Observing Solid–Solid Phase Transitions in Two Alkanes and Natural Wax with Multidimensional NMR Relaxometry

Abstract

Nuclear magnetic resonance (NMR) spin–spin T₂ relaxation is applied to characterize structural rearrangements in solid–solid phase transitions of lipids. 1D T₂ relaxation distributions as a function of temperature indicate solid–solid transitions not easily discernible by differential scanning calorimetry (DSC). T₂–T₂ correlation exchange measurements are demonstrated to be sensitive to spin-diffusion, allowing measurement of morphological length scales related to solid–solid molecular structure rearrangement by NMR relaxometry. T₂ dispersion distributions indicate radio frequency pulse separation time dependence which alters with morphology and temperature. The NMR relaxometry data are complementary to DSC and has potential for bench top low field NMR implementation.