Molecular dynamics in a blue phase liquid crystal: a H-1 fast field-cycling NMR relaxometry study

Liquid crystals exhibiting Blue Phases (BPs) have been the focus of academic and commercial research interest in the last few years due to their highly interesting properties in the fields of optics and photonics. In order to better understand the properties of the BPs, it is important to study molecular dynamics in these phases, including molecular rotations/reorientations, diffusion, and collective motions. Here, we present the first study of molecular dynamics in a BP system by means of H-1 fast field-cycling relaxometry. The investigated sample, called 10BBL, was a lactate derivative, containing two chiral centers, exhibiting BP, TGBA*, TGBC*, and SmC* phases stable in rather large temperature ranges. Molecular dynamics was investigated by analyzing the temperature- and frequency-dependencies of spin-lattice relaxation. We compare the dynamics in the TGB phases with the one in the BP and with the TGB phases investigated in previous studies.