Mesogenic side groups

Shibaev, V. P. and Plate, N. A. Thermotropic Liquid-Crystalline Polymers with Mesogenic Side Groups, Vol. 60/61, pp. 173—252. 

Figure 6. General structure for phosphazenes with mesogenic side groups. Example is a mixed substituent polymer (VII) where R represents the trifluoroethoxy group and the mesogen with flexible spacer is represented by the curlicue and rectangular box.

Disklike rc-conjugated mesogen Mesogenic side group Flexible spacer Solubilizing side chain... 

Note 5 If the mesogenic side-groups are rod-like (calamitic) in nature, the resulting polymer may, depending upon its detailed structure, exhibit any of the common types of calamitic mesophases nematic, chiral nematic or smectic. Side-on fixed SGPLC, however, are predominantly nematic or chiral nematic in character. Similarly, disc-shaped side-groups tend to promote discotic nematic or columnar mesophases while amphiphilic side-chains tend to promote amphiphilic or lyotropic mesophases. 

Note 6 A plethora of types of copolymers can be produced. For example, non-mesogenic side-groups may be used in conjunction with mesogenic side-groups and the polymer backbone may be substituted, to various degrees, with side-groups or chains. 

Note See Fig. 35. The mesogenic side-groups can be attached either as lateral substituents to the backbone mesogenic moieties that are connected to each other either (a) directly or (b) by spacers or (c) they can be attached to the spacer incorporated into the main-chain. 

Liquid crystal polymers having 1,3-dithiane or 1,3-oxathiane rings as mesogenic side groups exhibit the extremely important liquid crystal phase at around room temperature <1999MI335>. 1,3-Oxathianes have also been applied as perfumery and flavoring ingredients other derivatives exhibit excellent herbicidal activity and 1,3-oxathiane derivatives have been employed as corrosion inhibitors for steel. 

Blumstein, A. and Hsu, E. C. Liquid crystalline order in polymers with mesogenic side groups in Blumstein, A. ed. Liquid Crystalline Order in Polymers . Academic Press, New York, NY 1978, p. 105... 

Thermotropic Liquid-Crystalline Polymers with Mesogenic Side Groups... 

The article covers synthesis, structure and properties of thermotropic liquid-crystalline (LC) polymers with mesogenic side groups. Approaches towards the synthesis of such systems and the conditions for their realization in the LC state are presented, as well as the data revealing the relationship between the molecular structure of an LC polymer and the type of mesophase formed. Specific features of thermotropic LC polymers and copolymers of nematic, smectic and cholesteric types are considered. 

Thus, the remoteness of mesogenic groups from the backbone provided by a polymethylene spacer secures them sufficient autonomy from the main chain. On the other hand, the fact that mesogenic groups are chemically linked with the main chain of the macromolecule assists their cooperative interaction. This is why comblike polymers have come to be accepted as convenient matrices for constructing LC polymers. Already a few hundred liquid-crystalline polymers with various mesogenic side groups have been synthesized. 

Table 1. Some types of liquid-crystalline polymers with mesogenic side groups...

Worthy of attention are the attempts to produce LC polymers on the basis of inorganic polymers those are polyphosphazenes with mesogenic side groups (cholesterol) although the first results to have been published were not promising40. A broad class of heterocyclic compounds could have probably contributed to the synthesis of new systems. The synthetic possibilities of this approach are quite evidently far from being exhausted. 

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