Microscopic Structures in Water-propylene Glycol Monoalkyl Ether Binary Mixtures as Clarified by NMR and Mass Spectrometry

Determination was made of the microscopic structures of binary mixtures of water and amphiphile (propyleneglycol-monomethylether (MPG) or propyleneglycol-monopropylether (PPG)) based on the NMR relaxation time (T1) of water and mass spectra of clusters isolated from solutions. The ratio of hydrating to non-hydrating water was derived from T1 and indicated water in MPG-water mixtures to be present more easily in the amphiphile hydration layer than in PPG-water mixtures. Hydrogen-bonded self-association clusters of MPG and PPG could be found in the aqueous solutions by mass spectrometry, the data from which showed MPG self-association clusters to undergo hydrogen bonding with water more readily than PPG self-association clusters. The results of NMR and mass spectrometry were found to be closely correlated. Microscopic structures and intermolecular interactions in aqueous solutions were accurately clarified.