Crystal Structure and Polymorphism of Antiferroelectric Mesogen, 4-[(<i>S</i>)-1-Methylheptyloxycarbonyl]phenyl 4′-Octyloxybiphenyl-4-carboxylate (MHPOBC)

Abstract

Abstract Single crystal X-ray analysis has been carried out for the title compound, –COOCH(CH3)C6H13, which has antiferroelectric liquid crystalline phases. Crystal data; monoclinic, P21, T = 298 K, a = 32.285(7), b = 5.520(2), c = 9.320(2) Å, β = 95.34(2)°, V = 1653.7(7) Å3, Z = 2, dx = 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°) 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.