In this study, the effects of introduction of lithium perchlorate into polyacrylamide hydrogels having constant amounts of acrylamide monomers and N,N＇-methylene-bis-acrylamide crosslinker have been studied through the observed changes in the vibrational Raman spectra. The changes in the perchlorate anion＇s Raman modes show that in the polymeric matrix most of the lithium and perchlorate ions are separated by the polyacrylamide coils. The changes in the Raman modes of the polymeric chains show that the interactions of the two ionic species with the coils are unfavourable to the hydrogen-bond network of the hydrogel matrix. As the amount of lithium perchlorate in the hydrogel increases the role played by the intra and inter-molecular hydrogen bonds due either to the amide groups or the interstitial water decreases; the amide groups become more accessible to chemical transformations and the hydrogel flexibility increases. (C) 2000 Elsevier Science Ltd. All rights reserved.