Chirality and Molecular Dynamics of Smectic Compound Studied by ¹³C-NMR Spin-Lattice Relaxation Time Observation

Abstract

The temperature dependence of the spin-lattice relaxation time T ₁ is investigated in the racemic mixture of a smectic liquid crystal, 4-(1-methylhexyloxycarbonyl)phenyl 4′-octyloxybiphenyl-4-carboxylate ((±)-MH(6)POBC) by means of solid-state ¹³ C-NMR spectroscopy. T ₁ of almost all of aromatic carbons has a minimum at the smectic C (SmC) temperature region, because the frequency of the molecular rotational motion corresponds to the Larmor frequency of 100 MHz in the present measurements. In addition, analysis of the temperature dependence of T ₁ reveals that the activation energy of the molecular rotation in the SmC phase is higher than that in the SmA phase.

Keywords:

• Chirality
• ferroelectric liquid crystal
• hindered rotation
• molecular dynamics
• NMR
• smectic liquid crystals
• spontaneous polarization

Acknowledgment

This work was supported by the Grant-in-Aid for Scientific Research (#17550169) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT). This work partially supported by the “Academic Frontier” Project for Private Universities (2006-2008), matching fund subsidy from MEXT.