A new theory for rotational isomeric states: polysilanes lead the way

Conformational studies of polysilanes have led to a new model for rotational isomerism. The new model applies to most linear polymers and oligomers other than hydrocarbons, for which the familiar anti and gauche minima are valid. According to the model, the permitted rotational minima, their symbols and their approximate intrachain torsional angles ω are: transoid, T, ±165°; deviant, D, ±150°; ortho, O, ±90°; gauche, G, ±55°; and cisoid, C, ±40°.