X-RAY STRUCTURE ANALYSES AND VIBRATIONAL SPECTRAL MEASUREMENTS OF THE MODEL COMPOUNDS OF THE LIQUID-CRYSTALLINE ARYLATE POLYMERS .2. STRUCTURAL ISOMORPHISM IN A SERIES OF MODEL COMPOUNDS

X-ray structural analysis has been done for the model compounds of liquid-crystalline arylate polymers, Et-OCO-Ph-OCOPh(n)COO-Ph-COO-Et. The crystal structure data of the compound with n = 1 are as follows at room temperature: monoclinic, P2(1)/c-C2h,5 a = 25.430 (9) angstrom, b = 5.4435 (6) angstrom, c = 8.282 (2) angstrom, beta = 97.63 (3)-degrees, Z = 2, R = 0.064. The structure and packing fashion of the molecules of the n1 crystal were found essentially isomorphous to those of the beta form of the n2 crystal. The X-ray diffraction and infrared and Raman spectral patterns of the n3 compound are very similar to those of the n1 and n2-beta crystal forms, making it possible to estimate the crystal and molecular structures of this compound. From the temperature dependence of the X-ray reflection, the anisotropic thermal expansion coefficients were evaluated for these three compounds. They were found to be similar to each other among these compounds, being supported by a direct optical microscopic observation of the dimensional change of the single crystals.