Release kinetics and diffusion coefficients of solid and liquid pesticides through interpenetrating polymer network beads of polyacrylamide-g-guar gum with sodium alginate

Grafting of acrylamide onto guar gum is achieved by Ce(IV) induced free-radical polymerization to prepare interpenetrating polymer network (IPN) beads of polyacrylamide-g-guar gum with sodium alginate by crosslinking with glutaraldehyde. Two widely used pesticides, solid chlorpyrifos and liquid fenvelarate, are loaded up to 60–70% efficiency in the IPN beads. The polymer and beads are characterized by Fourier transform IR spectroscopy to confirm grafting and to understand the possible interactions between the pesticides and the polymer matrix. Scanning electron microscopy is used to study the morphology of the beads. Equilibrium swelling experiments indicate that the swelling of the beads decreases with an increase in crosslinking, as well as an increase in pesticide loading. The in vitro release studies are performed under static conditions, and the release data are fitted to an empirical relationship to evaluate the transport parameters. Diffusion coefficients are calculated for the transport of pesticides through the polymeric beads using the initial and later time approximation methods. These values show a decrease with increasing crosslinking and increasing pesticide loading. Long-term diffusion coefficients as computed by Fick's equations are found to be smaller in magnitude when compared to the initial time diffusion coefficients. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 451–457, 2003