A facile method was developed to fabricate highly electrically conductive aramid fibers. The immobilization of silver nanoparticles on the surface of polymetaphenylene isophthamide (PMIA) fibers was carried out by the functionalization of the PMIA fibers with poly(dopamine), followed by electroless silver plating. The poly(dopamine) (PDA) layer was deposited on the PMIA surface by simply dipping the PMIA substrate into an alkaline dopamine solution. The silver ions can be chemically bound to the catechol and indole functional groups in PDA. The silver ions were reduced into silver nanoparticles by using glucose as the reducing agent, resulting in a distinct silver layer on the PMIA surface. The obtained silver deposit was homogeneous and compact. The chemical composition of the modified PMIA fibers was studied by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS), and the crystalline structure of the silver-coated PMIA fibers was characterized by powder X-ray diffraction (XRD). The topography of the modified PMIA fibers was investigated by scanning electron microscopy (SEM). The four-point probe resistivity meter was used to study the electrical resistivity of the silver-coated PMIA fibers, the results indicated that the electrical resistivity could be as low as 0.61 mΩ·cm, with a controllable silver content, and a satisfactory stability by ultrasonic treatment.

A mussel-inspired functionalization method was developed to improve the dispersibility and compatibility of silver-coated silica (SiO2/Ag) microspheres in silicone rubber matrix; at the same time, the high conductivity of the microspheres was maintained. The poly­(dopamine) (PDA) layer was deposited on SiO2/Ag surface by spontaneous polymerization of dopamine. The SEM images showed that the SiO2/Ag/PDA microspheres are uniformly distributed and firmly integrated with silicone rubber. The PDA layers effectively improved the interfacial interaction between fillers and rubber matrix. The electrical resistivity of the SiO2/Ag/PDA/MVQ composites can be well controlled by adjusting the dopamine deposition time. Due to the favorable dispersibility and compatibility of the SiO2/Ag/PDA in the rubber matrix, the composites exhibited a dramatic increase in tensile strength (47%) and maintained their low electrical resistivity of 8.3 × 10–3 Ω·cm in the meanwhile at dopamine deposition time of 8 h. This approach can be extended to modify other particles to improve their compatibility in matrix.

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