The dynamic effects of unentangled star-shaped polymers with extremely small branches on the plasticization of miscible polymer blends are investigated using ultra-small branched star poly(epsilon-caprolactone)s (USB-SPCLs), poly(vinyl chloride) (PVC), and their blends. Photon correlation dynamics of USB-SPCLs supports our previous suggestion that a whole USB-SPCL molecule acts as a single coarse-grain unit with dynamically-equivalent branches because of the extremely small branches, resulting in the total-molecular-weight-dependent Rouse dynamic behaviors of USB-SPCLs, regardless of the molecular architectures. The dynamic light scattering intensity autocorrelation curves of miscible PVC/USB-SPCL blends reveal that strong intermolecular interactions between PVC and USB-SPCL molecules determine the dynamic homogeneous behaviors of the blends despite their significantly different mobilities. The molecular motions of the blends depend on the total-molecular-weight-dependent Rouse dynamic behaviors of USB-SPCLs. These dynamic results clearly show the plasticization of the entangled neat linear PVC matrix by distinctive and rapid molecular mobility of USB-SPCLs. (C) 2016 Elsevier Ltd. All rights reserved.