Synthesis and liquid crystalline properties of novel laterally connected trimesogens and tetramesogens

Abstract

Three types of laterally connected triplet mesogens and one quadruplet mesogen incorporating rigid p-terphenyl units have been synthesized. Their liquid crystalline behaviour was investigated by polarizing microscopy, differential scanning calorimetry and X-ray scattering. The lateral fixation of three rod-like 4,4″-didecyloxy-p-terphenyl units mostly gives liquid crystalline materials with considerably increased mesophase stabilities with respect to the parent 4,4″-didecyloxy-2′-methyl-p-terphenyl. The mesophase stability strongly depends on the type of connection. The highest clearing temperatures were observed for triplets which are connected in line with each other (type I) and triplets which are laterally connected in a peripheral manner. Only the oligomesogens of type III are not liquid crystalline. All compounds incorporating exclusively decyloxy chains exhibit smectic phases (S_A and S_c). For the ethoxy derivatives the nematic phase was found.