General Empirical Description of Network Segments

2 Deformation of Aromatic Segments with Bridges Consisting Exclusively of Coaxial Single Bonds 

These polymers are as close as possible to being truly rodlike. If, however, the N-H in the polybenzimidazole or -O- in the polybenzoxazole are replaced by -S- to give the polybenzothiazole analogue, then the single bonds along the chain cease being fully coaxial and the polybenzothiazole chain adopts an 

3 Deformation of Stiff Aromatic Segments with Bridges Consisting of a Single Non-Coaxial Bond Connecting Two Coaxial Bonds Between Aromatic Groups 

Because neither angle a nor p equals 120° and a — p 0, there is a curvature imparted to the overall chain direction, a curvature reflected in the magnitude of the persistence length, a. The magnitude of a is, hence, inversely proportional to a — PI [663]. It is well accepted that in p-BA p-PT and p-BT the amide group exists in the planar trans conformation. Relative to the aromahc ring, the amide 

In a similar fashion, we represent the syn-conformers as ( + )syn- and ( — )syn-, with torsional angles between the carbonyl and N-H groups of 0° and 60°, respectively  

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