¹H NMR relaxometry in the TGBA* and TGBC* phases

ABSTRACT

Recent results obtained by ¹H NMR relaxometry of liquid crystals having twist grain boundary (TGB) phases are here reviewed. In particular, three chiral rod-like lactate derivative mesogens were investigated. In the isotropic phase, three-exponential magnetization decay was observed in all cases and the three distinct spin-lattice relaxation times (T₁) were assigned to three specific molecular groups of these molecules. In the TGBA* and TGBC* phases the magnetization decay is mono-exponential and the main features of the ¹H NMR dispersion curves analyzed through a global target fitting procedure in terms of specific molecular and collective dynamics are discussed.

KEYWORDS:

• Ferroelectric liquid crystal
• chiral liquid crystals
• molecular dynamics
• nuclear magnetic resonance (NMR)
• twist grain boundary phases
• spin-lattice relaxation

Funding

This work was partly supported by the “Fast Field-Cycling NMR relaxometry study of chiral and non-chiral nematic liquid crystals” bilateral project Slovenia-Portugal. V. D. thanks the Centre of Excellence NAMASTE (Ljubljana) for the financial support as a visitor professor. The authors V. D., V. N. and V. H. thank the project ASCR M100101204 for partial support.