Synthesis And Properties Of Fluorinated Polyimides And Synthesis

Polyimides rank among the most heat-resistant polymers and are widely used in high temperature plastics,adhesives,dielectrics,photoresists,nonlinear optical materials,membrane materials for separation,and Langmuir-Blodgett(LB)films,among others.Additionally,polyimides are used in a diverse range of application,including the fields of aerospace,defense,and opto-electronics;they are also used in liquid crystal alignments,composites,electroluminescent devices,electrochromic materials,polymer electrolyte fuel cell,polymer memories,fiber optics,etc.Polyimides derived from monomers with noncoplanar(kink,spiro,and cardo structures),cyclic aliphatic,bulky,fluorinated,hetero,carbazole,perylene,chiral,non-linear optical a nd unsymmetrical structures have been described.In recent years,the study of fluorinated polyimides has become a concerning topic,fluorinated polyimides have the following characteristics:(1)thermal and thermal oxidative stability;(2)to reduce the diamine nucleophilic reaction activity;(3)low crystallinity,high permeability,low permeability and selectivity;(4)low dielectric constants and refractive index;(5)the solubility and thermal expansion coefficient increased.4.4'-terephthaloydiphthalic anhydride(TDPA)and 4,4'-isophtthaloyphthalic anhydride(IDPA)are isomers,and IDPA could regard as the isomers of Larc-I-TPI,which has been applied to high temperature adhesive,high temperature resistant composite material laminate and electrical insulating paint materials and other products.TDPA-PI's structure is more regular has not been reported in the literature,PI prepared by TDPA possess higher thermal stability and tensile strength.Fluorinated polyimides could be synthesized by diamine and fluorine dianhydride or dianhydride and fluorine diamine.Study the imfluence in structures and characristics of PI,di-ketone fluorinated polyimides were synthesized by TDPA(as the monomer of dianhydride)diamine with fluorinated three methyl(as the monomer of diamine).In addition,the preparation of novel soluble thermal plastic PI as a target,to synthesis a kind of di-ketone dianhydride precursor,and polycondenst with semi flexible aromatic diamine for preparing soluble thermoplastic polyimide,the main research contents and results are as follows:(1)High molecular weight poly(amic acid)(PAA)solution was prepared by low-temperature polycondensation between TDPA and 2,2'-bis(trifluoromethyl)-4,4'-diamino biphenyl(TFMB).TDPA/TFMB PI films and molding powder was by thermal imidization and chemical imidization process individually,the films was non crystalline,molding powder was part of crystallization;PI films have good tensile strength as 72.26 MPa and low water absorption rate;PI molding powder is soluble in common polar original solvents and have good performance in the thermal properties and thermal stability.(2)High molecular weight poly(amic acid)(PAA)solution was prepared by low temperature polycondensation of TDPA and 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane by HFBAPP.TDPA/HFBAPP PI films and moulding powder were synthesized by thermal imidization and chemical imidization,the films was non crystalline,molding powder was part of crystallization;PI films with good mechanical properties,tensile strength was 70.79 MPa,low water absorption;the PI molding powder also has good solubility,good thermal properties and thermal stability.(3)TDPA,PMDA and TFMB were prepared by the reaction of copolyimides,change two dianhydride ratio to alter proportion of rigid,improving the total required performance of polyimide.When the ratio of TDPA to PMDA was 1:1,the tensile strength of the films was 112.8MPa,and the thermal properties were improved.(4)4-di(3',4'-dimethybenzoyl)diphenyl ether,two 4,4-di(3',4'-dimethybenzoyl)biphenyl,two type aromatic compounds was prepared in the low temperature Friedel-Crafts acylation reaction and to test the structure by using of FT-IR 1H-NMR.The results indicated that the two compounds were the target products.