Combined Synthesis, TGIC Characterization, and Rheological Measurement and Prediction of Symmetric H Polybutadienes and Their Blends with Linear and Star-Shaped Polybutadienes

We report the synthesis and characterization by temperature gradient interaction chromatography (TGIC) and rheometry of a symmetric H-shaped polybutadiene (PBd) that we call "HA20B40", and of a symmetric star-shaped synthetic precursor of HA20B40, and the use of these characterization data to test and validate advanced tube models (the hierarchical and, to a lesser extent, the BOB models) for long-chain branched polymers. Furthermore, by deliberately adding additional well-characterized linear and star-branched polymers into HA20B40, we mimic the effect of impurities in the sample to test the ability of the hierarchical model to account for the effect of similar such impurities, which are detected by TGIC. Our modeling predictions for HA20B40 and its blends with star and linear polymers show very good agreement with measured rheological data, indicating that the modeling validation is successful for the symmetric H-shaped polymers. We then test the hierarchical model further using literature data for symmetric H-PBds, for which the TGIC and experimental rheology data were published. We find that as long as the polymer composition is accurately determined, the hierarchical model can calculate the rheological behavior accurately. The theory can therefore be used to help to identify the composition or impurities, which are almost always present at low levels at least in such topologically complex samples.