DYNAMICS OF THE SWELLING OR COLLAPSE OF A HOMOPOLYMER

We study the dynamics of a polymer when it is quenched from a theta to a good or bad solvent, by means of a Langevin equation. The variation of the radius of gyration is studied as a function of time. For the f irst stage of collapse or swelling, the characteristic time scale is f ound to be proportional to N-4/3. Other scaling laws are derived for t he diffusion regime at larger times. Although the present model is sol ved only for homopolymers and does not include hydrodynamic interactio ns, these results may be a first step towards the understanding of the early stages of protein folding.