Synthesis and Electrical Characterization of Poly[(linoleic acid) ‐g‐ (styrene) ‐g‐ (ε‐caprolactone)] Graft Copolymers as Gate Insulator for OFET Devices

Abstract This study reports a one‐pot process used to synthesize poly[(linoleic acid)‐ g ‐(styrene)‐ g ‐( ε ‐caprolactone)] (PLina‐ g ‐PSt‐ g ‐PCL) graft copolymers. The process was carried out by combining the atom transfer radical polymerization of styrene with the ring‐opening polymerization of ε ‐caprolactone from polymeric linoleic acid having hydroxyl groups and bromine groups in the main chain. The characterization of the products was achieved using proton nuclear magnetic resonance, size‐exclusion chromatography, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry techniques. Subsequently, an organic field effect transistor (OFET) was fabricated with PLina‐ g ‐PSt‐ g ‐PCL graft copolymers as the insulator layer. Poly(3‐hexylthiophene) (P3HT) was used as the active layer and prepatterned OFET substrates were used as the welding/discharge electrodes. To measure capacitance, an ITO/P3HT/PLina‐ g ‐PSt‐ g ‐PCL/Al structure was prepared using the same method. To obtain output and transfer current–voltage characteristics, electrical characterizations of OFET devices were conducted in darkness and an atmosphere of air. From a capacitance–frequency plot, the key characteristics of the devices, including the threshold voltage ( V Th ), field effect mobility, and current on/off ratio ( I on/off ), were derived. The fundamental electrical parameters in the fabricated OFET devices based on styrene concentration were thoroughly examined. It was observed that the produced PLina‐ g ‐PSt‐ g ‐PCL OFETs display positive device characteristics such as low V Th , exceptional mobility, and I on/off values. © 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.