Brownian dynamics study of the shape of star and linear polymers in different regimes

Brownian dynamics computer simulations are used to investigate the shape of linear and star polymers in three regimes: (1) excluded volume, (2) θ, (3) collapsed. It is found that the mean-square radius of gyration 〈S2〉 displays a different power law exponent in the different regimes: 〈S2〉∼(1) (N−1)1.2 (2) (N−1)1.0, and (3) (N−1)2/3 where N is the number of chain units. The pair-correlation function using the central vertex bead as the origin reveals the polymer structure. In the collapsed regime the structure resembles face-centered-cubic (FCC) packing. The g ratio of star/linear chains as well as the asphericity of the polymers have been determined for the three regimes.