Contribution of proton NMR relaxation to the investigation of molecular dynamics in columnar mesophases of discotic and polycatenar molecules

摘要

We present in this work a review concerning wide frequency range T_1 proton NMR relaxation studies performed in compounds exhibiting columnar mesophases, namely the Col_(ho) mesophase in the case of a liquid crystal of discotic molecules and the φ_h mesophase in the case of a liquid crystal of biforked molecules. These NMR relaxation studies were performed combining conventional and fast field cycling NMR techniques in a frequency range between 100 Hz and 300 MHz. The possibility of probing such a large frequency range has provided a way to effectively distinguish the influence, on the T_1 relaxation profiles, of the different molecular movements observed in this type of mesophases. In addition, we present a comparison between the molecular dynamics in columnar (φ_n) and lamellar (SmC) mesophases exhibited by the same biforked compound.