Semi-IPNs of starch and poly(acrylamide-co-sodium methacrylate): Preparation, swelling and diffusion characteristics evaluation

Semi-interpenetrating polymer network (IPN) hydrogels composed of starch and random copolymer of poly(acrylamide-co-sodium methacrylate) [poly(AAm-co-NMA)] were prepared by polymerizing an aqueous solution of acrylamide (AAm), sodium methacrylate (NMA) using ammonium persulphate (APS)/N,N,N-1,N-1-tetramethylethylenediamine (TMEDA) as redox initiating system in presence of a crosslinker and starch solution. IR spectroscopy was used to identify the presence of different repeating units in the IPN networks. The swelling and diffusion characteristics, such as initial swelling rate (r(i)), swelling rate constant (k(s)), equilibrium swelling ratio (S-eq), diffusion constant (n) and diffusion coefficients (D) were evaluated for different semi-IPN hydrogels prepared under various formulations. For better understanding of network structure formation of these semi-IPNs, three different crosslinkers namely, N,N-methylenebisacrylamide (MBA), 1,4-butanediol.diacrylate (BDDA) and diallyl phthalate (DP) were employed. Further, the swelling pattern of semi-IPN hydrogels was studied in different physiological, pH and ionic/salt solutions and showed great responsiveness due to their ionic character. The morphological features of these IPNs were observed using scanning electron microscopy (SEM). (c) 2006 Elsevier B.V. All rights reserved.