Synthesis and swelling characteristics of semi-interpenetrating polymer network hydrogels composed of poly(acrylamide) and poly(γ-glutamic acid)

The swelling behaviours of semi-interpenetrating polymer networks (semi-IPNs) composed of poly(acrylamide) (PAAm) and poly(γ-glutamic acid) (γ-PGA) in water were investigated. The PAAm/γ-PGA semi-IPNs having different molar composition were synthesized by free radical polymerization of acrylamide in the presence of γ-PGA obtained from Bacillus licheniformis bacterium. The swelling behaviours of these semi-IPNs were analysed in buffer solutions at various pH (3, 5, 7 and 10) and two temperature ranges (25 and 37 °C). Swelling rates of all semi-IPNs were relatively high, and they showed sensitivity to both pH and temperature. Maximum values of swelling rates were reached in the range of 33–38 when pH, temperature and poly(γ-glutamic acid) content increase.