Relaxational behavior and swelling-pH master curves of poly[(diethylaminoethyl methacrylate)-graft-(ethylene glycol)] hydrogels

Poly[(diethylaminoethyl methacrylate)-graft-(ethylene glycol)] hydrogels were prepared with a molar ratio of 10:1 of diethylaminoethyl methacrylate to poly(ethylene glycol) of number-average molecular weights (Mn) 200, 400 and 1000 g mol−1 using tetra(ethylene glycol) dimethacrylate to give a crosslinking ratio between 0.5 and 4.0 %. Glucose oxidase and catalase were immobilized in the matrix during polymerization. The maximum enzyme loading used was 6.6 × 10−4 g of glucose oxidase per g of polymer. The equilibrium and dynamic swelling properties of these hydrogels were investigated. The pH-dependent equilibrium swelling characteristics showed a sharp transition between the swollen and the collapsed state at pH 7.0. The dynamic response of the hydrogel discs to pH was analyzed in pulsatile pH conditions. The effects of particle size, crosslinking and molecular weight of poly(ethylene glycol) (PEG) on the dynamic swelling response were investigated. The pulsatile nature of the response was analyzed using Boltzmann superposition. Swelling–pH master curves were obtained.  2004 Society of Chemical Industry