Diatomic Molecules and Polymer Chains

Considering a free diatomic molecule, thermal fluctuations result in either extension or compression of the bond, depending on the packing density and geometric confinement. Weiner et al. have shown that the time-average bond force has two 

If the diatomic molecules are connected to each other to form a polymer chain, we should distinguish between an external force (if any) applied to chain ends and a force at a particular bond within the chain. Because the total strain is distributed over multiple covalent bonds and torsional angles, tension in an individual bond is usually different from the externally applied force [63, 64]. Even for unperturbed polymer coils at zero external force, the average bond force is non-zero [63]. For a single chain at a zero displacement of the end-to-end vector, the bond tension was found as = 2kT/rp and viewed as the centrifugal force acting in a bond 

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