Solid-state 13C NMR study of banana liquid crystals – 1: Two different alkyl tail-group packing environments in the B7 phase

Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed for the B7 phase of the banana-shaped molecule P-8-O-PIMB(NO2). In this phase, NMR chemical shifts assigned to five methylene carbons on the alkyl tail appear as at least seven peaks, indicating that the two alkyl tails within a single molecule have different packing structures. Combined CP/MAS and PST/MAS measurements show that one of the alkyl tails has dense packing with low molecular mobility and the other has loose packing with high molecular mobility. Thus, it can be concluded that both the polar bent and molecular axes are tilted toward the layer in the B7 phase of P-8-O-PIMB(NO2), exhibiting molecular leaning.

► Solid-state NMR measurements were performed for the banana-shaped molecule.
► NMR spectra show that the two alkyl tails have different packing structures.
► We concluded that both the polar bent and molecular axes are tilted in the B7 phase.