A. Kadimi,a,b, H. Kaddamia,, M. Raihanea, Z. Ounaiesb , aLaboratory of Organometallic and Macromoleculaire Chemistry- Composite Materials, Faculty of Sciences and Technologies, Cadi ayyad University, Avenue AbdelkrimElkhattabi, Marrakech, Morocco bPennsylvania state University- Department of Mechanical and Nuclear Engineering 157B Hammond Builiding . Universiy, Park, PA 16802-1412, U.S.A Abstract: The concept of reinforced polymer materials with nanocellulose (CNC: cellulose nanocristals or NFC: nanofibrils of cellulose) has known rapid advances and considerable interest owing to their renewable character, high mechanical properties low density, availability and diversity of the sources. Numerous research studies have shown that the addition of nanocellulose to a polymer matrix leads to an enhancement in mechanical and dielectric properties. The association of nanocellulose and a polymeric matrix enabled production of new nanocomposites with original properties. Few papers have been published on the dielectric properties of NFC-based nanocomposites. Recently, Ladhar et al1-4 have studied the dielectric relaxation of nanocomposites based on nanocellulose-filled rubber and showed how the nanocellulose characteristics influence electrical propertie of their nanocomposites. This paper aims to study dielectric properties of new nanocomposites based on cellulose nanofibrils (NFCs) extracted from the rachis of date palm three by TEMPO mediated oxidation and copolymers of controlled properties containing fluorinated and nitrile derivatives. In the first step copolymers of acrylonitrile (AN) and 2, 2, 2-Trifluoroethyl methacrylate (MATRIF) with different proportions were synthesized by emulsion polymerization, the corresponding synthesis yield is between 58% et 60%. The homopolymer poly (MATRIF) and poly (AN) were also prepared to be used as reference materials, the synthesis yieldsare 60% and 68%, respectively.These copolymers exhibit glass transition temperatures (Tg)