Orientational entropy and dipolar aggregation in mixtures of propylene carbonate + N , N -dimethylacetamide

The analysis of temperature behavior of the orientational entropy increment induced by the probing electric field, has been performed for two strongly polar liquids: propylene carbonate (PC) and dimethylacetamide (DMA), in the neat states as well as mixed together. It has been found that in the both neat fluids, the molecular dipoles self-assemble in a parallel, the head-to-tail way, wherein the effect is significantly higher in a less polar dimethylacetamide. This proves a better structural adjustment of DMA molecules to their effective self-association. In the mixtures of these two self-assembled liquids, the mixed dipolar aggregates consisting of molecules PC and DMA occur, in contrast to the mixtures of PC + DMSO (dimethyl sulfoxide), where the highly polar molecules of DMSO, being not capable for self-association, play only a neutral role of the filler the space between assemblies composed of PC molecules. The residual electrical conductivity in mixtures under investigation has been characterized.