Interfacial flow behavior of highly entangled polybutadiene solutions

Strong flow behavior of entangled polymer solutions is investigated to illu strate a correlation between linear viscoelastic properties and interfacial slip flow behavior. It is found that entangled polybutadiene (PBD) solutio ns (made of 1,4-PBD and oligomeric ED of varying vinyl contents) exhibit an interfacial stick-slip transition at a critical stress about one-third of their plateau modulus. The magnitude of the transition, as quantified by th e extrapolation length b, depends strongly on the level of chain entangleme nt which is determined by the concentration phi and reflected in the magnit ude of the solution viscosity eta. Analogous to the case of polymer melts, the experimental data reveal the same molecular weight dependence for b as that for eta measured at a constant stress. The phi dependence of b is univ ersal in the sense that its scaling behavior b proportional to phi(3) holds independently of temperature and the vinyl content of oligomeric ED solven t. The phi dependence of eta is however more complicated because it depends on the segmental friction coefficient zeta(phi,T) besides the tube diamete r a(phi).