To overcom the shortcoming of fluorinated polyimide filmssuch as low reaction activity and high coefficien of thermal expansiont

rigidmonomer pyromellitic dianhydride(PMDA) were used to copolymerize with twoFluorinated monomers 4

4(hexafluoroisopropylidene)diphthalic anhydride(6FDA)and 2

2bis(trifluoromethyl) benzidine(TFMB) to form a serials of PAA solution

as control

PI-4 were synthesized by PMDA and ODA (4

4 two amino two phenylether). After that

the obtained PAA solution was heated at the following orderto produce transparent polyimide films

80℃/1h

110℃/2h

150℃/2h

200℃/1h

250℃/30min

300℃/30min

the obtained PI films which hadpyromellitic dianhydride content of 0%

20% and 40% were numbered asPI-1

PI-2

PI-3

relatively

and its phsical and chemical properties werecharacterized. The thermogravimetric analysis showed that thermal stability offluorinated films is slightly lower than that of traditional film; thedielectric tests showed that the fluoride film’s dielectric constants weresmaller than traditional polyimide film

the dielectric constant of PI-1 isless than PI-2 and PI-3 copolymer films; the UVVis spectra showed that thetransmittance of fluorinated polyimide film was significantly higher than thatof conventional film

cutoff wavelength and yellow index of PI-1

PI-2

PI-3was 355 nm

360 nm

372 nm

and 6.4

6.9

8.94

relatively.All three films’transmittance at the wavelength of 500nm were more than 90%; the tensile testshowed that the tensile strength of fluorinated polyimide films was much lowerthan that of the conventional polyimide

but it increased after the addition ofrigid monomers; the thermal expansion coefficients of four kinds of films were14.8×10-5 /℃

9.9×10-5 /℃

5.4×10-5 /℃and 4.0×10-5/℃

respectively

which were decreased with the increase of the content of of PMDA content.