Macromolecules, Vol.32, No.17, 5552-5560, 1999
Raman spectroscopic characterization of association and thermoreversible gelation in aqueous systems of poly(N-acetamidoacrylamide)
Polymer self-association and thermoreversible gelation in aqueous solutions of poly(N-acetamidoacrylamide) (PAAA) have been investigated by Raman spectroscopy. We found that aqueous solutions of PAAA, even at low concentrations, revealed the presence of polymer-polymer coordination, suggesting formation of polymer clusters. The effect of denaturant (sodium thiocyanate) on the inter- and intramolecular interactions in the system has been also studied. It is shown that the SCN ions destroy the macroscopic hydrogen-bond network of water, as well as reduce the polymer's ability for self-association by occupying the NH groups. The changes observed in the Raman spectra upon the gel transition show that in the gel state the equilibrium of the system is shifted toward polymer-polymer coordination, whereas in the solution it is mostly polymer-water coordination. The influence of the different factors such as polymer concentration, level of denaturant addition, and type of solvent on the gel formation is discussed.
Keywords:TRANS-N-METHYLACETAMIDE;WATER-SOLUBLE POLYMER;HYDROGEN-BONDS;VIBRATIONAL ASSIGNMENTS;LIQUID WATER;UREA;SPECTRA;ENHANCEMENT;BEHAVIOR;STATE