Rigid-chain polymers mesogenic groups

Hence, although the equilibrium rigidity of the main chain of polymer molecules with mesogenic side groups is not h h (A 50 A), their polar groups are oriented in the electric field by large-scale intramolecular motions characteristic of rigid-chain polymers. 

Structure of which is identical to their corresponding low molecular weight disk-like counterparts. Rigid chain polymers, such as nucleic acids and polypeptides [5b, 66], are also well known to produce lyotropic columnar mesophases with appropriate solvents. The poly(di-n-alkylsilanes) and poly(di-n-alkylsiloxanes). Fig. 12, with only alkyl side groups and deprived of any mesogen [67] are examples of polymers showing thermotropic columnar mesophases which need to be analyzed in more detail. 

Liquid crystalline thermosets (LCT) with a rigid rod-like mesogenic group capped firom both ends by reactive fimctional groups can be used as matrices for production of advanced composites, coatings or adhesives (1, 2). hi this case ordering of the chains of the final network polymer is the only way to improve its physical and mechanical properties. 

Horie and his co-workers [131-135] have made extensive use of fluorescence spectroscopy to probe the microstructures of MCLC polymers. The first such polymer to be studied [131,135] was the all aromatic, rigid rod polyester, 65, with long, flexible side-chains attached to a pyromellitic ester mesogenic group. 

The term mesogenic group , for the purposes of this review, refers to the part of the polymer chain that is composed of the rigid, linear segments and the atoms or functional groups which link them together in a linear array. It is this part of the polymer chain that ultimately determines whether or not the polymer will be liquid crystalline, within what range the transition temperatures will occur for a thermotropic polymer, and what type of mesophase can be formed. 

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