Dielectric and pyroelectric properties of single crystals of 1,6-bis(2,4-dinitrophenoxy)-2,4-hexadiyne (DNP) were measured parallel to the polar b axis. Poling experiments with static electric field strengths of up to 33 kV cm-1 prove that, at least for parts of the crystals, the direction of the spontaneous polarization can be reversed, implying a distribution of transition temperatures. The maximum polarization measured reveals values up to 2.4*10-7 C cm-2 at 10 K, which is in very good agreement with X-ray studies. Within a Landau theory of phase transitions for ferroelectric materials, the experimental curves of the spontaneous polarization seem to behave tricritically in the polar phase below 46 K. Owing to the distribution of transition temperatures, the order of the phase transition cannot be determined from permittivity experiments. The influence of a small static electric field on the electric susceptibility is discussed as well.
The synthesis of two new asymmetrical diacetylene (DA) derivatives is described: 1‐(4‐fluorobenzenesulfonyloxy)‐6‐(4‐trifluoromethylbenzenesulfonyloxy)‐2,4‐hexadiyne (FBS/TFMBS) and 1‐(2,4‐dinitrophenoxy)‐6‐(4‐methyl‐2‐nitrophenoxy)‐2,4‐hexadiyne (DNP/MNP). Results are presented on crystal growth, crystal structure analysis and dielectric properties. Both DAs polymerize thermally in the solid state and have polar (“ferroelectric”) individual chains. The different chains in the unit cell are arranged centrosymmetrically in FBS/TFMBS, but non‐centrosymmetrically in DNP/MNP.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.