Preparation And Research Of Polyimide Aerogel And Its Hybrid Aerogel

Carbon aerogels have attracted tremendous attention due to their light weight,high porosity,large surface area,excellent electrical and thermal conductivity.However,in most cases the obtained carbon aerogels,mainly graphene aerogels are so fragile that restricts their large-scale application.Some are easily irreversibly deformation when compressed to a high strain(ε>70%)or suffered several compressive cycles.One important and efficient route to enhance the elasticity and robustness of aerogels is to construct 3-demensional polymer-based nanocomposite aerogels,which can enhance the mechanical properties,reduce the cost and extend the application fields of both nanofiller and polymer matrix.Polyimide(PI)is a kind of outstanding engineering plastic due to its excellent mechanical properties,thermal stability,chemical resistance and good dielectric properties.Inspired by this,the PI is integrated into nanocomposite to enhance the comprehensive properties of aerogels.Herein,we report a novel two-step approach to form self-assembly nanocomposite aerogels driven by the strong interactions between water-soluble polyimide(PI)precursor polyamic acid(PAA)and functionalized multi-walled carbon nanotubes(MWNTs)or sulfonated graphene.The PI therein constituted the framework of the nanocomposite and raised the strength of the cell walls,which endowed aerogels with super-elasticity and robustness.The functionalized multi-walled carbon nanotubes or sulfonated graphene was distributed uniformly into water via physical ultrasonic method followed by blending with PAA molecular.As concerned with functionalized MWNTs,during the imidization process,electrically insulating PAA/MWNTs aerogels were converted to conductive PI/MWNTs nanocomposite aerogels owning to the removal of their oxygenic functional groups of MWNTs.Moreover,adding MWNTs contributes to the reduction of shrinkage notably,which can be evidenced by SEM measurement and density data.And the thermal stability can be increased slightly by adding MWNTs-OH nanofiller,either.The nanocomposite aerogels displayed a high elastic modulus,high compressive stress,superior robustness and high stress-sensitive electrical conductivity.As for sulfonated graphene/PI nanocomposite aerogels,adding MWNTs contributes to the reduction of shrinkage notably,which can be evidenced by SEM measurement and density data.Moreover,it can further reduce the dielectric constant.The obtained nanocomposite shows tremendous potential to apply into the next generation of IC production that may require materials to have lower dielectric constants.