Problems of Internal Friction

Section VI. 1.2 introduced the effects of internal barriers on the friction coefficient of one dumbbell. For a given elongation r (assumed small) and elongation rate dr/dt = V, the friction forces (f) contain three separate contributions, to be presented below. 

In the Rouse picture [eq. (VI. 12)] this was additive and thus linear in N 

With the more realistic Kirkwood picture, we would have [in analogy with eq. (VI.33)]  

Energy barriers between different chain conformations (such as trans and gauche for simple carbon backbones) are responsible for a form of friction discussed by Kuhn. The result is given in eq. (VI. IS). 

The two processes above do not account entirely for the data. Very early, a third friction term was proposed by Cerf with the structure 

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