THE EFFECT OF EXTERNAL STIMULI ON THE EQUILIBRIUM SWELLING PROPERTIESOF POLY(N-VINYL 2-PYRROLIDONE ITACONIC ACID) POLYELECTROLYTE HYDROGELS

Hydrogels with varying crosslink densities and ionic moieties were pre pared from the ternary systems N-vinyl 2-pyrrolidone/itaconic acid/wat er by irradiation with gamma rays at ambient temperature. The influenc e of external stimuli such as pH, temperature and ionic strength of th e swelling media and the type of buffer on the equilibrium swelling pr operties were investigated. Hydrogels showed typical pH response and t emperature responses, such as high-pH and low-temperature swelling and low-pH and high-temperature deswelling. A change in the ionic strengt h of the swelling solution from 0.01 to 0.20 caused a decrease in the equilibrium degree of swelling of hydrogels. Oscillatory swelling beha viour was also observed and investigated in response to changes in the pH of the solution. (C) 1998 Elsevier Science Ltd. All rights reserve d.