Novel water-swollen photo-crosslinked membranes were obtained by copolymerization of the N-vinylpyrrolidone, butyl acrylate and ethyl methacrylate monomers functionalized with naphthalimide groups, as pH sensitive fluorescence probes. For that purpose, two monomers with pending naphthalimide groups anchored to ethyl methacrylate through alkyl chains with different length, were previously synthesized. The membranes were characterized using different techniques. The pH dependence of absorbance and the corresponding quenching of fluorescence were investigated and related to the structure of naphthalimide substituents linked to the membrane. The new solid sensors exhibited sensitive fluorescence changes at pH < 3, and lower time response was determined for membranes where the sensing group was linked through longer alkyl chain to the polymer matrix. The membranes were solid, thermally stable and easily handled to be applied as sensor materials, and showed a reversible behavior, which is an important feature for further fabrication of an economical on-site tool for the acidity detection in aqueous environments.
RESUMENEste trabajo presenta el efecto que produce la adición de dispersión acuosa de mucílago de nopal y el extracto de algas marinas cafés en el grado de hidratación de pastas de cemento Portland ordinario. Se elaboraron pastas de cemento con relaciones agua/cemento de 0.30 y 0.60, conteniendo los aditivos naturales en tres concentraciones. Las pastas se curaron en húmedo y selladas. Se determinó el grado de hidratación de las pastas ignición y análisis termo-gravimétrico a los 14, 28 y 56 días de edad. Los resultados indican un mayor grado de hidratación en las pastas de cemento con relación agua/cemento de 0.60 conteniendo los aditivos naturales en comparación con el control. Se sugiere que esto es debido a una mejor dispersión de las partículas de cemento en la presencia de estos aditivos y a la capacidad de estos para retener agua, con lo cual se produce curado interno.Palabras claves: Mucílago de nopal; Extracto de algas cafés; Grado de hidratación; Análisis termogravimétrico. ABSTRACTThis paper presents the effect produced by the addition of aqueous dispersions of cactus mucilage and brown seaweed extract on the degree of hydration of ordinary Portland cement pastes. Cement pastes with water/cement ratios of 0.30 and 0.60 were prepared containing the natural additives at three concentrations. The curing conditions were moist cured and sealed. The degree of hydration was determined by ignition and thermo-gravimetric analysis at 14, 28 and 56 days of age. The results indicate a higher degree of hydration in pastes with a water/cement ratio of 0.60 containing the natural additives with respect to control specimens. This effect could be explained by a better dispersion of cement particles in the presence of the natural additives and their capacity to retain water, thereby providing internal curing.
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