Antiferroelectricity in achiral mesogenic mixtures of organic materials

Artículo de publicación ISITo clarify the mechanism involved in the appearance of antiferroelectric properties in mixtures of polymers containing achiral mesogenic side chains and their monomers, X-ray investigation was carried out in pyroelectrically active samples. The thermal stability of such systems is also reported. The X-ray investigation shows that in highly concentrated mixtures of monomer in polymer, a segregation of the excess of monomer from an optimized ratio (33% monomer/polymer) occurs

Dihydropyridine-fused and pyridine-fused coumarins: Reduction on a glassy carbon electrode in dimethylformamide

In this study, two series of dihydropyridine-fused and pyridine-fused coumarins were synthesised and electrochemically characterised in aprotic medium. In both series, the most easily reducible groups were the endocyclic carbonyl groups. The electrochemical mechanism for both types of compounds is strongly dependent on the experimental time-scale. Cyclic voltammetric (CV) reduction on a glassy carbon electrode (GCE) of the endocyclic carbonyl group of dihydropyridine-fused coumarins involves an ECEC mechanism with two electron transfer steps that are coupled with chemical reactions to produce the corresponding hemiacetal derivative. In the case of pyridine-fused coumarins, CV reduction of the endocyclic carbonyl group involves an EEC mechanism. ESR studies revealed the presence of a stabilised intermediate only for the pyridine-fused derivatives. Our theoretical study showed a spin density map of radical species delocalised mainly within the coumarin ring, indicating the reduction of