Molecular Dynamics in Chiral Smectic Phases Investigated by ¹³C-NMR Spin Lattice Relaxation Time Observation

Abstract

The temperature dependence of the spin-lattice relaxation time T ₁ is investigated in a chiral smectic liquid crystal, (S)-(+)-2-methylbutyl 4-(4-decyloxybenzylideneamino)cinamate (S-DOBAMBC) by means of solid-state ¹³ C-NMR spectroscopy. T ₁ of aromatic carbon increases with increasing temperature for the temperature range of the SmA and SmC* phases, in which the frequency of the molecular rotation dominating the spin-lattice relaxation process is higher than the Larmor frequency ω ₀ of 100 MHz. In addition, the temperature dependence of T ₁ reveals that the activation energy of the molecular rotation in the SmC* phase is lower than that in the SmA phase.

Keywords:

• Ferroelectric liquid crystal
• ferroelectricity
• rotation
• molecular dynamics
• NMR
• smectic liquid crystals

Acknowledgment

We would like to thank Mr. Hideshi Hara for his assist to complete this paper. This work was supported by the “Academic Frontier” Project for Private Universities (2001-2005) and was partially supported by the Grant-in Aid for Scientific Research (#17550169): matching fund subsidy from the Ministry of Education, Culture, Sports, Science and Technology (MEXT).