Lo, Hung-ChiHung-ChiLoHu, Jie-DongJie-DongHuChou, Che-MinChe-MinChouChen, Chun-YuChun-YuChenLin, Jhih-MinJhih-MinLinChen, Chin-WenChin-WenChenCHIEN LUNG WANGChuang, Wei-TsungWei-TsungChuangWu, Kuan-YiKuan-YiWu2025-08-222025-08-222025-07https://scholars.lib.ntu.edu.tw/handle/123456789/731570Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fibers with excellent electrical conductivity and stretchability are crucial for advancing wearable fiber-based electronics. However, the tensile strength and stretchability remain constrained by the hierarchical structure of PEDOT:PSS. Notably, the role of PSS molecular weight (Mw) in shaping the processability and mechanical performance of PEDOT:PSS fibers has not been explored yet. Herein, we examine the impact of PSS Mw on the process-structure–property relationship of PEDOT:PSS fibers. PSS with the higher Mw of 500 and 1000 kg mol−1 were used to produce PEDOT:PSS500 and PEDOT:PSS1000, compared to Clevios PH1000. Structural analysis shows that all the PEDOT:PSS solutions have a comparable PEDOT-to-PSS weight ratio. Increasing the Mw of PSS enhances solution viscosity, thereby improving fiber spinnability. The tensile strength is also improved in high Mw PEDOT:PSS fibers since the elongation at break (Ebreak) increases from 11.8 % in PH1000 to 39.3 % in PEDOT:PSS1000 at RH = 60 %. After the DMSO/glycerol-immersed treatment, the PEDOT:PSS1000 fibers deliver a high conductivity of 110 S·cm−1. Besides, the PEDOT:PSS1000 fiber can exhibit high Ebreak = 48.8 % at RH = 80 % and still perform Ebreak = 13.7 % even at low RH = 20 %. These findings highlight the potential of tailoring PSS Mw to enhance the performance of PEDOT:PSS fibers for wearable electronics.enFiber spinningPEDOT:PSS fiberStretchabilityWearable electronicsjournal article10.1016/j.eurpolymj.2025.114085