Study On Synthesis And Properties Of Fluorinated Copolyimide Films

Aromatic polyimides have excellent thermostability,mechanical properties and dielectric properties.It is currently one of the best packaging and filling materials in the field of microelectronics and information.Comonomers,copolymerization ratios and copolymerization methods are designed for the molecular structure and chain sequence of polyimide,so as to regulate the properties of polyimide materials.Polymerization and broadening the application fields of aromatic polymerization have become one of the most eye-catching applications.In this paper,4,4'-(hexafluoroisopropyl)-phthalic anhydride(6FDA),4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl(TFMB),3,4'-diaminodiphenyl ether(m-ODA)and 4,4'-diaminobenzoylaniline(DABA)were synthesized with N-methyl pyrrolidone(NMP)as solvent.Random copolymerization is a simple mixture of two diamines and one dianhydride,while block copolymerization is the first synthesis of amine terminated and anhydride terminated oligomers,followed by further polycondensation.A series of copolymeric fluorinated polyimides were synthesized by one-step high temperature method,the thickness is 20?30?m.The solution was precipitated into powder and dissolved in N,N'-dimethylacetamide(DMAc).Then a series of copolymeric fluorinated polyimides films were prepared by gradient heating.The prepared two series of polyimides are 6FDA-TFMB/m-ODA(?-PI)and 6FDA-DABA/m-ODA(?-PI)respectively.The molecular structure and molecular chain of the two copolymerized polyimides are prepared.Aggregate structure,heat resistance,and thermal studies have found that substituted comonomers and copolymerization ratios can change the sequence of molecular chain segments to a certain extent,affect the intermolecular forces,and change the performance of copolymerized polyimide films.The details are as follows:1.Compared with the?-PI system and the?-PI system,since the content of trifluoromethyl groups(-CF₃)in the?-PI system is reduced,the steric hindrance of polyimide molecular chain in?-PI system is small,the force between molecular chains is strong,the average molecular chain spacing is reduced,the degree of orientation of molecular chain along in-plane and out of plane is increased,and the aggregation structure of molecular chain is more regular.Therefore,?-PI with the rigidity of the linear amide diamine monomer DABA in the system is lower than that of the biphenyl-type rigid fluorine-containing diamine monomer TFMB in the?-PI system,which makes the?-PI system of the?-PI system entangle the molecular chains.Higher than the?-PI system,the elongation of the?-PI system is caused,and the tensile modulus is lower by the existence of the flexible ether bond.The diamine monomers all contain electron-rich bridging groups,which increase the intramolecular/intermolecular charge transfer complex,and there are hydrogen bonds in the?-PI system,so the glass transition temperature of the?-PI system is relatively high.2.Because the monomers of?-PI and?-PI systems have a high concentration of quaternary carbon structures,flexible bridged ether bonds and amide bonds,these structures will be broken and split first,and then the cyclic structure will be degraded.So there are two weight loss peaks in the derivative thermogravimetric curve(DTG)of these two systems.However,the?-PI system has more susceptible structures,so the thermal stability is relatively worse.Both the flexible ether bond and the amide group are hydrophilic groups,which can contain the?-PI system with more two structures,and its hydrophobic properties are poor.3.?-PI system and?-PI system compared to their respective block system and random system,block system than random system state of aggregation of molecular chain structure more neat and orderly,so block system has good heat resistance and mechanical properties.In addition,due to the molecular chain close degree increase also makes the hydrophobic properties of block system is better.4.Whether it is?-PI system polyimide or?-PI system polyimide,the increase in the content of m-ODA in the conversion system makes the aggregated structure of the molecular chains more regular and orderly,and increases the secondary bond force between the molecular chains.So the tensile strength and elongation at break continue to increase,while the heat resistance and tensile modulus decrease with the continuous increase in flexibility.The hydrophobicity also decreased with the increase of hydrophilic ether bond content.5.The factors that affect the glass transition temperature and mechanical properties of polyimide films are complex.These two properties are related to the rigidity of the macromolecular skeleton,as well as the forces within/between molecular chains and the regularity of molecular chain stacking.The external manifestation of the combined effect of many factors.