FERROELECTRIC PHASE-TRANSITION OF THE DISUBSTITUTED DIACETYLENE 1,6-BIS(2,4-DINITROPHENOXY)-2,4-HEXADIYNE - ANALYSIS BY NMR AND X-RAY STUDIES

Proton-NMR and x-ray measurements were used to analyze the ferroelectric phase transition of the disubstituted diacetylene 1,6-bis(2,4-dinitrophenoxy)-2,4-hexadiyne (DNP), in which the phase transition is accompanied by a molecular twisting. Proton-spin-lattice relaxation is analyzed as function of Larmor frequency, temperature, and orientation of the single crystals. The molecular motions relevant for the dielectric phase transition and causing the loss of the center of symmetry of DNP single crystals are reflected by these NMR results and by detailed x-ray analysis at three different temperatures.