(621b) Anomalous Crystallization Behavior of Ring Polymers

We have modeled the crystallization of cyclic polyethylenes using coarse-grained Langevin dynamics simulations and compared with the behavior of linear polyethylenes. We have studied various features of polymer crystallization including early stage nucleation kinetics, lamellar thickness, growth kinetics, and melting. Contrary to expectations from equilibrium thermodynamics, ring polymers melt at lower temperatures than the corresponding linear polymers. The rings crystallize faster and exhibit several metastable lamellar thicknesses. The topological effect arising from the absence of chain ends is found to be significant even at large molecular weights. Comparison of our simulation results with available experimental data help to resolve several long-standing puzzles in the determination of equilibrium melting points and crystallization kinetics.