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BORTOLIN, Adriel; AOUADA, Fauze A.; LONGO, Elson  and  MATTOSO, Luiz H. C.. Investigation of water absorption process in polysaccharide hydrogels: effect of ionic charge, presence of salt, monomer and polysaccharide concentrations. Polímeros [online]. 2012, vol.22, n.4, pp.311-317.  Epub Aug 07, 2012. ISSN 0104-1428.

This work reported the characterization of hydrogels constituted by methylcellulose (MC) entrapped in polyacrylamide (PAAm) network prepared by cross-linking polymerization (gelling process). Spectroscopic and morphologic properties were investigated using Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Effects of AAm, MC contents, ionic charge of salt counter-ions (NaCl, KCl, NH4Cl, CaCl2, MnCl2, MgCl2, and AlCl3), and fertilizers [(NH4)2SO4 and KH2PO4] on kinetic and hydrophilic (swelling degree) properties were investigated in detail. By decreasing the MC content or by increasing acrylamide content, there was a pronounced decrease in water uptake by the hydrogels. The increase in counter-ion X-Cl salt and the presence of fertilizer on the external swelling medium also provoked a decrease in water uptake. The water uptake mechanism of PAAm-MC hydrogels swollen in water followed the Fickian diffusion, while the mechanisms of hydrogels swollen in salt or fertilizer aqueous media followed the anomalous transport process. With their fast and high water absorption, the porous, three-dimensional matrices containing PAAm and MC are promising for agriculture as carrier vehicles.

Keywords : Water absorption; Fickian diffusion; biodegradable hydrogels; kinetic properties; morphologic properties.

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