The development of high-performance n-type semiconducting polymers remains a significant challenge. Reported here is the construction of a coplanar backbone viaintramolecular hydrogen bonds to dramatically enhance the performance of n-type polymeric mixed conductors operating in aqueous electrolyte. Specifically, glycolated naphthalene tetracarboxylicdiimide (gNDI) couples with vinylene and thiophene to give gNDI-Vand gNDI-T, respectively. The hydrogen bonding functionalities are fused to the backbone to ensure a more coplanar backbone and much tighter π–π stacking of gNDI-Vthan gNDI-T, which is evidenced by density functional theory simulations and grazing-incidence wide-angle X-ray scattering. Importantly, these copolymers are fabricated as the active layer of the aqueous-based electrochromic devices and organic electrochemical transistors (OECTs). gNDI-Vexhibits a larger electrochromic contrast (ΔT= 30%) and a higher coloration efficiency (1988 cm2C−1) than gNDI-Towing to its more efficient ionic–electronic coupling. Moreover, gNDI-Vgives the highest electron mobility (0.014 cm2V−1s−1) and μC* (2.31 FV−1cm−1s−1) reported to date for NDI-based copolymers in OECTs, attributed to the improved thin-film crystallinity and molecular packing promoted by hydrogen bonds. Overall, this work marks a remarkable advance in the n-type polymeric mixed conductors and the hydrogen bond functionalization strategy opens up an avenue to access desirable performance metrics for aqueous-based electrochemical devices.