STUDY OF STRUCTURAL ORGANIZATION OF SYSTEMS ON BASIS OF p-n-PROPYLOXICINNAMIC ACID AND NONMESOGENES OF Ph–X–Ph TYPE

Abstract

The variants of structural organization in the systems “mesogen – nonmesogen” are considered. The systems contain p-n-propyloxycinnamic acid (A), as a mesogenic component, and nonmesogenic Ph–X–Ph compounds: phenyl benzoate (B, where X = –COO–), azobenzene (C, where X = –N=N–) and N-benzylideneaniline (D, where X = –CH=N–). Quantum-chemical modeling of possible structural units in such systems has been performed. It was shown that all assumed A∙∙∙X(Ph)2 H-complexes do not have electronic and geometric anisotropy and have a lower intermolecular interaction energy than the cyclic dimer of acid A∙∙∙A. The calculated values of the Gibbs free energy of complexation reactions also indicate a low probability of the formation of A∙∙∙X(Ph)2 type H-complexes. It is noted that the “length” of the A∙∙∙A dimer is comparable with the doubled “length” of Ph–X–Ph molecules, which, like the acid dimer, have a rod-like structure favorable for the formation of nematic and smectic LC phases. Based on the analysis of the quantum chemical calculations, it was assumed that Ph–X–Ph can be embedded between acid cyclic dimers A∙∙∙A and can facilitate reduce intermolecular interactions in the system, which reduces the temperature of Cr–LC transitions. The proposed structural organization of systems A: Ph–X–Ph is confirmed by an experimental IR spectrum for a similar system, in which the bands corresponding to the vibrational frequencies of the acid dimer and to individual molecules of alkyloxy substituted phenyl benzoate B are recorded.