Functional Zwitterionic Polyurethanes as Gate Dielectrics for Organic Field-Effect Transistors

The development of polymeric dielectrics with a high dielectric constant is of great significance for flexible low-voltage organic field-effect transistors (OFETs). Herein, functional polyurethanes (PUs) with nitro and sulfobetaine zwitterionic groups are synthesized, and their electrical properties, mechanical properties, and the performances of OFET devices using these zwitterionic PUs as gate dielectrics are studied. Compared with sulfobetaine zwitterion-containing PUs, nitro-containing PUs (NO₂-PUs) show higher dielectric constant up to 6.5. Both zwitterionic PUs enhance the OFET performances, while the effect of NO₂-PU is more significant. Devices using NO₂-PU-15 that contains 15 moL% nitro groups as the dielectric layer show the best performance and a threshold voltage (V_th) of as low as −0.02 V together with two orders’ increase of the mobility is observed, compared with the devices using PU without nitro groups. This study provides a new method to improve the dielectric constant of polymeric dielectrics, which is valuable for flexible/stretchable and wearable electronic devices.