Mesogen groups

Penner T L, Schiidkraut J S, Ringsdorf H and Schuster A 1991 Oriented films from polymeric amphiphiles with mesogenic groups—Langmuir-Blodgett liquid-crystals/Macromo/ecu/es 24 1041-9... 

Fig. 18. Single steps of a write/read/erase cycle for an LC side-chain polymer (134). (—), mesogenic group (0), dyestuff. transition temperature...

Properties have been determined for a series of block copolymers based on poly[3,3-bis(ethoxymethyl)oxetane] and poly [3,3-bis(methoxymethyl)oxetane]- (9-tetrahydrofuran. The block copolymers had properties suggestive of a thermoplastic elastomer (308). POX was a good main chain for a weU-developed smectic Hquid crystalline state when cyano- or fluorine-substituted biphenyls were used as mesogenic groups attached through a four-methylene spacer (309,310). Other side-chain Hquid crystalline polyoxetanes were observed with a spacer-separated azo moiety (311) and with laterally attached mesogenic groups (312). 

Figure 7 Integrated distribution curves for the angle 0 between two successive mesogenic groups calculated [14,15] for P7MB (continuous line) and P8MB (broken line).

Fig. 29. Observed and calculated 2H NMR spectra for the mesogenic groups of a) the nematic (m = 2), b) the smectic (m = 6) liquid crystalline polymer in the glassy state, showing the line shape changes due to the freezing of the jump motion of the labelled phenyl ring. The exchange frequency corresponds to the centre of the distribution of correlation times. Note that the order parameters are different, S = 0.65 in the frozen nematic, and S = 0.85 in the frozen smectic system, respectively...

In summary the results of our 2H NMR investigation illustrate the spacer model for liquid crystalline polymers, indicating, however, that the decoupling of the mesogenic groups from the main chain, while effective, is not complete. 

Mechanics of hardness indentation 137 Meso-4,5-dimethyloctane 75 Mesogenic groups 50, 52 Mesophase 149... 

Liquid crystalline main chain polymers with siloxane spacer groups were obtained by the hydrosilation of (Si—H) terminated polydimethylsiloxane oligomers and mesogenic groups with terminal double bonds as shown in Reaction Scheme XVII-(a). Reactions were usually carried out in THF with the Wacker Oil catalyst 255). Completion of the reactions was followed by the disappearance of the strong (Si—H) absorption band at 2140 cm-1 using IR spectroscopy. 

Polymers with mesogenic groups directly attached to backbone, properties, 97,98/ Polyolefin hydroperoxides and alcohols, IR bands of nitrates and nitrites, 384/ Polyolefins... 

In this category, the units giving rise to the liquid-crystalline behavior can be in the backbone (as already discussed), in the side chains, or in both [172], Of considerable interest is the orientation of the mesogenic groups and the chain backbones to which they are attached [173,174], Frequently-studied backbones include siloxanes and acrylates [175,176], but a variety of other structures have also been studied, including amphiphilics [177]. 

The side chains in these structures can rearrange into positions either parallel or perpendicular to the deformed chain backbone. [178]. The outcome depends particularly on the nature and length of the flexible spacer connecting the mesogenic groups to the chain backbone. As expected the physical properties can become strongly anisotropic [179]. 

Mesogen constituted of molecules, each with more than one mesogenic group. 

Note 1 The mesogenic groups usually have identical structures. 

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