Thieno[3,2-b]thiophene derivatives exhibiting semiconducting liquid-crystalline phases at lower temperatures

Abstract

We synthesized novel liquid crystalline semiconductors bearing an extended π-conjugated mesogen based on thieno[3,2-b]thiophene, which exhibit high solubility and low phase transition temperature. In particular, lateral methyl substitution to the mesogenic unit led to the formation of efficiently self-organized LC domains at lower temperature than that of reported liquid crystalline thieno[3,2-b]thiophene derivatives. Smectic A and smectic E phases were observed by a polarizing optical microscope over a wide temperature range between 75 and 125 °C. Hole mobility was determined by the time-of-flight (TOF) method, and calculated up to 2 × 10⁻³ cm² V⁻¹ s⁻¹. Herein we report the synthesis, thermophysical and carrier transport properties of novel thieno[3,2-b]thiophene based liquid-crystalline semiconductors.