Abstract
Stretchable conducting materials are appealing for the design of unobtrusive wearable electronic devices. Conjugated polymers with oligoethylene glycol side chains are excellent candidate materials owing to their low elastic modulus and good compatibility with polar stretchable polymers. Here, electrically conducting elastomeric blend fibers with high stretchability, wet spun from a blend of a doped polar polythiophene with tetraethylene glycol side chains and a polyurethane are reported. The wet-spinning process is versatile, reproducible, scalable, and produces continuous filaments with a diameter ranging from 30 to 70µm. The fibers are stretchable up to 480% even after chemical doping with iron(III) p-toluenesulfonate hexahydrate and exhibit an electrical conductivity of up to 7.4 S cm-1 , which represents a record combination of properties for conjugated polymer-based fibers. The fibers remain conductive during elongation until fiber fracture and display excellent long-term stability at ambient conditions. Cyclic stretching up to 50% strain for at least 400 strain cycles reveals that the doped fibers exhibit high cyclic stability and retain their electrical conductivity. Finally, a directional strain sensing device, which makes use of the linear increase in resistance of the fibers up to 120% strain is demonstrated.
Highlights
The fibers gradually solidify in the coagulation bath, before being collected and wound onto a bobbin. Both p(g42T-T) and the here used polycarbonate-based PU could be readily dissolved in dimethyl formamide (DMF) even at the required high concentrations of 50–70 g L−1
We have previously argued that doping with dodecylbenzenesulfonic acid (DBSA) or ethylbenzene sulfonic acid (EBSA) entails an acid mediated oxidation of the polymer through oxygen.[77]
We have presented wet spun blend fibers of p(g42T-T) and PU which display both mechanical and electrical stretchability of up to 480% after doping with iron(III) p-toluenesulfonate hexahydrate (Fe(Tos)3·6H2O)
Summary
During wet spinning of polymer fibers, the constituent polymers are first dissolved and extruded into a coagulation bath. We found that our first batches of PU fibers, spun from a polymer solution of 50 g L−1 into a coagulation bath of 1:3 IPA:water (extrusion rate 3 mL h−1, 27 G needle) had a flattened cross section indicating insufficient. An increased length of the spinline path inside the coagulation bath improved the removal of DMF prior to collection, preventing the fiber from flattening on the take-up roller This process resulted in circular/ semi-circular fibers, denoted Fmidi, with a diameter of ≈60 μm and an average cross-sectional area of ≈2870 μm (Figure 2d, Table 1). By further increasing the polymer solution concentration to 70 g L−1, we could prepare thicker fibers, referred to as Fthick, with a diameter of ≈70 μm and a cross-sectional area of ≈3810 μm (Figure 2c, Table 1; see Figure S2, Supporting Information for an overview of the employed processing parameters). We chose to dope fibers with Fe(Tos)3·6H2O in AcN for 24 h for all further experiments
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
