Melt rheology of star polymers with large number of small arms, prepared by crosslinking poly(n-butyl acrylate) macromonomers via ATRP

We investigate the linear viscoelastic response of model poly(n-butyl acrylate) star polymers with moderate to high functionalities and unentangled arms. We discuss the data by comparing against linear polymers of the same chemistry and molar masses ranging from unentangled to well-entangled. Further, we provide a quantitative assessment of the stars rheology by using a simple model accounting for both the high-frequency response (influenced by segmental dynamics) and the low-frequency arm relaxation. Deviations are observed and expected for the high-functionality case. This work confirms the universal mechanism of arm relaxation governing the star rheology, and further points to a number of subtle issues that need to be dealt with in order to obtain accurate quantitative description of the dynamics.