COMPUTER-SIMULATION STUDY OF THE STRUCTURE AND DYNAMICS OF RING POLYMERS

We study the equilibrium structure and dynamics of unconcatenated, unk notted polymer rings in the melt. In agreement with earlier studies we find that rings in the melt are more compact than linear chains. In a ddition, we show that the ''correlation hole'' in the equilibrium corr elation functions is deeper and wider for rings than for linear chains . This suggests that there is less interpenetration in the melt of rin gs compared to the melt of linear chains. We also find that rings diff use faster than linear chains. For smaller rings this result agrees wi th the earlier work of Muller, Wittmer, and Gales [Phys. Rev. E 53, 50 63 (1996)]. The main result of this study is that faster ring diffusio n persists up to ring size at least ten times greater than the entangl ement crossover of Linear chains. Furthermore, we show that. for all r ing sizes studied, the dependence of the single-chain relaxation time on ring size is weaker than for linear chains. Finally, we find that b oth faster diffusion and faster relaxation can be rationalized by the smaller size of rings: The dependence of self-diffusion coefficient an d relaxation time on radius of gyration of rings and linear chains is remarkably similar. (C) 1998 American Institute of Physics.