A dielectric relaxation study of self and heteroassociation in binary liquid mixtures of three pyrrolidinones with alcoholes and water

Nine binary mixture systems AB are considered, where A = 2‐pyrrolidinone, N‐methyl‐2‐pyrrolidinone or N‐cyclohexyl‐2‐pyrrolidinone and B = water, methanol or ethanediol. Their complex permittivity, as measured in the 20 MHz to 36 GHz range at 20°C, is interpreted by a model supported analysis. It applies in particular an empirical correlation between relaxation time and viscosity as established for the case of rigid molecules, relaxing by rotational tumbling. From this, constraints are obtained for those spectral components which are due to species of that category. The procedure yields, among others, for any system a spectral component which can be ascribed to heteroassociates of probably definite AB or AB 2 composition. Again with any system, self association of B type molecules is observed, which is strongly affected by addition of A. Special relaxation features of some substances are also considered.