Abstract:

Objective Intelligent textiles with excellent serviceability and electrical performance require the use of high-performance conductive fibers. Wet-spun conductive fibers have great potential in various smart and functional yarns and fabrics. The doping of conductive fillers into fibers is an efficient way to improve fiber conductivity. However, the effect of conductive fillers dispersed into the coagulation bath on the electrical properties of wet-spun fibers was not sufficiently investigated. This research aims to study the effect of doping method and doping ratio of conductive fillers on the electrical properties of poly (3,4-ethylene supported dioxythiophene):polystyrene sulfonic acid(PEDOT:PSS)-based fibers.

Method Graphene and silver nanowires (Ag NWs) were used as conductive fillers, PEDOT:PSS was used as the matrix, deionized water was used as the solvent, isopropanol and dimethyl sulfoxide were used as coagulation bath to fabricate wet-spun PEDOT:PSS based composite fibers. Conductive fillers were directly mixed into the spinning solution or only dispersed into the coagulation bath. In addition, polyurethane (PU) encapsulated composite fiber was fabricated by the immersion method.

Results The wet-spun composite fibers showed uniform diameter. Based on the bidirectional diffusion of spinning liquid and coagulators, the graphene and Ag NWs dispersed in the coagulation bath were closely adsorbed onto the surface of the PEDOT:PSS fiber. The PEDOT:PSS fiber doped with Ag NWs into spinning solution (sample 4) demonstrated the highest electrical conductivity (577.98±157.33) S/cm, and PEDOT:PSS-based composite fiber (sample 7) fabricated by graphene and Ag NWs dispersed into the coagulation bath showed the second-highest conductivity (421.19±75.14) S/cm. Considering the cost in real production, composite fibers (sample 7) fabricated in the coagulation bath with conductive fillers were considered more feasible. The strain and stress of the composite fiber were 1.23% and 37 MPa, respectively. The resistance of the composite fiber showed gradual increasing during the tensile loading process. When the strain reaches 0.75%, the gauge factor (GF) of composite fiber was 0.18 and was increased to 3.12 until it breaks at 1.23%. The static contact angle of composite fiber was 62.9°. The electric conductivity of polyurethane (PU) encapsulated composite fibers illustrated a decrease by 10.7% compared with that of composite fiber, but demonstrated ability to withstand cyclic three-point bending 6 000 times after which the resistance change of the fiber was below 0.12%. After water washing, the resistance of the PU encapsulated composite fiber was increased. After three times of water washing (about 30 min), the conductivity of encapsulated fiber stabilizes and remained at 260 S/cm.

Conclusion In this work, PEDOT:PSS based composite fiber with high conductivity and good stability are prepared by the wet spinning method. By adjusting the doping ratio and methods of graphene and silver nanowires into PEDOT:PSS, the conductivity of composite fibers is improved. Dispersing conductive fillers into the coagulation bath is found to be more feasible to fabricate high-performance conductive composite fibers. The resulting composite fibers show promise for small strain sensing and the surface of composite fiber is hydrophilic. The PU-encapsulated composite fibers exhibit good bending resistance as well as the water washing resistance. After three times of water washing, the electrical performance of PU-encapsulated composite fiber becomes stable. The proposed methods provide a new approach for wet-spun conductive composite fibers to achieve high electric conductivity and good stability simultaneously.

Key words: conductive fiber, poly(3,4-ethylene supported dioxythiophene): polystyrene sulfonic acid, graphene, silver nanowire, wet spinning, conductive property