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Mass production of ultrafine polyaniline fibers for tactile organic electrochemical transistors

Time:2022-04-25 Hits:

The development of Conducting Polymer Fibers (CPFs) is critical to the development of Conducting Polymer Fibers from advanced fiber devices to cutting-edge fabric electronics. The use of continuously conducting polymer fibers requires a small diameter to maximize their electrically active surface, microstructure orientation, and mechanical strength. However, the commonly used wet spinning technology is difficult to achieve this goal.
Recently, the Hong Kong Polytechnic University (PolyU) team proposed a good solvent exchange strategy to fabricate ultra-fine polyaniline (PAni) fibers (UFPFs) on a large scale using an improved wet spinning technique. The slow diffusion between good solvents obviously reduces the viscosity of the fibrils and makes the fibrils have excellent tensile ratio. The diameter of UFPFs obtained is less than 5μm. In addition, the ultra-fine morphology and highly improved electroactive surface promote the excellent electrochemical activity and mechanical properties of the polymer. The related work is known as Scalable production of ultrafine polyaniline fibres for tactile organic synthesis "Commentary is published in the latest issue of Nature Communications.

Preparation and characterization of UFPFs
In an improved one-step wet spinning process, UFPFs were mass-produced using a good solvent as a coagulating bath. The researchers observed that the diameter of the gel fibers decreased dramatically when stretched in the bath. Microfibers have smooth surface, highly crystallized microstructure and uniform electrical properties. In addition, the excellent draw ratio enables UFPFs to produce efficiencies in excess of 40 m/min. For example, it takes only 2h to prepare a 5.4km long UFPF.

We further investigated the effect of the tapering behavior of the gel fibrils on the polyaniline chain by using a good solvent as coagulating bath, and speculated that the tapering phenomenon may be caused by two factors: diffusion difference and interfacial pressure. UFPFs has excellent mechanical properties. Different from traditional polymer fibers, the strain-stress curve of UFPFs shows brittle fracture behavior, and the tensile strain is 3.67%±0.64%. UFPFs has a modulus of 29.89±5.6 GPa and a strength of 1080±71 MPa.

Energy and charge storage capacity
The ultra-fine morphology optimizes the electrically active surface, enabling UFPFs to exhibit superior energy and charge storage capabilities. It was found that the potential and capacitance did not decrease significantly in 120 charge-discharge cycles, indicating that UFPFs had excellent electrochemical stability.

Structure and performance of all solid state OECT
Thanks to the excellent energy and charge storage performance of UFPFs, researchers have demonstrated a high-performance all-solid-state photodiode OECT. Due to the remarkable flexibility and transparency of PVA and PU, all-solid OECT is very soft, with a transmittance of more than 80% in the visible region and a thickness of less than 300μm.

(Source: Frontiers in Polymer Science)