Poly((E)-epsilon caprolactone)-grafted cellulose nanowhiskers (extracted from ramie: CNWr) synthesized by ring-opening polymerization of the corresponding lactone [1] were studied as "masterbatches" by melt-blending within its commercial poly(epsilon-caprolactone) matrix (PCL). For sake of comparison, unmodified CNWr were also dispersed in PCL The goal of this study consists to evidence the impact of the covalent grafting of CNWr surface on thermo-mechanical properties of the commercial matrices. Atomic force microscopy (AFM) attests of the excellent dispersion of the cellulose nanowhiskers within PCL matrix. As a result of the excellent interfacial compatibility between the nanofiller and the matrix, the thermo-mechanical and theological performances were largely enhanced. (C) 2011 Elsevier Ltd. All rights reserved.