Synthesis and Linear Viscoelasticity of Polystyrene Stars with a Polyketone Core

We report on a novel synthetic route to synthesize relatively large quantities of polystyrene (PS) star polymers with targeted arm functionality and molar mass and their theological properties in the molten state. The synthetic route involves grafting styrene monomers onto a modified (aliphatic, alternating) polyketone backbone with a specific number of initiating grafting sites using controlled atom transfer radical polymerization (ATRP). Several polyketone precursors were used. This resulted in a large array of star polystyrenes with nonspherical cores and varying average arm length and number of arms. Their linear viscoelasticity was investigated and discussed in the context of the known response of anionically synthesized stars. Using a powerful characterization toolbox, including state-of-the-art interaction chromatography, rheometry, and tube modeling via the branch-on-branch (BoB) algorithm, we have assessed the viscoelasticity of these star polymers quantitatively. In particular, we have demonstrated a variability in molecular structure, which differs substantially from their anionically synthesized counterparts. Hence, whereas this new family of star polymers is not recommended for fundamental studies of polymer physics such as the molecular origin of relaxation mechanisms without prior extensive fractionation, they could be used in studies of mixtures as well as industrially relevant processing operations that require large amounts of polymeric stars.