Raman Spectroscopic Characterization of Association and Thermoreversible Gelation in Aqueous Systems of Poly(N-acetamidoacrylamide)

Abstract

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.

Raman spectroscopy and multivariate analysis for the rapid discrimination between native-like and non-native states in freeze-dried protein formulations

“…10A there were also differences between NL and DEN samples in the spectral regions related to some amino acid side chains, i.e. the bands 1320-1500 cm -1 , and near 1130 cm -1 and 1070 cm -1 [35,43]. This matches again with the variables indicated by the loading and discriminant vectors.…”

Comparative Vibrational Spectroscopy of Intracellular Tau and Extracellular Collagen I Reveals Parallels of Gelation and Fibrillar Structure

“…Last, the disappearance of the amide bands with dissolution of the 5-year-old tau gel by the addition of a high concentration of lithium thiocyanate (Fig. 1d), which is known to disrupt water structure (35), further supports this interpretation.…”

“…1, spectrum b, where the 1616-cm Ϫ1 peaks were normalized before spectral subtraction. The addition of lithium thiocyanate (final thiocyanate concentration ϭ 3 M), a known disrupter of water structure (35), to the cured tau 2-19 gel yields a noncloudy liquid, implying tau dissolution. The UVRR spectrum for the thiocyanate solution of the cured tau 2-19 gel is given in Fig.…”

Non‐Ionic Homo‐ and Copolymers with H‐Donor and H‐Acceptor Units with an UCST in Water

“…They concluded that the crosslinking is based on randomly distributed hydrogen bonds. More recently this was supported by dynamic light scattering and Raman spectroscopy 12, 13…”