Conformation of the spacer

While the rate of an electron-transfer process and thus the mode of the resulting spin-density distribution can be controlled by the length and the conformation of the spacer groups, the ion pairing creates an additional factor that can serve as some external control even for a given choice of subunits and spacers. 

The conformation of the spacer can be estimated by using samples carrying a per-deuterated n-alkane sequence. The following expression may be adopted for the deuterium quadrupolar splittings (Avi) due to the ith methylene unit ... 

FIGURE 7.12 Schematic representation of the nematic arrangement of main-chain LCs. While the orientational fluctuation of the entire molecule varies as a function of temperature, the nematic conformation of the spacer remains quite stable over the entire LC region defined by the two phase houndaries (7cn and Tni). 

Before closing Section 7.3 we would like to mention briefly the optical anisotropy of the nematic conformation of the spacer. The parameter A, representing the strength of the anisotropic interaction in theMaier-Saupe theory [Eq. (7.1)], should be related... 

PVT analysis presented in this chapter has revealed that main-chain LCs resemble monomer LCs in many thermodynamic characteristics. In addition to the conventional anisotropic dispersion interactions and steric repulsions, however, special attention is required for the effect of the nematic conformation of the spacer on the molecular... 

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]. 

Keywords Conformation of the spacer Nematic conformation Odd-even effect <... 

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