Dimensional and hydrodynamic factors for flexible star polymers in the good solvent limit

Star chains composed of arms with uniform length were generated on a simple cubic lattice by the Monte Carlo method using the enrichment algorithm, which enabled us to obtain chains with total segment numbers (N) up to 1200. The number of arms (f) ranged from 2 to 24. The radius of gyration ((S²)^1/2), the dimensionless intrinsic viscosity (E), and the hydrodynamic radius (R_H) were evaluated as functions of f and N by averaging over more than 4000 samples. The calculations of E and R_H were made according to Zimm's method. It was found that the radius expansion factor (α_S) for star chains with long arms obeys the relation α_s² = 1.53z^2/5, which is known for long flexible linear chains, where z is the excluded volume parameter. The ratios of (S²), E, and R_H of star chains to those for linear chains were evaluated as functions of f. These ratios obtained and the Flory factors for the intrinsic viscosity and RH extrapolated to N^-1/2 → 0 reproduced experimental data well.