STAR POLYMERS VIEWED AS ULTRASOFT COLLOIDAL PARTICLES

Combining statistical-mechanical theories and neutron-scattering techn iques, we show that the effective pair potential between star polymers is exponentially decaying for large distances and crosses over, at a density-dependent corona diameter, to an ultrasoft logarithmic repulsi on for small distances. We also make the theoretical prediction that i n concentrated star polymer solutions, this ultrasoft interaction indu ces an anomalous fluid structure factor which exhibits an unusually pr onounced second peak.