Rod-Shaped Chemical Structures

Because the amide groups are located in the trans positions on the phenylene rings, there is minimal bond rotation out of the chain axis. 

Another example is a copolymer of p-hydroxybenzoic acid,p,p -biphenol, and terephthalic acid, creating the polyester structure 

the ester groups, together with the para-bonded phenylene rings, form strictly rodlike structures. 

Another type of liquid crystalline polymers are those having rod-shaped side chains. TTius, the backbone may be a random coil, but the side chains are organized into one- or two-dimensional liquid crystals. The stiff backbone types make very high modulus fibers and high temperature plastics. The side chain types are useful for their action in magnetic and electrical fields. (Note the behavior of battery-driven liquid crystalline watches, for example. The liquid crystalline material is held between crossed Nicols the orientation of the molecules is controlled by an electric field.) In the following, the terms mesophase and liquid crystal phase are used interchangably. 

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