The novelty lies on the molecular level investigation of the end group functionality on rheological properties of fractionated, monodisperse oligomeric perfluoropolyethers (PFPEs) with various molecular weights and chain-end functionalities in this study. A sharp transition observed in the slope of the shear viscosity at a critical molecular weight for PFPEs was interpreted based on temporal tube mechanism caused by end group agglomeration of strong functional polar end groups. The temperature dependence of the shear viscosity was found to yield an Arrhenius form, determining the flow activation energy and hydrodynamic volume. The flow activation energy was also compared to the activation energy for surface diffusion to examine the role of end group-solid surface interaction. Modified Cole-Cole plots for storage and loss moduli along with polymer relaxation show the microstructural changes due to the interaction of PFPE end-group, which alters effective molecular weights. (C) 2010 Elsevier Ltd. All rights reserved.