抄録
In order to investigate molecular rotation around its long axis in chiral smectic phases, temperature dependence of the spin-lattice relaxation time T1 was measured in an antiferroelectric liquid crystal, (S)-4-(1-methylheptyloxycarbonyl)-phenyl 4'-octyloxybiphenyl-4-carboxylate ((S)-MHPOBC) by means of the solid-state 13CC NMR spectroscopy. In its temperature dependent curve, T_1 of the phenyl core part has had a minimum at the temperature region of the SmCA^* phase. Since T1 minimum occurs at ωοτc〜1, the correlation time τc of molecular motion should be on the order of 1/ωο〜10-8s, with the Larmor frequency ωο of 100 MHz in the present measurements. In addition, the activation energies were estimated by the temperature dependence of T1. Activation energies in the SmCA* phase are larger than that in SmA for most of the carbon nuclei of the phenyl core part, because molecular rotation is hindered in the SmCA* phase.
