Preparation And Property Of Carboxyl-Polyimide And Their Chemical Grafting Modified Separation

Material plays a supporting role in the social development,especially in many areas as the aerospace,automotive industry,and electronic appliances.The history of human evolution is also the history of material.And now,the rapid development put forward higher requirements on the material performance.The current research trend is the high strength performance,functional diversification,light mass and low cost.Polyimide materias is a kind of main chain of such molecules containing imide ring polymer materials.PI has outstanding mechanical properties,such as low temperature resistance,good thermal performance,electricity performance and wear resistance,excellent comprehensive performance,which can be widely used in the dielectric,separation membrane materials,high temperature plastic and so on.In addition,polyimide in aerospace and photoelectric also has a very broad prospects.However polyimide as main chain typically contains benzene ring structure rigidity,strong interaction between molecular chain,the chain segment accumulation is dense,causing most PI melting dissolve difficulties,difficult processing molding,is impediment to its practical application.PI also has other defects,for instance,the not ideal adhesive performance,poor transparency,thin film not owing strength and toughness at the same time,etc.In order to solve the above problems,the modification of polyimide is now an important development direction to PI.Many researchers introduced flexible polyimide main chain groups,fat ring,asymmetric substituent or big side group and using the method of copolymerization,which reduces the polyimide symmetry of molecular chain and neat degrees in order to increase the dissolved in organic solvent performance.Polymer molecular structure is to determine the performance of the underlying factors,using the relationship between molecular structure and the performance of the polymer when synthetic PI.In order to obtain not only can dissolve and heat resistant performance of polyimide,choosing 4,4'-(Hexafluoroisopropylidene)dipthalicanhydride(6FDA)participate in the reaction,monomer containing CF3 groups can effectively prevent movement with the connection of C atoms,advantageous to improve the solubility.3,5-aminobenzoic acid with functional groups and 2,2'-bis(trifluoromethyl)benzidine(TFMB)both containing rigidity benzene ring structure,are used for condensation reaction.This polyimide have good solubility,which can soluble in common organic solvents in laboratory,outstanding thermal stability and mechanical properties.Polyimide is also a good dielectric material.the four polymers with aniline react with carboxyl PI response,getting PI polymer with side chain containing aniline.Dielectric tests show that the addition of aniline make the dielectric constant of PI increased.Aniline has four states,respectively,Leucoemeraldine base,Emeraldine base,Pernigraldine base,Emeraldine salt.Dielectric tests indicated that the change of the dielectric constant of ES is more obvious.2-amino fluorene monomer react with PI polymer containing carboxyl.The fluorescence spectrum test showed that the amino of fluorene made the polyimide with fluorescence properties and the fluorescence intensity will increase with the addition of the amino of fluorine.When amino of fluorine group is the same,the paper discusses the effect of POSS monomers on the fluorescence intensity.We discovered that POSS can make the fluorescence intensity increased.On the basis of the discussion,introduced aniline four polymers as side chain of PI,fluorescence intensity can be changed by controlling the oxidation process regulation.