Modificação de nanofibrilas de celulose com polianilina para utilização em eletrônicos flexíveis visando à melhoria de suas propriedades elétricas

Abstract

In recent decades, biodegradable products have been extensively considered in electronics. Cellulose is an insulating biodegradable polymer with high potential due to its dielectric character. Doped polyaniline (PANI) is a highly studied material that has resistive and capacitive properties. The present work proposes the fabrication of dielectric films with cellulose nanofibrils modified with PANI through in situ polymerization. As cellulose source, it was used commercial pulp fiber with 0.81 ± 0.01 mm length and 15.9 ± 0.3 μm diameter. The fiber chemical content was 86.3 % cellulose, 12.9 % hemicelluloses and 0.8 % extractives and ashes. Cellulose nanofibrils were obtained by mechanical shear with 1500 rpm and amperage between 4 and 6 A. Citric acid and chloric acid with concentration 0.1 M, 0.5 M, 1.0 M and 2.0 M were used in the polymerization process. The solution was filtered then dried with pressured plates at 50°C for 24 hours. The films had homogenous morphology without cellulose and PANI with no phase separation. The films with higher acid concentration had a superior hydrophilic character then others, showed by high frequencies bands in FTIR spectra. There were no significant color differences between cellulose and PANI films. Films with PANI doped with HCl 1.0 M and 2.0 M had higher capacitance values and dielectric constant due to a better doping of PANI, higher film density and higher water content in films in environmental conditions. The electrochemical impedance spectroscopy (EIS) were not conclusive due to a poor film deposition on substrate. The equivalent circuits provided by EIS had shown a decreasing in substrate (Rs) and charge transfer resistance (Rct) which contributed to the films capacitive behavior. Therefore, films with PANI doped with HCl in higher concentrations were the best suited for electronics regarding its higher dielectric constant and humidity response.