Chitosan-Graft-Polyacrylamide Based Release Systems: Effect of pH and Crosslinking

This study covers the synthesis and release behavior of chitosan-graft-polyacrylamide copolymers in aqueous media at different pH values. The copolymers were synthesized using redox polymerization with ceric ammonium nitrate (CAN) in 1% aqueous acetic acid solution as the initiator. Optimum condition for the graft copolymer synthesis was determined as 3.85 g/L chitosan, 0.27 M acrylamide (AAm) monomer at 40 °C with a CAN per gram chitosan as 6 mmol using 0.05 M stock solution in 0.1 N HNO3. Then the crosslinked copolymers were synthesized using methylenebisacrylamide (MBA) as a crosslinker varying mass proportions of AAm:MBA as 15:1, 20:1, and 30:1. Obtained material amount (polymer yield) and molecular weight of crosslinked copolymers were lower than the graft copolymer as expected. Acetylsalicylic acid (ASA) release behaviors of all copolymers were monitored with UV-visible spectroscopy at different pH values (2, 6, and 8.5) corresponding to different media in the body (stomach, skin, and intestine, respectively). According to the results, the release behavior changed the least among the samples with respect to medium pH and of was the most affected.