Molecular Rotation in an Antiferroelectric Liquid Crystal Studied by ¹³C-Nuclear Magnetic Resonance Spin-Lattice Relaxation Time Measurement

Abstract

Temperature dependence of the spin-lattice relaxation time T 1 was measured in an antiferroelectric liquid crystal, 4-(1-methylheptyloxycarbonyl) phenyl-4 ′ -octyloxybiphenyl-4-carboxylate (MHPOBC) by means of 13 C-nuclear magnetic resonance (NMR). The activation energies determined by the temperature dependence of T 1 are the same for most of the carbon nuclei in the SmA and SmC A * phases, whereas they are different for carbon nuclei at the chiral center and at the carbonyl carbons. The rotational correlation time changes continuously through the phase change from SmA to SmC A * . Critical slowing down of the molecular rotatioin was not observed.