Rheology of polybenzyl ether dendrimers their copolymer and blends

The dynamic rheological behavior of pure polybenzyl ether dendrimers and their copolymers have been studied in the molten state. The pure polybenzyl ether dendrimer generation 4 and generation 5 show Newtonian behavior whilst the generation 3 appears to be a very slightly shear-thinning within the deformation rates investigated, the behavior also being a function of thermal pretreatment. When the dendrimer component was included as a dendritic polystyrene copolymer (covalently attached), the viscosity was much lower compared to corresponding polystyrene of similar molecular weight. The same concentration of dendrimer could be physically blended into the polystyrene forming an immiscible mixture, which also reduced viscosity. However, if the dendritic component was covalently attached, it had a lower viscosity than if physically blended at the same concentration.