Elucidation of the Water–DMSO Mixing Process Based on an IR Study

Abstract

The IR spectra of water–DMSO mixtures were recorded in the range of 0 < x < 1 DMSO mole fraction in the spectral region of 400–6000 cm−1. The combination and libration bands of water and the S = O band of DMSO were used to monitor changes in the system. The combination and libration bands of water were analyzed in terms of different degrees of connectivity of water molecules. Two types of complexes differing by their water–DMSO ratio and the nature of water participating in their formation were found in the mixture. Complex I involves large water clusters stabilized by DMSO molecules and gradually diminishing in their size with increasing DMSO content. Water molecules separated from the bulk water interact with DMSO to form complex II. The water clusters were shown to exist in the mixture up to 90 mol% DMSO. The inertness of the inner molecules of the water cluster is the reason of the begining of DMSO accumulation at the notable water excess.