Design and Synthesis of Thieno[3,2‐b]thiophene Derivatives Toward High‐Birefringence Materials for Microwave Application

A set of new liquid-crystalline compounds featuring a thieno[3,2-b]thiophene core was prepared to study how molecular structure influences both optical and dielectric characteristics. Determination of the mesomorphic properties of the synthesized compounds, along with the investigation of their optical and dielectric characteristics, allows for their characterization and classification as components of mixtures intended for microwave applications. The design of the structures was based on the functionalization of the heterocyclic thieno[3,2-b]thiophene core, which serves as the central core unit. They constitute a complement and a point of comparison with the previously presented structures exhibiting high birefringence and containing the thienothiophene ring. Optimization of the reaction conditions along the synthetic pathway to the final compounds allowed for diversification of the structures in terms of the type of terminal substituent, degree of fluorination, nature of the linking groups, and the length of the mesogenic core. The characterization of the obtained mesogens, explicitly designed for microwave applications, limited by the temperature range over which liquid crystalline properties are exhibited, indicates that the chosen research area represents a promising direction for the use of these materials as electrically controllable dielectric media for microwave applications.