Isoquinoline-1,3-dione-derived conjugated polymers for field-effect transistors: synthesis, properties, and the effect of inner aromatic bridges

Abstract

Isoquinoline-1,3-dione (IQD) is a novel electron-withdrawing building block. However, its polymer derivatives have been rarely constructed and studied. Herein, we report a series of polymers (P1–P3) based on three novel IQD-derived electron-acceptors 5a–c, which were synthesized via aldol condensation reactions between IQD and the dialdehyde of thieno[3,2-b]thiophene (TT), 2,2′-bithiophene (BT), and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT), respectively. P1-based field-effect transistors showed ambipolar charge transport behavior with the electron/hole mobilities (μ_e/μ_h) of 0.04/0.35 cm² V⁻¹ s⁻¹. However, P2- and P3-based ones showed p-type behaviors with high μ_h values of 1.08 and 0.75 cm² V⁻¹ s⁻¹, respectively, which are among the highest in the IQD-based polymers reported so far. Thin film microstructural analyses demonstrated that the more extended π-conjugation and less backbone rigidity of bridging units, and better long-range order in thin films are responsible for the high μ_h of P2 and P3. Our work highlights that IQD is a promising building block for achieving high-performance semiconducting materials and its inner bridging units also have an important influence on the charge transport properties of polymer derivatives.