Water sorption behaviour of highly swelling (carboxy methylcellulose-g-polyacrylamide) hydrogels and release of potassium nitrate as agrochemical

Novel types of highly swelling hydrogels have been prepared by grafting crosslinked polyacrylamide chains onto carboxymethylcellulose (CMC) via a free radical polymerization method. The hydrogels were characterized by IR spectral analysis and by evaluating various network parameters such as average molecular weight between crosslinks (M-c), crosslink density (q) and the number of elastically effective chains (V,,). The hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics which were highly dependent on the chemical composition of the hydrogel and pH and ionic strength of the medium in which the hydrogel was immersed. The kinetics of water uptake and the water transport mechanism were studied as a function of the composition of the hydrogel and the pH of the medium. The hydrogels were also loaded with potassium nitrate as a model agrochemical and their potential for controlled release of potassium nitrate was judged by measuring conductivity. Various kinetic parameters such as the diffusion coefficient and swelling exponents were also calculated. (C) 2003 Elsevier Science Ltd. All rights reserved.