Heliconical nematic and smectic phases: the synthesis and characterisation of the CB4O.m and CB8O.m series

Abstract

ABSTRACT The synthesis and characterisation of two series of nonsymmetric dimers belonging to the family of compounds, the 1-(4-cyanobiphenyl-4′-yl)-ω-(4-alkylanilinebenzylidene-4′-oxy)alkanes (CBnO.m) is reported; in the acronym, n refers to the number of carbon atoms in the spacer, and m in the terminal alkyl chain. The two series reported, CB4O.m and CB8O.m, both show twist-bend nematic (NTB) and smectic phases (SmCTB-SH and SmCTB-DH). Their phase behaviour is compared to that of the CB6O.m and CB10O.m series. For each series, locally intercalated molecular packing is observed for short terminal chains and interdigitated packing for long terminal chains. The intercalated anticlinic smectic CA phase is observed for the CB8O.m and CB10O.m series. All four series exhibit the SmCTB-SH and SmCTB-DH phases for the longer terminal chains and all have an interdigitated molecular arrangement. The absence of an intercalated heliconical phase is attributed to the high viscosity associated with the network intercalated structure.