title: Molecular geometry, twist-bend nematic phase and unconventional elasticity: a generalised Maier-Saupe theory.
abstract: It has been found that bent-shaped achiral molecules can form a liquid crystal phase, called the Twist-Bend Nematic (NTB), which is locally polar and spontaneously twisted having a tilted director, with a conglomerate of degenerate chiral domains with opposite handedness and pitch of a few molecular lengths. Here, using a major extension of the Maier-Saupe molecular field theory, we can describe the transition from the nematic (N) to the NTB phase. We provide a consistent picture of the structural and elastic properties in the two phases, as a function of the molecular bend angle, and show that on approaching the transition there is a gradual softening of the bend mode in the N phase. This points to the crucial role of the molecular shape for the formation of modulated nematic phases and their behaviour.
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Padova, via Marzolo 1, 35121 Padova, Italy. alberta.ferrarini@unipd.it cristina.greco@studenti.unipd.it.
authors.forename: Cristina
authors.initials: C
authors.lastname: Greco
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Luckhurst
authors.forename: Alberta
authors.initials: A
authors.lastname: Ferrarini