Rheology on the Dispersion of Acetylated Cellulosese Nanocrystals in Polylactic Acid (PLA) Nanocrystalline cellulose (NCC), a new family of natural, cellulose-based materials with fibre diameters of 20-50 nanometers long, is a powerful reinforcing agent. It is primarily used in biopolymers like polylactic acid (PLA), to produce composites of desired mechanical and physical properties. The key challenge in the development of such composites lies in uniformly dispersing cellulose into the PLA matrix. Cellulose, owing to its hydrophilic nature, tends to agglomerate, resulting in crack or failure of such composites. A possible strategy to minimize this effect is surface acetylation which is a chemical modification of NCC surface. In this study, a series of nanocomposites using surface acetylated NCCs with acetic anhydride are prepared by solvent casting technique. Rheological measurements are used to study and quantify the state of dispersion. Low frequency linear viscoelastic behaviour is analysed using scaling concepts for fractal networks to determine the degree of network formation. Moreover, the high frequency behaviour of the moduli is used to assess the dispersion quality. Overall dispersion is affected by the flow induced orientation as well as the formation of aggregate networks of NCCs. The results from the analysis of the linear viscoelastic data are then compared to structural features extracted from electron microscopy. Keywords: Nanocrystalline Cellulose, Rheology, Polylactic Acid (PLA), Dispersion