Intercalated smectic mesophase

Note 1 The recommended subscript to designate an intercalated smectic mesophase is c Note 2 Intercalated smectic mesophases are commonly observed for liquid-crystal dimers. Note 3 At present intercalated smectic A (SmAc) and smectic C (SmCc) as well as intercalated crystal B (Be), G (Gc) and J (L) mesophases have been observed. 

Note 4 The local structure in the nematic mesophase of certain dimers exhibit an intercalated smectic mesophase. 

Asymmetric dimeric liquid crystals with charge-transfer groups constitute good models for the mesomorphic self-organization of the related polymers discussed above. Their mesophase structures have been studied in some detail [34]. In this context, the formation of intercalated smectic phases of the A, C, and I type is especially noteworthy [34c]. However, the nature of the specific interactions between the unlike mesogenic groups, as well as the conformation of the spacer, are still to be explained [34d]. 

Examples of rod-like molecules with a branched fluorinated chain at one end (compounds 90-93) are collated in Fig. 26 [166]. It is interesting that smectic phases are retained despite the significant size of these chains. This is mainly a result of the intercalation of the aromatic cores and aliphatic spacers of these molecules, which can compensate this steric distortion. These branched chains remove the B and E phases with crystalline layers and replace them by fluid smectic phases, including SmC phases. The comparison in this figure also shows that the bulky and flexible bis(perfluoropropylene oxide) derived chains (compounds 92, 93) can provide LC materials with especially low melting points and broad mesophase ranges due to the higher conformational flexibility of perfluoroethers compared to linear perfluoroalkyl chains [99, 176]. 

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