Fabrication And Property Of Conjugated Polymer Nanoparticles Doping Silver/resin Electrically Conductive Composites

Resin-based electrically conductive composites were a kind of great potential packaging materials.But the electrical properties and mechanical properties of electrically conductive composites were not very good,which would hinder its commercialization.Therefore,it was urgent to explore a simple and effective method that could simultaneously improve the electrical properties and mechanical properties of electrically conductive composites.This thesis proposed a method of using conjugated polymer nanoparticles to dope electrically conductive composites to improve the overall performance.First,oxidative polymerization and dispersion polymerization methods were used to prepare highly conductive,highly dispersible conjugated polymer nanoparticles.A new phenomenon was discovered that trace doping of conjugated polym ers can increase the conductivity of electrically conductive composites by dozens of times.At the same time,it was found that the conjugated polymer reinforced flexible conductive composite material had better mechanical stability and longer service life.This method solved the technical contradiction that it was difficult to improve the electrical properties and mechanical properties of electrically conductive composites simultaneously.This thesis revealed the mechanism of simultaneous improvement of electrical properties and mechanical properties when electrically conductive composites were doped with conjugated polymers,which was caused by the electrostatic force interaction between the conjugated polymer nanoparticles and the silver flakes that induced changes in the microstructure.conjugated-polymer-enhanced electrically conductive composites showed excellent application prospect in the fields of electrically conductive adhesives,printed flexible circuits,flexible sensors,and printed flexible RFID.First,the synthesis processes of conjugated polymer materials for doping and various conductive silver fillers were explored.Protonic acid doping highly conductive conjugated polymer materials were prepared by in-situ oxidative polymerization method.Simultaneously,surfactants such as PVP and SDS were used to improve the dispersibility of conjugated polymer nanoparticles.In this thesis,polyaniline（PANI）nanobranches and polypyrrole（PPy）nanospheres were prepared with the smallest diameter of 60.6nm±8.7nm and 86.8nm±11.8nm respectively.And it was found that PPy nanospheres with the best monodispersity could be prepared when the water-alcohol ratio is 20%:80%.It was difficult to print the conductive paste after doping undispersed conjugated polymer nanoparticles.A variety of conductive fillers were prepared using polyol methods,ball milling methods,etc.,including silver nanowires,silver nanoparticles,silver dendrites,and micron silver flakes.It was found that the morphology of the conductive fillers would affect the electrical properties of the electrically conductive composites.Silver-dendrites-filled electrically conductive composites and micron-silver-flakes-filled electrically conductive composites showed the best electrical properties.And the micron-silver-flakes-filled electrically conductive composites showed better printing performance.Next,the electrical properties,mechanical properties,printing properties and service reliability of conjugated polymers（PANI,PPy,PEDOT:PSS）doping electrically conductive composites used as electrically conductive adhesives were studied.It was found that the addition of the above three conjugated polymer materials could significantly improve the electrical performance of the electrically conductive adhesives.This method could improve the electrical performance of electrically conductive adhesives by more than 13.0 times.The minimum resistivity of the electrically conductive adhesives was 9.3×10^-5Ω·cm.And it was proved that the method was also suitable various epoxy-based electrically conductive adhesives.It was shown that the PPy and PANI doping electrically conductive adhesives had the same shear strength as the original shear strength,and the shear strength could reach11.1MPa±0.4MPa.During thermal aging and high temperature and high humidity test,the resistance of PPy and PANI doping electrically conductive adhesives decreased first and then stabilized,without reliability problems.Mechanism of conjugated polymers could improve electrical properties of conductive composites was further elaborated through microstructure characterization.The highly conductive conjugated polymer nanoparticles increased the electron tunneling area and improved the electrical properties of the electrically conductive composites.Subsequently,the electrical properties,mechanical properties and service reliability of flexible electrically conductive composites doped with conjugated polymers were studied.PANIs were used to dope a variety of flexible resin-based（TPU,PVB,Ecoflex）electrically conductive composites.It was found that only 0.5wt%PANI doping could reduce the resistivity of 60wt%silver-filled PVB-based electrically conductive adhesives from 1253.1×10^-5Ω·cm to 37.1×10^-5Ω·cm,and the electrical performance was improved by 33.7 times at most.In the experiment,the minimum resistivity is 7.7×10^-5Ω·cm.Bending test,twisting test and tensile test have been done for the requirements of resistance stability during deformation in the application of electrically conductive composites.The experimental results show ed that PANI enhanced flexible conductive composites exhibit better resistance stability and service life.For example,in the bending experiment,the relative resistance fluctuation could be reduced from 92%to 2.3%,and the bending life significantly prolonged to more than 2500 times.Extension life increased from 700 times to more than 3500 times.It was found that heating would optimize the electrical properties of electrically conductive composites.Through microstructure analysis,it was found that the distribution of silver flakes in the flexible conductive composite material changed after doping PANI nanoparticles.It was believed that structural changes disrupted the distribution of resin between the silver flakes and improved their electrical properties.Silver flakes distributed in the interlaced state reduced the Young’s modulus of the electrically conductive composites,which improved its electrical properties,mechanical properties at the same time.Finally,a variety of conjugated polymer enhanced electrically conductive composites realized the applications in the field of printed flexible circuits,flexible sensors,and printed flexible RFID.The flexible printed circuit could still work stably during the bending and deformation process,which proved that the conjugated polymer enhanced electrically conductive composites showed excellent mechanical stability.Flexible sensor enabled real-time monitoring of various human motions.Printed flexible RFID antennas showed more stable communication performance after mechanical deformation.At the same time,conjugated polymers enhanced electrically conductive composites were compatible with a variety of unwettable substrates and SMT printing process.It was considered that the conjugated polymers enhanced electrically conductive composites had broad application prospects in the field of flexible electronics.