Efeito Do Ph, Espécie E Concentração Iônica Na Absorção De Água De Hidrogéis Bionanocompósitos Constituídos De CMC/Paam/Laponita RDS

Abstract

Recebido em 23/01/2019; aceito em 13/05/2019; publicado na web em 20/08/2019 EFFECT OF PH, IONIC CONCENTRATION AND SPECIES ON THE ABSORPTION OF WATER BY HYDROGEL BIONANOCOMPOSITS CONSTITUTED FROM CMC/PAAm/ LAPONITE RDS. The objective of this paper was to study the effect of pH, concentration and ionic species on the water absorption of the bionanocomposite hydrogels based on carboxymethylcellulose polysaccharide and laponite nanoclay. Bionanocomposite hydrogels were obtained via free radical polymerization. It was possible to observe that the swelling degree (Q) and kinetic properties were strongly influenced, and controlled, by the presence and quantity of ionic species, decreasing their water uptake when compared to the same values obtained in distilled water. Furthermore, the addition of nanoclay decreased the water uptake sensibility of the hydrogel in ionic media. It was also observed that the presence of the nanoclay decreased the Q eq distilled water values from 32.5 g g-1 to 22.5 g g-1. The pKa variation of the bionanocomposites was a good indication of the possible interaction of the nanoclay-polymeric chains. The possibility of the control of water absorption (velocity and quantity) whereas these nanocomposites are pH-and salt-responsive may potentiate their application in agriculture. Agronomical studies are in progress, which can confirm its applicability in this area.

Polyacrylamide hydrogels prepared by varying water content during polymerization: Material characterization, reswelling ability, and aging resistance

“…This behavior was observed for instance for poly(ethylene glycol) diacrylate and its nanocomposites with laponite, [53] or for carboxy-methylcellulose/PAAm copolymer and its nanocomposites with laponite. [54] Moreover, solutions of multivalent salts provide stronger shrinking than those of monovalent salts. [55,56] The action of osmotic pressure, that is, moving of water from hydrogel to surrounding medium with higher salt concentration, provides a plausible explanation for this phenomenon.…”