Hydrogen bonding in poly(maleic acid) upon charging: A solvent deuteron NMR and Fourier transform infrared study

The nuclear magnetic relaxation rates of deuterons in D2O solutions of poly (maleic acid) were studied as a function of charge. Under the assumption of fast exchange, the relaxation rates of deuterons on the carboxylate groups were calculated. The relaxation is shown to be driven by at least two proc esses, one having a correlation time much longer than the Larmor period and one much shorter. The contribution of the slow process shows a maximum aro und degree of neutralization alpha = 0.3, while that of the fast process is much smaller and vanishes between alpha = 0.4 and 0.5. FT-IR spectroscopy was used to determine the fraction of deuterons involved in hydrogen bondin g. The C=O stretching vibration is a measure of the amount of free GOOD gro ups on the polymer chain, from which the fraction of hydrogen-bonded carbox ylate groups is obtained. This fraction has a maximum at alpha approximate to 0.35.