Viscoelasticity near the gel point: A molecular dynamics study - art. no. 031505

We report on extensive molecular dynamics simulations on systems of soft sp heres of functionality f. i.e., particles that are capable of bonding irrev ersibly with a maximum of f other particles. These bonds are randomly distr ibuted throughout the system and imposed with probability p. At a critical concentration of bonds. p(c) approximate to 0.2488 for f = 6, a gel is form ed and the shear viscosity eta diverges according to eta similar to (p(c)-p )(-s). We find s approximate to 0.7 in agreement with some experiments and with a recent theoretical prediction based on Rouse dynamics of phantom cha ins. The diffusion constant decreases as the gel point is approached but do es not display a well-defined power law.