Molecular recognition of biomolecules by synthetic receptors requires modular assembly of various components to complement the molecular characteristics (sizes, topologies, and functional groups) of the substrate. A number of receptors for biorelevant molecules containing oxoanions have been assembled from a bicyclic chiral guanidine subunit. Several receptors accelerate or catalyze reactions proceeding through anionic transition states. Among the structures recently prepared, a receptor incorporating a calix[6]arene subunit has been developed, showing high affhity for phosphocholine derivatives. Chains of tetraguanidinium sulfates form double helices in solution. These substances strongly induce formation of a-helical conformations in Asp rich peptides.
Corrosion is one of the great problems that many industries face and that generates losses of millions of dollars worldwide. The aim of this work was to evaluate the capacity of polyaniline to increase the anticorrosive capacity of a commercial epoxy paint. Polyaniline was chemically synthesized by oxidation with ammonium persulfate and doped with oleic acid. Polyaniline was added to the paint in various concentrations to evaluate its behavior as an additive to improve the anticorrosion capacity on stainless steel samples. An electrochemical characterization by polarization curves and visual observation was carried out to evaluate the anticorrosive behavior of the modified paints. The results showed that the corrosion rate determined from the tafel plot was lower in the steel samples covered with paint and polyaniline. The concentration of 0.8% of polyaniline in the paint showed a corrosion rate 12 times lower than that of the polyaniline-free paint. Additionally, visual observations and measurements of failed area carried out by applying an accelerated corrosion process by immersion in a 3.5% NaCl aqueous solution, allowed determining that, at a time of exposure of 300 h, corrosion inhibition can be achieved 26 times greater with the addition of 0.8% polyaniline. These results allowed to conclude that the addition of polyaniline by means of a simple mixture, significantly improved the anticorrosive protection capacity of a commercial epoxy paint.
Background: Composite materials make it possible to modulate the properties of the source materials and expand their technological potential. In this sense, composite materials made from solid biopolymeric electrolytes and graphene oxide can be an attractive alternative for applications in organic electronics due to their electrochemical properties. Aim: The present work aims to evaluate the electrochemical behavior of a composite material made of solid biopolymeric electrolyte of cassava starch and graphene oxide at different concentrations to determine the effect of this concentration and the pH used in the production process. Methods: The composite material was made from the use of cassava starch plasticized with glycerol, glutaraldehyde, polyethylene glycol and with lithium perchlorate as electrolytes. During the synthesis process, graphene oxide was added in different concentrations (0, 0.25, 0.50, 1.00, 1.25, 1.50, and 1.75 %w/w) to evaluate the effect of the concentration of this component. The synthesis was carried out by thermochemical method with constant heating in an oven at 75 ° C for 48 hours. Films were prepared using synthesis solutions at different pH (5.0 and 9.0). The pH was regulated by adding HCl or NaOH to the synthesis solution as appropriate. Results and Discussion: The results showed that the cassava starch biopolymeric solid electrolyte films without plasticizers were stiff and brittle, so they broke easily. The films with plasticizers and the films of the composite material were stable to the manual traction, allowing their easy manipulation without breaking. The films presented a similar electrochemical behavior in terms of oxide reduction processes; however, the films with graphene oxide presented signals with higher peak currents. Films made at pH 9.0 showed 50 % more intensity in peak currents. The addition of graphene oxide affected the current parameters and peak potentials, being more marked in the films prepared at pH 9.0; at this pH the films with concentrations of graphene oxide lower than 1.00 %w/w presented variable Ep and Ip, while at concentrations of graphene oxide greater than 1%w/w, the behavior did not show significant variations. Conclusions: The addition of graphene oxide modulates or modifies the electrochemical behavior of cassava starch biopolymeric solid electrolyte films, and the processing pH can vary the effect of the graphene oxide addition.
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