Combinatorial rheology of branched polymer melts

An algorithm is presented for predicting the linear viscoelasticity of polydisperse polymers Containing long side branches with arbitrary distributions of branch length and branch location along a backbone. The algorithm gives semiquantitative predictions of literature data for a wide range of polybutadiene melts, including monodisperse linear, star, mixed linear and star, pom-pom, and comb polymers. Huge differences (several orders of magnitude) are predicted in zero-shear viscosities for samples that have the same weight-average molecular weight (200 000) and the same branching fraction but have different branching structures. It is shown that information on branching structure can be inferred by combinatorially measuring theological properties on series of blends of the branched polymer with a linear, or well-defined branched, polymer.