Preparation And Properties Of Polyimide Composites With High Dielectric Permittivity

With its excellent thermal properties,outstanding mechanical properties,dielectric properties polyimide is widely applied in the field of microelectronics.With the progress of the era and technological innovation,electronic devices gradually towards miniaturization,integration and high-speed development,and thus put forward higher requirements for the performance of dielectric materials.Polyimide as a dielectric material,its own dielectric properties gradually cannot meet the requirements of the development,so the research of polyimide composites has been widely concerned.Different categories of polyimide composites have their own advantages and disadvantages,around the filler particles are difficult to disperse,high dielectric loss and other problems,this paper has done the following related work.Polyamido acid/fluorinated graphene（PAA/FG）composite membranes were prepared using polyamido acid（PAA）synthesized by 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride（BPDA）and 4,4’-diaminodiphenyl ether（ODA）as substrates and fluorinated graphene as fillers.Polyethylene glycol（PEG-400）was used to reduce fluorinated graphene（FG）to graphene（r FG）in high temperature,and polyimide/graphene（PI/r FG）composite films was obtained after imidization.The phase,chemical structure,dielectric properties,mechanical properties,and thermal properties of PI/r FG composite films were characterized by scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）,fourier infrared spectroscopy（FT-IR）,thermal weight loss analyzer（TG）,dynamic thermo-mechanical analyzer（DMA）,and LCR precision digital bridge.On the condition that the mechanical properties are not lost and the dielectric loss is maintained at a low level,the PI/r FG composite films has 68 times higher dielectric permittivity（ε=232.74）and 9 times higher energy storage density（W=5.614 J/cm³）compared with the pure PI.Carbon quantum dots（CQDs）synthesized by citric acid（C₆H₈O₇）and urea（CON₂H₄）were used as fillers,and PAA synthesized by BPDA and ODA as monomers were used as substrates to prepare polyamido acid/carbon quantum dots（PAA/CQDs）composite films.The polyimide/carbon quantum dots（PI/CQDs）composite films were obtained after imidation.The phase,chemical structure,dielectric properties,mechanical properties and thermal properties of PI/CQDs composite films were characterized by scanning electron microscopy（SEM）,fourier infrared spectroscopy（FT-IR）,thermal weight loss analyzer（TG）,dynamic thermo-mechanical analyzer（DMA）,and LCR precision digital bridge.Experimentally,the dielectric permittivity of pure PI is 3.4 and the dielectric loss is 0.0057 when the frequency is100 Hz.When the content of CQDs is 10%,the dielectric permittivity of PI/CQDs composite films reach the maximum value of 4.6,which is 35%higher than that of pure PI films.At 4%of CQDs,the dielectric loss reaches a minimum of 0.0018,which is 68%lower than that of pure PI films.