Fourier transform infrared spectroscopy and X-ray diffraction studies of the molecular motions and structure changes of liquid crystal N-P-(Ethoxybenzylidene) p′-propylaniline (EBPA)

摘要

Highlights ? FT-IR measurements of EBPA have been performer in wide temperature range (not shown before in literature). ? 2D-correlation analysis and 2D moving window analysis for FT-IR spectra have been carried out for EBPA. ? The structures of solid phases have been identified by powder X-ray measurements. ? Phase transitions are of order-disorder type and are accompanied by ordering or arrangements of alkyloxy and alkyl chains. ? Irreversible phase transition (Cr3-N) has been detected during the first temperature treatment of the fresh sample. Abstract The results of X-ray and FT-IR spectroscopy studies of the N-P-(Ethoxybenzylidene) p'-propylaniline (abbreviated as EBPA) are presented. The structures of solid phases (Cr1, Cr2, Cr3) and temperature dependences of the unit cell parameters have been established on the basis of X-ray measurements. Irreversible phase transition Cr3–N between crystalline fresh sample (crystallized from solution without any thermal history) and nematic phase has been observed by X-ray method. Assignment of vibrational dynamics has been performed in isotropic, nematic and two crystalline phases with help of the DFT calculations. The two-dimensional (2D) correlation spectroscopy analysis shows changes in the conformational structure and specific interactions between molecules at phase transitions, mainly connected with ordering or specific rearrangements of alkyloxy chains. ]]>