Internal coordinates of a polymer chain and its hindered rotation

1 Internal coordinates of a polymer chain and its hindered rotation 

The energy difference Ae between the t position and the g, g positions decides the average population of the carbon atoms in thermal equilibrium state. It is related to the flexibility of the chain. For instance, the average length X of the continuous trans sequence ttttt... is given by 

Polymers with simple chemical structure take values of order Ae 1 kcal mol AE 4-5 kcal mol but the barrier height AE can be higher if the side groups are replaced with larger ones, and also if there is strong interaction, such as dipole interaction, hydrogen bonds, etc., between them. 

---