Polymer chains repetition symmetry groups

Figure 2.15 line repetition symmetry groups and corresponding sequences of torsion angles for cis and trails polydienes. Position of mirror planes (m), inversion centers (i), and binary axes (2) along polymer chain are also indicated. Torsion angle of single bond, CHA-CHA, is assumed to be trails (T) in both cis and lruns polydienes. 

When A A or B B, the symmetry is lower and the only possible line repetition groups are s(M/N) and tc for isotactic and syndiotactic polymers, respectively, in both cis and trans configurations. In these cases, two independent torsion angles in the main chain define the regular conformation (Oi and 02 in Figure 2.15). 

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