STRUCTURE OF MANY-ARM STAR POLYMERS IN SOLVENTS OF VARYING QUALITY - A MOLECULAR-DYNAMICS STUDY

A molecular simulation of many-arm star polymers in solvents of varying quality is presented. The number of arms f in each star covered the range 3 less-than-or-equal-to f less-than-or-equal-to 80 with N = 50 and 100 monomers per arm. The resulting equilibrium structures are compared to scaling predictions based on the blob model and to experimental results. The monomer density rho(r) from the center was found to fall off as a power law, r(-a), for both a good and THETA solvent in agreement with the scaling predictions. The free ends were found to be excluded from a region near the center of the star and the distribution of center-to-end distances R was found to be well approximated by a Gaussian for many-arm stars (f greater than or similar to 20) for all solvents. For small f, there were some deviations from a Gaussian form, particularly for small R. For both a good and THETA solvent, the relaxation time for the shape fluctuations depended imperceptibly on the number of arms f.