Fabrication And Properties Of Graphene Encapsulated Styrene-butyl Acrylate Copolymer Microspheres

In recent years,with the rapid development of the electronics industry,electronic products have gradually developed in the direction of miniaturization and high energy storage.In order to make microelectronics tend to be miniaturized,it is essential for capacitor materials having a high dielectric constant,low dielectric loss,and ease of processing,and the development of dielectric materials has attracted attention.Most polymer-based materials have low dielectric constants,and research to improve their dielectric properties is an exploratory subject.From the development of ceramic fillers to conductive fillers to composite fillers,graphene is a conductive filler.Because of its high aspect ratio,it has a significant advantage in improving the dielectric properties of polymer matrices.Therefore,this paper will design the composite filler with trace reductive graphene oxide(rGO)to improve the dielectric properties of polymer matrix.In this paper,graphene/styrene-butyl acrylate composite microspheres(rGO/SBA-a,rGO/SBA-b,rGO/SBA-c)were prepared by conventional emulsion polymerization,soap-free emulsion polymerization and miniemulsion polymerization,to explore the effect of different microsphere structures on the dielectric properties of polymethyl methacrylate(PMMA)and polystyrene(PS).Specially,they were described as follows:The morphology,particle size distribution,dynamic mechanical properties and dielectric properties of graphene/styrene-butyl acrylate composite microspheres were investigated.The results show that rGO/SBA-a is a microsphere in which rGO is randomly distributed in SBA-a,rGO/SBA-b is a microsphere of rGO coated SBA-b,rGO/SBA-c is a structure in which insulating layer wraps rGO,and its particle size of the microspheres increased with the increase of rGO content.With the addition of rGO,the glass transition temperature Tg(ST)of the styrene segment of the rGO/SBA-a composite is up to 78°C.The(2 wt%)rGO/SBA-c prepared by the miniemulsion polymerization method has the highest dielectric constant up to 11356(at a frequency of 1 KHz),and is 1925 times the pure SBA-c dielectric constant(5.9).It is shown that this type of composite filler-insulating layer wraps the structure of rGO,which is more advantageous for increasing the dielectric constant of the polymer-based material.The effects of rGO/SBA-a and rGO/SBA-b composites on the cross-sectional morphology,dynamic mechanical properties and dielectric properties of graphene/polymethyl methacrylate composites were investigated.And the advantages of different preparation methods to improve the dielectric properties of PMMA composites were compared and analyzed.The results show that the storage modulus of PMMA/rGO(0.15 wt%)/SBA-a(13 wt%)composites is up to 3038 MPa(at a temperature of 40°C),PMMA/rGO(0.21 wt%)/SBA-a(7 wt%)composites have a Tg of up to 132.5?;PMMA/rGO(0.15 wt%)/SBA-b(13 wt%)composites have a storage modulus of up to 3712 MPa(at a temperature of 40?),PMMA/rGO(0.28 wt%)/SBA-b(7 wt%)composite has a Tg of up to 135.5°C.In addition,the preparation of rGO/SBA-b composite filler by soap-free emulsion polymerization is more advantageous(compared to traditional emulsion polymerization)for improving the dielectric properties of PMMA composites.The PMMA/rGO(0.26 wt%)/SBA-b(13 wt%)composite has a dielectric constant of up to 46.64(1 KHz).It is 11.08 times the dielectric constant of PMMA.The structure of rGO coated SBA-b increases the dispersion degree of rGO in PMMA matrix and enhances the polarization degree of interface.It is beneficial to form a three-dimensional network structure of rGO in PMMA matrix,and obtain a high dielectric constant and low permeability threshold PMMA/rGO/SBA-b composite.The effects of rGO/SBA-c composite filler on the cross-sectional morphology,dynamic mechanical properties and dielectric properties of graphene/polystyrene composites were investigated.The advantages of different preparation methods for improving PS composites were compared and analyzed.The results show that the addition of rGO can improve the storage modulus of PS/rGO/SBA-c composites to a certain extent.When the temperature is 40?,the storage modulus of PS/rGO(0.21 wt%)/SBA-c(7 wt%)reached 3060 MPa.The rGO/SBA-c composite filler prepared by miniemulsion polymerization is the best solution for improving the dielectric properties of PS composites.Among them,the PS/rGO(0.39 wt%)/SBA-c(13 wt%)composite has a dielectric constant of up to 10.91 and a dielectric loss of 0.41.The insulating layer AMPS encapsulates the structure of rGO.Due to the existence of the isolation layer,it can hinder the leakage current in the interface polarization and reduce its dielectric loss,thereby producing PS/rGO/SBA-c composite with high dielectric constant,low dielectric loss and low percolation threshold.