LOCAL CONFORMATION OF REGULAR STAR POLYMERS IN A GOOD SOLVENT - A MONTE-CARLO STUDY

Off-lattice Monte Carlo simulations were performed on linear and la-ar m regular star polymers with up to 472 repeat units in the excluded-vo lume regime. For both topologies, the overall size scales asymptotical ly with molecular weight through a Flory exponent, v = 0.588, but for finite molecular weights, the apparent exponent is slightly different in the case of the radius of gyration and of the root-mean-square end- to-end distance and definitely smaller in the case of the hydrodynamic radius. The interatomic distances within the star follow a a-fold beh avior, according to whether the two atoms belong to the same arm or to different arms. This result is related with the peculiar behavior of the scaler products among the bond vectors. If these belong to the sam e arm and are remote from the branch point, the scalar products follow the same pattern as in the linear chain. If however the bonds are clo se to the branch point, the scalar products are much larger and essent ially constant, indicating a substantial arm stretching. Conversely, i f the two bonds are on different, arms, the scalar products across the branch point drop at once by more than 1 order of magnitude. Therefor e, the initial arm directions are essentially noncorrelated, and the i nterarm repulsions are best accommodated with a minimum entropy loss.