Modificação de filmes do compósito alginato de sódio-poli(etileno glicol)- glicerol com óxidos de tungstênio e titânio: interações físicas que influenciam no transporte de carga

Abstract

The association between polymers and ionic salts by physical interaction, is an efficient way of making films with interesting mechanical and electrical properties. Although physical combination of polymers and salts and the obtaining of self-sustaining film by evaporation method can be easily achieved, the properties of this new compound may be different from the separate components. This work describes the electrical properties of new composite sodium alginate/poly(ethylene glycol)/glycerol with and without modification with the salts of sodium tungstate and titanium tetrabutoxide through physical interactions among them. The preparation of the film made by the sol-gel method, both the pure polymer matrix (sodium alginate/poly (ethylene glycol)/glycerol) and the polymeric matrix doped with varying rates 1, 2, 3 and 4 mL solution of sodium tungstate at a concentration of 1 mmol/L, and 0,1, 0,2, 0,3, and 0,4 ml of titanium tetrabutoxide in a sample of the polymer mixture, was studied the mixture of higher concentrations of the two salts associated. The films were characterized by attenuated total reflection (ATR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-Ray Spectroscopy Energy Dispersive (EDS) and the contributions of salts on the electrical properties of the films were analyzed by electrochemical impedance spectroscopy (EIS). The film of sodium alginate with poly (ethylene glycol) has mechanical rigidity making it difficult the workability of the film, however, the addition of glycerol reduces the intermolecular forces between the polymer chains reducing such fragility due to the small size of the chain, allowing it to be inserted more easily in the polymer chain, and thus exert greater influence on the mechanical properties of the poly(ethylene glycol) larger molecule. Physical interactions are proven through the ATR spectra. The characteristics bands of alginate are not displaced, increasing the area of the bands and favors of vibrations in the presence of glycerol occurs. The XRD patterns showed the predominance of the behavior amorphous in films. SEM analyzes showed the predominance of a smoother surface when glycerol is present in the film, and when the salts are associated micrographs show the existence of pores and surface irregularities, as well as heterogeneity. When salts are associated in the same film there is a predominant distribution of microstructures. Through the EIS it was observed that the association of glycerol and PEG in NaAlg film produces a characteristic behavior of charge transport with a conductivity on the order of 10-4 Ω-1 .cm -1. When the composite is associated with sodium tungstate presents a charge storage behavior, and when the association is with the titanium tetrabutoxide charge transport is favored, and in the film with the mixture of the salts the conductivity value is in the order 10-3 Ω -1 .cm -1. The association of salts increases the extrinsic ionic mobility of the composite and improvement in their conductive properties.