Synthesis of soluble, air-stable fully conjugated ladder polymers

Abstract

Herein, we report the synthesis of soluble, air-stable fully conjugated ladder polymers incorporating a BTBT structure as a repeating unit. The ladder polymers were synthesized through a simple process: A Migita-Kosugi-Stille polycondensation, followed by an intramolecular oxidative C–H annulation (Scholl reaction). Absorption and fluorescence spectrometric analyses, as well as theoretical analysis and model reaction revealed that the intramolecular Scholl reaction proceeded efficiently. Electrochemical studies combined with theoretical molecular orbital analysis indicated that the resultant ladder polymers are stable under ambient conditions, because the drastic ascension of the highest-occupied molecular orbital (HOMO) level was suppressed even after ladderization by the Scholl reaction. Furthermore, the bottom-gate top-contact organic thin-film devices that were fabricated from these ladder polymers operated as solution-processable p-type transistors.