Collapse transition of a stiff chain

We have derived the mean square end-to-end distance of a semiflexible chain with the two-body interactions using perturbation theory. Following the usual arguments, we have generalized the fifth-power type relation for the chain extension factor to arbitrary chain stiffness and the three-body interactions. Similar to the flexible chain, a stiff chain of finite length undergoes the coil–globule transition if the two (three)-body interaction is above (below) a certain critical value. The stiffness dependence of the critical values of the two-body and three-body interaction parameters is calculated.