Liquid Crystal Main Chain Polymers

Fig. 33. Examples of main-chain polymer liquid crystals I - mesogenic group, II - spacer.

Deuterium NMR measurements are performed for main-chain polymer liquid crystals having structures such as-[Ph-0-C0-Ph-O-(CH2)n-0-Ph-C0-O-Ph-0-(CH2)n-0lx- with n = 9 and 10. The general profiles of the spectra are found to be similar to those of the corresponding dimer. The results of the RIS analysis suggest that the spatial configurations of the spacer are nearly identical between the dimer and the polymer. 

In main-chain polymer liquid crystals (MCPLC), the rigid mesogenic units are inserted into the chain, along with some more flexible spacers that allow the attainment of the liquid-crystalline degree of order. 

TABLE 5.3 Chemical Constitution Typical of Thermotropic Main-Chain-Polymer Liquid Crystals, i.e., [4]... 

Group Arrangements Typical of Thermotropic Main-Chain Polymer Liquid Crystals... 

Abe, A., and Furuya, H., Orientational characteristics of main-chain polymer liquid crystals as revealed by the rotational isomeric state analysis of deuterium NMR spectra, Macro-molecules, 22, 2982-2987. (1989). 

Extensive structure analyses were first carried out for the dimers depicted in Scheme 1 (CBA- , n = 9,10). The same techniques were applied to the main-chain polymer liquid crystals having analogous chain sequences (Scheme 2), leading to the conclusion that conformational characteristics of the spacer involved in the nematic state are essentially the same in both dimer and polymer liquid crystals [99]. The molecular scheme described previously has also been successf ully adopted in the analysis of the observed chemical shift and the dipolar coupling data of the dimer and trimer com-... 

In the following, attention is focused only on some results obtained for solutions of thermotropic PLCs, and particularly on those of side group polymer liquid crystals (SGPLCs) since main chain polymer liquid crystals (MCPLCs) are normally difficult to dissolve and at least are insoluble in non-protonated solvents. The inclusion of lyotropic systems would be beyond the scope of this chapter and also would give no contribution to solving the question of how the properties of solutions of PLCs differ from those of non-LC polymers with similar molecular design. 

ELASTIC MODULI OF THERMOTROPIC MAIN CHAIN POLYMER LIQUID CRYSTALS... 

Main-chain polymer liquid-crystal (MCLCP)... 

Fig. 13.2 Main chain polymer liquid crystal phases (a) nematic, (b) smectic (Collins 2005) [Reproduced with permission from Wiley VCH Verlag GmBH Co]...

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