Polymer Nanocompisite Of Metal Oxide Clusters For Dielectric Application And Dynamics Study

Nanocomposites have attracted more attention due to their extensive applications and new demands of high dielectric constant materials emerge along with the development of electrical industry.However,when the content of nanoparticles reaches to a certain degree,mechanical performance of materials will degrade especially in the case of aggregation,accompanied by deterioration of dielectric properties.Therefore,it is difficult to improve the mechanical and dielectric performance of materials simultaneously.Herein polymerizable molecules were electrostatically grafted onto phosphotungstic acid molecular cluster to obtain a type of welldefined polymerizable nanoparticle that can copolymerize with a mixture of acrylic monomers to prepare a nanocomposite.Phosphotungstic acid serves as a electrostatic cross linker inside polymer matrix.Furthermore,the intrinsic negative charges of phosphotungstic acid may prevent them from aggregating because of electrostatic repulsion.In this research,two types of polymer matrix were introduced to synthesize two kinds of nanocomposites.The first type is hydrophobic matrix,whose monomer is mixture of methyl methacrylate(MMA)and n-butyl acrylate(n-BA).MMA monomers serve as the rigid section enhancing the strength of material while n-BA monomer act as the soft section to prevent the material becoming brittle.Another type of polymer hydrophilic matrix used in this research is polyethylene glycol methacrylate(PEGMA)whose molecular weight is 360.Because of the high compatibility between phosphotungstic acid and PEG,this matrix provides the opportunity to synthesis high nanoparticle loading nanocomposites.Therefor it is possible for us to tune the properties(e.g.glass transition temperature)of the material in a broad range.The resultant nanocomposite shows apparent improvement of dielectric and mechanical properties because of the incorporating of phosphotungstic acid nanoparticle.Besides,in order to better understand molecular mechanism behind mechanical property improvements and to understand the dynamic behavior of nanocomposite after the incorporating of phosphotungstic acid nanoparticle,dynamic behaviors was studied by means of Differential scanning calorimeter,Rheology and Broadband dielectric spectrum.Furthermore,the interfacial layer between nanoparticle and polymer matrix induced by the electrostatic interaction,which is thought to be an essential part to recognize the macroscopic properties of nanocomposites,was discussed as well.