The highest performing polymer batch was P3MEEET-3 when operated in KTFSI (µC* of 332 F cm -1 V -1 s -1 ), which showed optimized µ (2.14 cm 2 V -1 s -1 ); a remarkable performance for this class of OMIECs. These results underscore the added complexity of determining molecular design guidelines for mixed conductors which undergo volumetric rather than interfacial electrochemical or electrostatic operation (i.e. EGOFETs or OFETs). The relationship between molecular weight and performance is therefore anticipated to be material dependent, as materials such as P3MEEET display detrimental swelling at higher molecular weights (thus amplifying electrolyte dependence), while other materials which lack side chains such as BBL show minimal passive swelling. This work provides a molecular design strategy to optimize OECT performance for glycolated polythiophenes and offers insight into how such material properties can be investigated and leveraged for other classes of mixed conductors.