| The flexible conductive adhesives are composed of conductive fillers and flexible matrix,which can be a promising candidate in the fields of wearable devices, flexible displays,flexible sensors and such novel flexible electronics. The volume resistivity of theseconductive adhesives can be maintained during bending, rolling, and folding.As the matrix of flexible conductive adhesives, polysiloxane has many advantages oftoughness, thermal stability and low moisture absorption. However, the low cohesive energyand wettability of nonpolar backbone—Si—O—Si—lead to its poor performance in adhesiveforce and conductivity. To solve above problems, hyperbranched poly （amine-ester）（HBP3-MA）with terminal acrylic groups was introduced. Silver nanoparticles（AgNPs）arein situ generated and sintered at low temperature in the system to improve overallperformance of polysiloxane electrically conductive adhesives（ICAs）.Curing condition combined with formula composition of polysiloxane ICAs were studiedby Differential Scanning Calorimeter（DSC）and Fourier Transform Infrared（FTIR）.Electrical conductivity, shear performance, ageing properties and flexible performance ofpolysiloxane ICAs were studied. The results showed that volume resistivity decreased withincreasing conductive fillers Ag-coated Cu flakes, while adhesive property was just theopposite. In addition, polysiloxane ICAs had a good performance in flexibility conductivity,volume resistivity rising with decreasing bending radius and prolonging of aging time.The structure of synthetic hyperbranched poly （amine-ester）（HBP3-MA） wascharacterized by Fourier Transform Infrared（FTIR）, Elemental analysis（EA）and NuclearMagnetic Resonance （NMR）. HBP3-MA modified polysiloxane ICAs had a betterperformance in shear measurement since HBP3-MA was involved in the curing reaction ofpolysiloxane bring in a mass of polar groups.AgNPs were in situ generated and simultaneously low temperature sintered in modifiedpolysiloxane ICAs by using HBP3-MA as template. The conductivity and shear strength of theHBP3-MA modified polysiloxane/nano-silver ICAs were investigated that silver precursorcould improve its conductivity and adhesion. When the content of the precursor silver acetate was4.4phr, the optimum volume resistivity and the shear strength were achieved, which were3.1×10-3Ω cm and0.47MPa, respectively. HBP3-MA modified polysiloxane/nano-silverICAs had a better performance in aging test.The structural morphology（the size and dispersion）of in-situ reduced AgNPs and theinterfacial structure of composite system were studied by Ultraviolet-visible spectrometry（UV-Vis）, X-Ray diffraction（XRD）, Transmission electron microscopy（TEM）andScanning electron microscopy（SEM）. Also, conductivity mechanism of the compositesreinforced by metal nanoparticles was discussed. At the curing temperature, silver acetatedecomposed and AgNPs were in situ generated in the polymer matrix with a25nm size. Thelow temperature sintering of AgNPs anchored on the surface of Ag-coated Cu flakes,enhanced interfacial bond of Ag-coated Cu flakes and decrease the overall contact resistance.Moreover, the sintering of AgNPs prevented the Ag-coated Cu flakes from being oxidizingand improved the reliability of HBP3-MA modified polysiloxane/nano-silver ICAs in hightemperature and humidity. |
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