Linear rheology of multiarm star polymers diluted with short linear chainsa)

We present experimental results on the linear rheology of multiarm star/linear polymer mixtures, the latter having molecular weight much smaller than the star arm molecular weight. In such a case the linear chains act as ideal macromolecular solvents, which dilute entanglements of the arms. Using different star polymers we show that it is possible to account for this dilution and describe the linear rheology of the mixtures using the Milner–McLeish theory for arm relaxation, complemented by the longitudinal modes of stress relaxation and high frequency Rouse modes. A universal description of the isofrictional arm relaxation time as a function of the number of entanglements is obtained for stars of any functionality and degree of dilution. The slow structural mode, related to the diluted star’s colloidal core, also depends on the number of entanglements, but in a more complex way. © 2003 The Society of Rheology. @DOI: 10.1122/1.1529172#