1PA29 ^<13>C NMR分光法によるキラルスメクテック液晶のスピン-格子緩和時間測定

概要

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In order to investigate molecular rotation around its long axis in chiral smectic phases, temperature dependence of the spin-lattice relaxation time T_1 was measured in an antiferroelectric liquid crystal, (S)-4-(1-methylheptyloxycarbonyl)-phenyl 4'-octyloxybiphenyl-4-carboxylate ((S)-MHPOBC) by means of the solid-state ^<13>C 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 T_1 minimum occurs at ωοτ_c〜1, the correlation time τ_c of molecular motion should be on the order of 1/ωο〜10^<-8>s, with the Larmor frequency ωο of 100 MHz in the present measurements. In addition, the activation energies were estimated by the temperature dependence of T_1. 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.
日本液晶学会の論文
2001-09-24