, there are several examples of liquid crystalline materials combining a single aromatic ring with a single semiperfluorinated alkyl chain or with two or three Rp-chains in close proximity. 

1 Smectic Phases of Liquid Crystals with One Aromatic Ring and One RP-Chain 

For these compounds the packing of the molecules also depends strongly on the details of the molecular structure (see Fig. 9) and on the delicate balance between segregation and optimized space filling. For example, for the SmA phases of the 4-substituted ethers 15b (4-N02) and 16b (4-CN) the dll ratio is around 1.7 and an antiparallel partial bilayer arrangement with interdigitated aromatics was proposed (see Fig. lib) [113]. However, for the SmA phases of the 1,3-substituted ethers 15a 

The same study has shown that the organization completely changes for the corresponding benzoic acid 23 (Fig. 10) where the COOH groups form cyclic dimers with a linear shape.10 In this case there is no interdigitation of the Rp-chains and a (tilted) double layer structure is formed (see Fig. 11c), which is in line with the dll ratio of 1.6-1.7 observed for these benzoic acids. Related types of LC structures have been discussed for other partly fluorinated 4-alkoxybenzoic acids [126], and succinimidyl benzoates 24 [121]. 

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