Preparation And Applications Of Ion-doped PEDOT:PSS Fibers By Wet Spinning

Conductive polymers are a class of optoelectronic materials with high ?-? conjugated structure,which have many potential applications in preparing flexible,printable and wearable electronic devices.Poly(3,4-ethylenedioxythiophene)(PEDOT)is one of the most promising conductive polymers with high conductivity at room temperature and can form stable dispersion in water with poly(styrene sulfonate)(PSS).Compared with 2D film,1D fiber material has natural advantages in flexibility,integrability and braidability.Wet spinning is the most important technology for continuous and large-scale preparation of conductive fibers.PEDOT:PSS fiber prepared by wet spinning has attracted widespread attention of researchers.However,the continuous rigid molecular backbone of PEDOT makes it difficult to balance the stretchability and electrical conductivity,which also limits the large-scale application of PEDOT:PSS fiber in the field of wearable electronics.Therefore,the development of a high conductivity PEDOT:PSS fiber with both stretchability and the ability to detect and transmit electrical signals is still a research hotspot in this field.Meanwhile,the surface morphology and structure of conductive fibers have obvious influence on the application of wearable electronics.At the same time,wearable devices will inevitably be affected by some mechanical forces and environmental changes.Therefore,the stability to the external mechanical stimulus and environmental temperature is also an important requirement for them.In this thesis,the preparation of PEDOT:PSS fiber with high elongation and high conductivity by ion doping was approached.In addition,the continuous preparation of high sensitivity PEDOT:PSS fibers with different surface microstructures and PEDOT:PSS fibers with high conductivity and high stability with macroscopic helical morphology were also achieved through ion doping.Firstly,a simple strategy for continuous preparation of PEDOT:PSS fibers by wet spinning with high tensile elongation and electrical conductivity is reported by adding various metal salts to perform electrostatic complexation with PSS in a coagulating bath consisting of water and ethanol,and investigated the potential applications for wearable electronic textiles.It is worth mentioning that the PEDOT:PSS fiber prepared with dropping Li+revealed an over 50%elongation at break.Meanwhile,special anisotropic structures were detected in the fibers doped by lithium ions,and the mechanism of lithium-ion doping improving tensile elongation and conductivity was expounded.In addition,the obtained fibers showed good pressure sensitivity and high energy storage capacity,which provided a new idea for regulating PEDOT:PSS performance at the molecular orientation level.Secondly,inspired by the structure of spider villi,the strategy of ion-induced selfassembly was proposed and realized.The fiber surface with uniform array structure was constructed while the PEDOT:PSS fibers were continuously prepared on a large scale.Copper complexes with a fluff-like shape form spontaneously on the surface of PEDOT fibers without any additional post-treatment or harsh reaction conditions.Due to the fluff-like array structure,the specific surface area of bionic PEDOT:PSS-Cu2+fiber is nearly 5-fold higher than that of the original PEDOT:PSS fiber,which endows it excellent pressure sensitivity,ultra-low detection limit(?82 Pa)and fast response time(47 ms).The potential applications of the fiber in micro airflow detection,real-time information transmission and gravity/pressure sensing were further explored.More importantly,on the basis of studying the influence of multiple metal ion co-doping on the surface structure of PEDOT:PSS fiber,the formation mechanism of the microstructure on the fiber surface was explored,which provided a new idea to regulate the performance of PEDOT:PSS from the level of surface microstructure.Finally,inspired by vine structure of plant,a method to prepare PEDOT:PSS fiber with high mechanical stability and wide temperature stability through controlled spinning process was proposed.By adding phosphoric acid into the coagulation bath,the spinning solution spontaneously formed spiral structure during solidification,and the doping of phosphoric acid to PEDOT was also realized.This process is approached synchronously along with double diffuse in the coagulation bath,without any additional post-treatment.Attributed to the spiral structure of the fiber,the prepared bionic PEDOT:PSS spiral fiber revealed an elongation at break of 300%and excellent electrical conductivity stability in the strain range of 200%.Due to the dual carrier transport channels of PEDOT and phosphoric acid-water,the fiber owns a high conductivity of 498.2 S·cm-1 and excellent resistance to tensile,extrusion and bending.The doping of phosphoric acid also broadens the temperature range at which the PEDOT:PSS fiber can be operated stably.These performance stabilities of fibers also endow the wearable electronics made of fibers good stability.The fibers supercapacitor(FSC)assembled by the fibers showed a specific capacitance of up to 86.2 mF·cm-2,and can still maintain the stability of its capacitance through mechanical action of stretching,bending and twisting.The FSC also showed excellent stability when the ambient temperature changes.Finally,we obtained PEDOT:PSS fiber with good sensing performance by co-doping potassium chloride and phosphoric acid,and realized the selective application of PEDOT:PSS fiber between supercapacitors with high stability and flexible sensors with excellent sensitivity.It greatly widens the applications of PEDOT:PSS fibers and meets the electrode material requirements of a new generation of fiber-based flexible electronic devices.