Unusual Increase of Apparent Transverse Relaxation Times in NMR Profiling of a Drying Polymer Solution

Abstract

In this contribution, we present results from a nuclear magnetic resonance (NMR) profiling study of drying polymer solutions using polyvinylpyrrolidone (PVP) as a model system. The careful evaluation of the experimental data reveals a surprising increase in the apparent transverse relaxation time of the water phase of the drying solution over the first few hours of drying (where usually a decrease would be expected). By using additional information obtained from diffusion-weighted profiles, we can explain this finding as the result of a strong reduction of the diffusion effect on the apparent relaxation time during this time interval. Understanding this effect provides a better basis for making optimal use of profiling NMR in drying studies and avoids possible misinterpretation on the data.