THE ELASTIC BEHAVIOR OF HYDROGELS

The mechanical properties and the swelling behavior of aqueous poly(acryl amide) and poly(acryl amide-co-Na acrylate) gels were investigated. The ionic networks were prepared by hydrolysis of the non-ionic ones, in this way preserving the network topology. By measurement of the modulus it was detected that networks prepared in solution contain a rather large portion of elastically ineffective rings. Hydrolysing a part of the amide groups resulted in a considerably increased swelling ratio. The modulus of such ionic gels did not show the predicted decrease with rising swelling ratio, but on the contrary increased up to a fivefold value.