Effect of chain length on structure and dynamics in a melt of semiflexible rings

We investigate structure and dynamics of semiflexible rings in a melt by molecular dynamics simulation. Our research mainly focuses on chain length effect. We observe a power law of the intrachain structure factor of rings at intermediate length scale. The fractal dimensions of 1 and 3 at different length scales are reported. By analytical expression for the intrachain structure factor, the value of fractal dimensions is considered to be related to the features of rod and ring, respectively. With the increase of the chain length, the width of the Gaussian distribution of bond angles and the mean value of bond angles show significant increases. Further, we find that chain length induces ultra-soft sphere-like behavior in radial distribution function and short-range attractive effective potential. By combining this with the separation between self- and collective intermediate scattering function, we propose that the presence of the short-range attractive effective potential is the structural signal of the emergence of interpenetration and cluster in ring polymers. Finally, a significant increase of the decay exponent of diffusion with chain length in the melt of semiflexible rings is found. Interpenetration of semiflexible rings is supposed to be responsible for the large value of exponent