1.1 Static Flexibility

The static flexibility of the chain in equilibrium is determined by the difference between the levels of the energy minima corresponding the gauche and trans states, Δε.

If Δε < kT, the g₊, g_- and t states occur with similar probability, and so the chain can change direction and appears as a random coil.

If Δε takes on a larger value, then the t conformations will be enriched, so the chain will be rigid locally, but on larger length scales, the eventual occurrence of g₊ and g_- conformations imparts a random conformation.

Overall, if we ignore details on some length scale smaller than l_p, the persistence length, the polymer appears as a continuous flexible chain where

(1)

where l₀ is something like a monomer length.