Synthesis, Characterization, and Field-Effect Transistor Properties of Naphthalene Diimide-Based Conjugated Polymers with Fluorine-Containing Branched Side Chains

The side chains of polymeric semiconductor materials not only provide solubility to the conjugated backbones but also affect the stacking state of the polymer segments, thus affecting the carrier mobilities. In this work, three naphthalene diimide (NDI)-based conjugated polymers with novel fluorine-containing branched side chains were synthesized and characterized for their performances in solution-processed organic field-effect transistors (OFETs). For the side chain, n-heptafluorobutanyl (−C3F7) was introduced as the terminal group and the alkyl chain branching point was located at three carbon atoms away from the conjugated main chains. The GIWAXS analysis revealed that stacking occurred only in the random lamellar direction and not in the π–π direction for the three polymers. All polymers were characterized by typical n-type dominant semiconductor transmission with the highest electron mobility (μe) of up to 1.83 × 10–2 cm2 V–1 s–1 with Ion/Ioff = 105 and exhibited good thermal stability and environmental stability.