Professor Wu Peiyi of Donghua University "AFM": Room temperature self-polymerizing ionic gel coating based on α-lipoic acid, used for stretchable and repairable electronic products

[Background introduction]

The goal of stretchable electronics is to accelerate the expansion of the Internet of Things by establishing reliable electrical conductive sub-circuits and components to adapt to a large number of deformed scenes, including sensors, displays, actuators, energy storage devices, and flexible robots.

However, coating stretchable conductors on various substrates has proven to be a very challenging task, and requires comprehensive consideration of the transparency, adhesion, mechanical compliance, shape adaptability and processing properties of the coating.

【Introduction to Achievements】

Recently, East China University professor Wupei Yi , professor Sun Sheng Tong jointly reported only one kind prepared by the concentration of induced spontaneous ion ring-opening polymerization of a natural small molecule gel coat lipoic acid α- (the TA) .

[Highlights of this article]

(1) The ionic liquid prevents the depolymerization of polyTA by forming COOH···O=S hydrogen bonds, thereby forming a super-stretched ionic gel with widely adjustable mechanical and electrical conductivity, self-healing properties, and tissue-like strain adaptability .

(2) Ion gel coatings have universal adhesion and adjustable rheology, and can be directly coated on various substrates with any shape (including porous materials, three-dimensional printing frames and elastic threads) to make them have Ionic conductivity.

(3) The ionic gel coating has high sensitivity and high durability similar to the skin, indicating the great potential of the ionic gel coating in the emerging soft and scalable electronic products.

【Graphic Analysis】

Point 1 Design and Preparation of PolyTA Ion Gel Coating

As shown in Figure 1a, the author found for the first time that TA was dissolved in a relatively high concentration of ethanol.

Figure 1a) Schematic diagram of ring-opening polymerization (ROP) induced by the concentration of TA in ethanol at room temperature.

Point 2 The stabilization mechanism and internal interaction of PolyTA ionic gel

In order to verify the existence of hydrogen bonds in the polyTA ion gel (Figure 2a), the author compared the different components with ATR-FTIR and ¹ H-NMR spectra.

Figure 2a) Schematic diagram of COOH···[ES]H bond (atomic tag is used for IR and NMR analysis); b, c) ion gel (TA: IL=5:1), [EMI][ES] and Comparison of ATR-FTIR and ¹ H NMR spectra of poly TA ; d) The interaction energy of four pairs of components was calculated by molecular dynamics simulation; e) Storage and loss of poly TA ion gel in a heating-cooling cycle Modulus changes with temperature.

Point 3 Strain adaptation and healing properties of PolyTA ionic gel

As a coating for stretchable conductors, polyTA ion gel coatings have very important tensile properties.

Figure 3a) Tensile stress-strain curves of ionic gels with different TA:IL molar ratios.

Point 4  Strain adaptation and healing properties of PolyTA ionic gel

，(HPC)，。HPC，。HPC0.

4 a）HPC（TA:IL=5:1）-。0.

5 PolyTA

polyTA。5aTA0%200%，，。(5b)，polyTA。，，，(5c)。，，/(5d)。polyTA，200%2500，(5e)，polyTA。，polyTA3D(5 g-5 h)。（5i）。，（5 j）。，polyTA，。

5 a）TA。b）。c）。d），。e）200%，2500。f）。g、h）TPU3DSEM。i）。j）。k）0%140%。l）。

【】

In summary, the author reports a polyTA ion gel coating with a simple preparation method, which can be sprayed or penetrated adaptively to various insulations with arbitrary shapes (planar, non-planar, porous, 3D printing, textiles, etc.

Original link:

https://onlinelibrary.
wiley.
com/doi/10.
1002/adfm.
201909042