Preparation And Properties Of The Highly Elastic And Resistance Stable PEDOT:PSS Fibers

Highly conductive and stretchable fibers are crucial components of stretchable electronics systems.However,the fabrication methods involved are usually complicated,and it is challenging to achieve high stretchability while maintain their conductivity.These problems greatly limited their development in the area of stretchable electronic devices.In order to solve these problems,the PEDOT:PSS fibers and PEDOT:PSS/TPE fibers via wet-spinning followed by hot-drawing and coaxial wet-spinning assembly approach were fabricated.Combined structure design of materials,adjustment the parameters when spinning and post-treatment,the highly elastic and resistance stable PEDOT:PSS fibers were fabricated successfully.Also,the mechanism of the improvement of the electrical conductivity and stretchability of the fibers is revealed.The combination of scalable,green coaxial wet-spinning technology and excellent electrical a stretchable performance of the fiber paves the way to stretchable electronics.Firstly,we fabricated high-performance PEDOT:PSS conjugated polymer microfibers.The fabrication technique lies in a two-step method(wet-spinning followed by immediate hotdrawing)that greatly promotes molecular alignment.The optimum wet-spinning parameters were obtained through the control of parameters during the spinning process,in which the spinning rate was 6 ?L/min and the spinning needle was 27 G.In addition,The microstructure of the fiber improved by the non-ionic surfactant Triton X-100(The following is abbreviated as TX)and polymer-based surfactant Polyethylene-block-poly(ethylene glycol)(abbreviated as PBP)doped and EG vapor post-treatment to further increase the electrical conductivity and mechanical properties of the PEDOT:PSS fiber.Due to the combined effects of the vertical hotdrawing process,doping/de-doping the microfibers with two different surfactants and Ethylene glycol(EG)vapor annealing,a highly electrical conductivity of 1812±90 S/cm was achieved.Moreover,a 4.7-fold improvement over the best values for as-spun PEDOT:PSS fibers(314±13 S/cm)and a 2.5-fold improvement over the best values for conductive polymer fibers treated by Triton X-100 doping(550±10 S/cm).The microstructure analysis shows that the increase of the fiber conductivity is mainly due to the conformational changes of the PEDOT chains from benzoid to quinoid structure increased interchain interaction,thereby enhancing the structural change in PEDOT:PSS from a coil to a linear or an extended-coil conformation and the conductivity of the surfactant or EG vapor annealing-treated PEDOT:PSS fibers.However,the electro-mechanical properties test showed that the resistance increased with the strain increasd and all fibers have a small elongation before failure(< 36%).When the fraction of the Polyethylene-block-poly(ethylene glycol)was 0.7,the fibers have a maximum strain up to 36% before failure,and the maximum strain before failure is 1.9 times that of the as-spun fiber.To further improve the stretchability of the fiber and obtain the resistance stable fiber,a coaxial wet-spinning assembly strategy followed by pre-strain is proposed to readily prepare thermoplastic elastomer(Polystyrene-block-polyisoprene-block-polystyrene)-wrapped PEDOT:PSS conductive polymer core-sheath fibers that are applied directly as contactable and interweaving electrodes without the risk of short circuit.When the pre-strain was greater than 700%,the core layers exhibited a "wavy +buckling + fold" hierarchically structure,greatly improving the stretchability of the core-sheath fibers.When the fraction of polyethylenepolyethylene glycol block copolymer is 0.7 in the core layers and the prestrain is 700% and 900%,the resistance change of the fibers were less than 5% for a 700% stretch.