The hydrogen bonding dynamics and cooperative interactions of DMAC–water mixture studied by dielectric relaxation spectroscopy

The dielectric constant for N,N-dimethylacetamide (DMAC)–water mixtures with entire mole fraction has been determined in the frequency range 20 MHz to 20 GHz at 298 K using the dielectric relaxation spectroscopy (DRS) method. A primary process with an asymmetric shape is observed. The mixture behaviour is described according to four Cole-Davidson terms whose evolution with composition is analysed. Numbers of hydrogen bonds between water–water and DMAC–water pairs are estimated from the values of the static dielectric constant by using the Luzar model. The model provides a satisfactory explanation of the experimental results related to the static dielectric constant. The hydrogen bond binding energies for water–water and DMAC–water are estimated to be −13.5 and −16.9 kJ mol−1; we also report a strategy to parameterise effective DMAC–water cluster interactions to provide valuable insights into the underlying mechanism of the relaxation acts.