Competing synclinic and anticlinic interactions in smectic phases of bent-core mesogens

Abstract

Recent studies on liquid crystals (LCs) have focused on structurally new molecular systems forming phases distinct from simple nematic or smectic ones. Sophisticated molecular shapes may reveal structural complexity, combining helicity and polarity. Mirror symmetry-breaking in bent-core molecules can lead to a propensity for synclinic and anticlinic molecular structures within consecutive smectic layers. On the other hand, despite their achiral character, dimers readily adopt helical phases. In this study, we investigate a hybrid molecular structure incorporating both characteristics, namely a rigid bent-core and an attached bulky polar group via a flexible spacer. To perform phase identification, we enrich standard experimental methods with sophisticated resonant soft X-ray scattering technique. Notably, we observe a distinct preference for specific phase types depending on the length of the homologue. Longer homologues exhibit a predisposition towards the formation of tilted smectic phases, which are characterized by complex sequences of synclinic and anticlinic interfaces. Conversely, shorter homologues demonstrate a propensity for helical smectic structures. For intermediate homologues, the frustration is alleviated through the formation of several modulated smectic phases. On the basis of the presented study, we describe the preconditions for high-level structures in relation to conflicting constraints.