Correspondence relation with respect to entanglement among different simulation models: comparison between bead-spring and bond fluctuation model

摘要

A novel index for comparing different simulation model polymers with respect to entanglement is proposed. It is the number of elements N_e~* of ring polymers whose average number of entanglement per molecule is unity; N_e~* can be calculated with a small-scale computer simulation. We also proposed a method to equilibrate the entangled ring polymers. As an example we calculated N_e~* with a molecular dynamics simulation using a bead-spring (BS) model which is equivalent to the model proposed by Kremer and Grest [J Chem Phys 92 (1990) 5057], and with a Monte Carlo simulation using bond fluctuation (BF) model. We obtained N_e~* = 82 ± 1 for BS model with volume fraction φ = 0.43 and N_e~* = 59 ± 1 for BF model with φ = 0.5. By comparing with the recent result of our group, N_e = 89 for BF model with φ = 0.5, we can assume that N_e approx= 1.5 N_e~*. If this assumption holds for BS model, its N_e is estimated to be 120, which is 3.4 times greater than the estimated value by Kremer and Grest. The origin of this difference is discussed.