Microscopy studies of the nematic NTB phase of 1,11-di-(1′′-cyanobiphenyl-4-yl)undecane

Abstract

A detailed microscopy study of the mesophases of 1,11-di-(1′′-cyanobiphenyl-4-yl)undecane (CB11CB) was undertaken, with an emphasis on attempting to relate the recent helical “twist-bend” model of the N_TB phase to the observed optical textures. Our ability to draw a freestanding film indicates that the phase is unlikely to be nematic and possesses long range periodicity. No electrooptic response could be detected in the N_TB phase, with or without addition of a chiral dopant although dielectric breakdown and space charge were observed at high voltage leading to field dependent pulsing of the sample. No optical rotation associated with a macroscopic helical structure could be discerned in the N_TB phase. However, this observation could be taken to be in keeping with the extremely short pitch of a proposed “twist-bend” model.