Composites of natural fibers and thermoplastics can be combined to form new enhanced materials. One of the problems involved in this type of composites is the formation of chemical bonds between the fibers and the polymers at the interface. This work presents a study where low energy glow discharge plasmas are used to functionalize cellulose fibers implanting polystyrene between the fibers and the matrix that improve the adhesion of both components. The interface of polystyrene was synthesized by continuous and periodic glow discharges on the surface of the cellulose fibers. The results show that the adhesion in the fiber-matrix interface increases with time in the first 4 min of treatment. However, at longer plasma exposures, the fiber may be degraded reducing the adhesion with the matrix. (c) 2006 Wiley Periodicals, Inc.