Study On Preparation And Properties Of PEDOT:PSS/PVA Conductive Fiber

Poly?3,4-ethylenedioxythiophene?:poly?styrene sulfonate??PEDOT:PSS?is a novel conducting polymer which is regarded as the next-generation candidate for conductive materials due to its high conductivity,good environmental stability,and outstanding processability from aqueous solution.PEDOT:PSS conductive fiber can be prepared by wet-spinning technique.PEDOT:PSS conductive fiber can achieve high conductivity comparable to metals,however,preparing single-component PEDOT:PSS conductive fiber is complicated and costly.Furthermore,single-component PEDOT:PSS conductive fiber can not meet the weaving requirement of further application due to high brittleness and high modulus.Therefore,exploring a kind of composite conductive fiber based on PEDOT:PSS to overcome those defects mentioned above is important for smart fiber development from both fundamental and industrial areas.Poly?vinyl alcohol??PVA?is a water-soluble polymer,which has excellent film forming ability,adhesive property,degradability,as well as good skin adaptability and biocompatibility.In this work,PVA was chosen as fiber-forming substrate blended with PEDOT:PSS to prepare PEDOT:PSS/PVA composite conductive fiber via wet-spinning technique.After that,fiber structures and mechanical properties were optimized and improved by adjusting technological conditions during wet-spinning process.Finally,fiber conductivity was enhanced by three different doping methods:dimethyl sulfoxide?DMSO?additive doping method,ethylene glycol?EG?vapor annealing treatment,and ultraviolet?UV?irradiation treatment in vacuum chamber.Enhancement in fiber conductivity extends application prospects of PEDOT:PSS/PVA composite fibers in wearable smart textiles.In this work,we firstly investigated the effects of PEDOT:PSS content on structure and properties of PEDOT:PSS/PVA composite conductive fiber.Fiber conductivity increased exponentially with increasing PEDOT:PSS content.Tensile strength of composite fiber increased while elongation at break decreased with increasing PEDOT:PSS content due to the introduction of PEDOT:PSS increasing the molecular chain rigidity of PEDOT:PSS/PVA composite conductive fiber.Increasing in PEDOT:PSS content facilitated cross-section formation from non-circular shape to regular circular shape.Increase in PEDOT:PSS content reduced the mass transfer rate difference between the solvent and non-solvent,and thus balanced the double diffusion rate between spinning formulation and coagulation bath.PEDOT:PSS/PVA composite conductive fiber achieved the conductivity of 11.25 S·cm^-1,tensile strength of 124.15 MPa,and elongation at break of 24.1%.Secondly,we successfully optimized fiber structures and improved tensile properties of PEDOT:PSS/PVA composite fibers by adjusting several processing conditions including components of coagulation bath,draw ratio,rinsing times,and heat-setting temperature during wet-spinning process.Change in components of coagulation bath balanced the double diffusion rate between solvent in spinning formulation and non-solvent in coagulation bath,leading to slower formation process,and therefore facilitated to form regular circular cross-section of fiber.Drawing oriented molecular chains and regulated microfibrils along fiber axial direction,thus reducing structural defects inside fibers such as micropores and microvoids.Rinsing removed residual non-solvent and impurities in fiber,leading to purification of fiber component and therefore alleviated fiber property deterioration due to residual impurities.Heat setting treatment densified fiber structure.With the following processing condition:methanol/isopropyl alcohol volume ratio of 1/1,drawing ratio of 5 times,rising time of twice,heat-setting temperature of 150?,PEDOT:PSS/PVA composite fiber achieved the tensile strength of 230.04 MPa,elongation at break of 30.67%.Meanwhile,fiber achieved the conductivity of 14.07 S·cm^-1,as well as regular circular shape and dense structure.Ultraviolet light was employed to irradiate PEDOT:PSS/PVA composite fibers under vacuum to improve electrical properties of fibers.PSS chains broke up and cross-linked under UV-light irradiation,which facilitated multiple conductive paths among PEDOT grains,thus enhancing electrical conductivity of composite fibers.Under UV-light irradiation,75%polarons paired to bi-polarons which had higher delocalization degree,leading to higher charge carrier mobility,and therefore enhancing electrical conductivity of composite fiber.PEDOT:PSS/PVA composite fiber achieved conductivity of 52.34 S·cm^-1 under 10 h UV light irradiation.UV-light irradiation broken partial PVA chains therefore lowered tensile strength of composite fibers.Under 10 h UV-light irradiation,composite fiber achieved tensile strength of191.93 MPa,and elongation at break of 21.95%.EG vapor annealing treatment was employed on PEDOT:PSS/PVA composite conductive fiber to improve electrical properties of fibers.EG vapor annealing induced significant phase separation between PEDOT and PSS.Partial PSS chains enriched onto surface of composite fibers,reducing thickness of PSS insulating layers among conductive PEDOT grains as well as lowering migration barrier of carrier transportation,which was beneficial to form tunneling current between adjacent PEDOT grains,thus enhancing electrical conductivity of PEDOT:PSS/PVA conductive fibers.As EG vapor annealing time increased,surface of composite fiber became smoother.Under 30 min of EG vapor annealing treatment,composite fibers achieved Young's modulus of 17.63 GPa,tensile strength of 198.37 MPa,and elongation at break of 22.81%.Electrical properties of PEDOT:PSS/PVA composite conductive fiber was improved by DMSO additive doping method.Molecular conformation of PEDOT transferred from benzoid structure to quinoid structure after DMSO doping.Quinoid structure was more favorable for charge carrier transportation,leading to reduction in carrier transportation barrier,and therefore enhanced fiber conductivity.As DMSO doping content increased,surface roughness of composite fiber increased,as well as tensile strength,while elongation at break decreased.With a DMSO doping content of 8 wt%,PEDOT:PSS/PVA composite conductive fiber achieved the conductivity of 51.7 S·cm^-1,Young's modulus of 19.85 GPa,tensile strength of 275.43 MPa,and elongation at break of 16.95%.