CRYSTAL-STRUCTURE AND POLYMORPHISM OF ANTIFERROELECTRIC MESOGEN, 4-[(S)-1-METHYLHEPTYLOXYCARBONYL]PHENYL 4'-OCTYLOXYBIPHENYL-4-CARBOXYLATE (MHPOBC)

Single crystal X-ray analysis has been carried out for the title compound, [GRAPHICS] which has antiferroelectric liquid crystalline phases. Crystal data; monoclinic, P2(1), T=298 K, a=32.285(7), b=5.520(2), c=9.320(2) angstrom, beta=95.34(2)-degrees, V=1653.7(7) angstrom3, Z=2, d(x)=1.123 g cm-3. The crystal has a smectic-like layer structure composed of largely bent molecules; a chain of the chiral group is almost perpendicular (93-degrees) to the core moiety. DSC and temperature dependence of powder X-ray diffraction patterns show that the crystal is a metastable phase, which transforms to a more stable crystalline phase with longer spacing of layer.