Diffusion-controlled intrachain reactions in polymer: An analytical   model
  A theory of diffusion-controlled intramolecular reactions of polymer chain in dilute solution is formulated. Our model is based on the widely used diffusion-reaction formalism of Wilemski and Fixman (J. Chem. Phys. 60, 866 (1974). Our model is more general than the model proposed by Wilemski and Fixman, in the sense that our model considers the motion of both close and open chain polymer explicitely. It is quite unlikely that the motion of close chain polymer do not play any role in the loop formation dynamics, but unfortunately this fact was not considered in any of the earlier studies. 
Aniruddha Chakraborty
cond-mat.soft