We present a series of newly developed donor‐acceptor (D‐A) polymers designed specifically for organic electrochemical transistors (OECTs) synthesized by a straightforward route. All polymers exhibited accumulation mode behavior in OECT devices, and tuning of the donor comonomer resulted in a three‐order‐of‐magnitude increase in transconductance. The best polymer gFBT‐g2T, exhibited normalized peak transconductance (gm,norm) of 298±10.4 S cm‐1 with a corresponding product of charge‐carrier mobility and volumetric capacitance, μC*, of 847 F V‐1 cm‐1 s‐1 and a μ of 5.76 cm2 V‐1 s‐1, amongst the highest reported to date. Furthermore, gFBT‐g2T exhibited exceptional temperature stability, maintaining the outstanding electrochemical performance even after undergoing a standard (autoclave) high pressure steam sterilization procedure. Steam treatment was also found to promote film porosity, with the formation of circular 200 – 400 nm voids. These results demonstrate the potential of gFBT‐g2T in p‐type accumulation mode OECTs, and pave the way for the use in implantable bioelectronics for medical applications.