Interfacial Polymerization Of Polypyrrole And Functional Applications In Wearable Materials

Compared with traditional rigid materials,flexible wearable electronic materials have already attracted attention because of the advantages of deformability,good fitting with flexible objects and curved surfaces.Among them,flexible wearable pressure sensing system which are closely related with human daily activities mainly includes functional modules such as sensing,energy storage,and circuits materials.And realization of the flexible preparation of the above-mentioned materials is conducive to promoting the preparation of a fully flexible system and realizing real flexible wearable.Polypyrrole(PPy)as a conductive polymer takes the advantages of low cost and simple preparation process,and has a wide range of applications in the field of functional materials.This paper uses PPy interface polymerization to strengthen its interaction with flexible substrates,and conducts research on the structural design and performance improvement of piezoresistive fibers,flexible conductors and stretchable energy storage device materials with high stable sensing performance,promoting the functional application of PPy in wearable materials.Aiming at the problem that it is difficult to construct isotropic distributed wrinkles on the surface of fibrous flexible pressure-sensitive sensing materials,PPy@TPU fiber with isotropic distributed micro-wrinkles structure on the surface was successfully prepared by using the modulus mismatch between the PPy conductive layer and the polyurethane(TPU)fiber during the swelling,in-situ polymerization and shrinking process.This study found that due to the existence of the isotropic pleated structure,the overlap unit between PPy@TPU fibers maintains point-to-point contact change under pressure,and there has a better interface bond between the PPy wrinkles on the fiber surface and the TPU fiber.The sensing fiber not only shows high sensitivity(0.041 k Pa^-1),fast response(response time less than 47 ms),but also has excellent sensing stability(more than 3000 cycles).The PPy@TPU fiber has good response performance to stresses of different sizes and frequencies,and can be used to monitor human activities such as pulse,limb pressure and joint movement.Aiming at the problem of interface instability of the flexible conductor line,a flexible conductor based on polypyrrole@liquid metal(PPy@LM)core-shell particles was successfully prepared on polyurethane(TPU)substrate by ultrasonic dispersion and chemical oxidation polymerization.Studies have shown that when the ultrasound time is 20 min,the LM microdroplets have a uniform particle size distribution with an average particle size of 214 nm.The line resistance per unit length is 15.15 k?/cm after the oxidation reaction for 20 min.While the flexible circuit based on PPy@LM core-shell particles is subjected to mechanical force,the LM wrapped inside will flow out to reduce the circuit resistance to 280?/cm because liquid metal(LM)has high conductivity.Utilizing good wettability between pyrrole and TPU,the PPy prepared after interfacial polymerization can strengthen the interface between the circuit and the substrate.It exhibits excellent working stability,the resistance is reduced by 6.3%after more than 5000 times cycle numbers(the bending angle is 180°),which can be used as a conductor material in a wearable pressure sensing system.Utilizing the excellent pseudocapacitance properties of PPy,the intrinsic stretchable PPy@Ni/LM supercapacitor electrode material was successfully prepared by electrochemically depositing PPy on the surface of the stretchable current collector(Ni/LM and VHBTM tape).When the electrodeposition time is 20 min,the electrode material has good electrochemical performance,with a specific capacity of 162.34 m F/cm²(10 m V/s).After being assembled into a supercapacitor,the specific capacity reaches 28.76 m F/cm²(10 m V/s),and the capacity retention rate is above 80%after 1000 testing cycles.At the same time,the assembled flexible supercapacitor has better stretchability.When the central angle corresponding to the bending deformation is 360°,the specific capacity retention rate is as high as 94.4%.When the tensile strain is less than 20%,the specific capacity retention rate reaches 98.21%.After 100 cycles at50%tensile strain,the specific capacity retention rate is 82.70%.It shows that it can maintain good electrochemical performance under different deformations,and is expected to be used as a stretchable energy storage material in wearable pressure sensing systems.