Linear Melt Rheology of Pom-Pom Polystyrenes with Unentangled Branches

We measured the linear viscoelastic properties of a series of polystyrene melts with pom-pom architecture consisting of backbones ranging from marginally to well-entangled (of molecular weight M b ), end-grafted with q unentangled branches ( M br ) per backbone end. In this case, the branches relax very fast and act primarily as solvents for the backbone. Using a time-marching tube-based model, we showed that, in such a case only, the pom-pom polymer is equivalent to a blend of long ( M L ≈ M b + 2 M br ) and short ( M S ≈ M br ) linear chains with respective proportion ( M b + 2 M br )/2( q − 1) M br .