Dielectric behaviour of plasma hydrogenated TiO 2 /cyanoethylated cellulose nanocomposites.

The interface between the polymer and nanoparticle has a vital role in determining the overall dielectric properties of a dielectric polymer nanocomposite. In this study, a novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO 2 nanoparticles surface modified by hydrogen plasma treatments was successfully prepared with different weight percentages (10%, 20% and 30%) of hydrogenated TiO 2 . Internal structure of H plasma treated TiO 2 nanoparticles (H-TiO 2 ) and the intermolecular interactions and morphology within the polymer nanocomposites were analysed. H-TiO 2 /CRS thin films on SiO 2 /Si wafers were used to form metal-insulator-metal (MIM) type capacitors. Capacitances and loss factors in the frequency range of 1 kHz to 1 MHz were measured. At 1 kHz H-TiO 2 /CRS nanocomposites exhibited ultra-high dielectric constants of 80, 118 and 131 for nanocomposites with 10%, 20% and 30% weight of hydrogenated TiO 2 respectively, significantly higher than values of pure CRS (21) and TiO 2 (41). Furthermore, all three H-TiO 2 /CRS nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10 -6 A cm -2 -10 -7 A cm -2 ). Leakage was studied using conductive atomic force microscopy (C-AFM) and it was observed that the leakage is associated with H-TiO 2 nanoparticles embedded in the CRS polymer matrix. Although, modified interface slightly reduces energy densities compared to pristine TiO 2 /CRS system, the capacitance values for H-TiO 2 /CRS-in the voltage range of -2 V to 2 V are very stable. Whilst H-TiO 2 /CRS possesses ultra-high dielectric constants (>100), this study reveals that the polymer nanoparticle interface has a potential influence on dielectric behaviour of the composite.