Preparation Of Graphene@Polyaniline And Dielectric Properties Of Its Composites

In polymer-based dielectric materials,the morphology,conductive structure,and distribution of the dielectric filler in the polymer matrix can have an impact on the final properties of the material.In this paper,the nano-array of polyaniline was prepared on the surface by in-situ low-temperature polymerization using the two-dimensional sheet structure of graphene oxide(GO)to form graphene oxide @ polyaniline(GO@PANI)particles with graphene as the core layer and polyaniline as the shell layer..GO@PANI(or rGO@PANI)particles with different microstructures and conductive structures were obtained by changing the synthesis conditions,controlling the degree of reduction of graphene and controlling the degree of doping of polyaniline.Then we prepared GO@PANI/PVA(or rGO@PANI/PVA)composites with alternating layer structure,and studied the effects of different structures of GO@PANI(or rGO@PANI)on their dielectric properties.The main research contents of this paper are as follows:(1)Graphene oxide was prepared by Hummers method,and GO@PANI graded heterogeneous nanomaterials were prepared by in-situ low-temperature polymerization.Then we used SEM,TEM and FT-IR to explore the effects of various variables in the reaction on the morphology and chemical composition of GO@PANI.The results showed that the addition of aniline monomer and the concentration of doping acid affect the structure of polyaniline nanoarrays on the surface of graphene oxide in GO@PANI.Subsequently,using GO@PANI synthesized under optimal conditions to carry out hydrazine reduction reaction and secondary doping treatment,and found a method for preparing graphene@polyaniline(rGO@PANI)with different core and shell conductive structures.On this basis,we studied the chemical composition and electromagnetic shielding properties of rGO@PANI with a series of different morphological structures and electrical properties.The results showed that different core and shell conductive structures of rGO@PANI would exhibit different conductivity and electromagnetic shielding properties.Among them,rGO@PANI,which had good conductivity in both shell and core layers,exhibited good electromagnetic shielding performance.Its electromagnetic shielding performance is stable above 50 dB and up to 52.7 dB in the frequency range of 8.2-12.4GHz.(2)GO@PANI/PVA composite films with alternating layer structure was prepared by layer-by-layer spin coating.Then we tested the thermal stability and dielectric properties of the composite films.The results showed that the thermal stability of the layered composite films were significantly improved after the addition of GO@PANI.In addition,since the alternating layer structure constructed a conductive/insulating/conductive alternating structure,the composite films obtained a significantly higher high dielectric constant compared to pure PVA films with a lower dielectric loss.On this basis,we investigated the effects of spin coating number,different microstructures of GO@PANI and rGO@PANI and different conductive structures on the dielectric properties of the composite films.The results showed that the dielectric permittivity of the composite film increased significantly with the increase of the number of spin coatings.And with the regularity of the graded heterostructure and the conductivity of the core/shell layer of GO@PANI and rGO@PANI increased,the dielectric permittivity of the composite films also had a improvement.The prepared composite films had a dielectric permittivity up to 36.2 at 1000 Hz,which were about 6 times of pure PVA.While maintaining a high dielectric permittivity,the prepared GO@PANI/PVA composite films exhibited a relatively low dielectric loss,which remained below 0.1 substantially.This paper provided a new idea and method for preparing composite materials with high dielectric permittivity and low dielectric loss.