KINETICS OF HOMOPOLYMER COLLAPSE

Langevin-equation simulation is used to study the dynamics of a simple model of homopolymer collapse at infinite dilution for polymers of lengths N= 100, 200, 300, 500, and 1024 units. Lennard-Jones potentials are chosen to represent the bead-bead interactions and a harmonic potential bonds nearest-neighbor beads. The Flory coil-to-collapsed globule transition is brought about by an adjustment of the Lennard-Jones potential interactions. The average cluster size and distribution, along with the radius of gyration are used to characterize the collapse dynamics. Our results indicate that there are several kinetic mechanisms that lead to a collapsed polymer. At early times the dominant mechanisms involve cluster creation and growth by adsorption of slack polymer, whereas for later times the mechanism involves cluster coarsening. For this latter mechanism we find that the average cluster size 〈s〉 grows as 〈s〉 =Atz, where z is dependent on u3, the third virial coefficient. Depending on the value of u3 we determine two values for z, first, z=0.60±0.02 for u3 not equal to zero and second z=0.66±0.03 for u3 equal to zero, both representing a departure from Lifshitz-Slyozov theory. © 1995 American Institute of Physics.