STRUCTURE OF SOME MESOGENIC CHIRAL AND ACHIRAL ACRYLATES AND THEIR MIXTURES ACCORDING TO X-RAY DATA
X-ray diffraction method was used to study the structure of mesogenic chiral and achiral acrylates (disubstituted biphenyl and phenyl benzoate) and their mixtures under the orienting influence of a magnetic field. Diffraction patterns were analyzed using the Hosemann model of a paracrystal. Structural modeling and diffraction calculations on models were used to determine the parameters of layer structures. X-ray diffraction data of all phase states of mesogenic acrylates and their compositions with different ratios of chiral and achiral components were obtained and analyzed. Chiral and achiral acrylates in the crystalline state form monoclinic lattices with polar symmetry (space groups P21 and P2, respectively). In both structures, the "head - tail" packing of molecules is implemented. In the structure of chiral monomer, the transverse dipole moments of molecules associated with C=O groups are compensated due to steric factor. The achiral acrylate molecule has a total transverse dipole moment less than 1 D due to the off-orientation of the dipole moments of C=O groups. The polar crystal structure of the chiral acrylate, when heated, changes into helicoidal SmF* structure, in which the compensation of dipole moments is preserved. The polar crystal structure of achiral acrylate forms non-polar liquid crystal SmA and N structures. In mixed compositions of the chiral and achiral acrylates, phase separation is observed only in the crystalline samples with a high content of the chiral component. Chiral SmF* and SmC* structures are formed in samples with high content of the chiral component but without phase separation. In these phase structures, we can expect the weakening of steric factor influence on the compensation of transverse dipole moments of the chiral molecules.