Using acetone as a solvent

a dinitro compound 9

9-bis(3-nitro-4-hydroxyphenyl) fluorene was synthesized by the nitration reaction of 9

9-bis(4-hydroxyphenyl) fluorene (BHF) using concentrated nitric acid at room temperature.And then

9

9-bis(3-amino-4-hydroxyphenyl) fluorene (BAHF) was obtained via the catalytic reduction with hydrazine hydrate and Pd/C.The copoly(amic acid) containing phenolic hydroxyl was synthesized from the diamine BAHF

9

9-bis(4-aminophenyl) fluorene (BAF) and 4

4'-hexafluoroisopropylidinedi(phtalic anhydride) (6FDA) via the low-temperature solution polycondensation reaction.The thermally induced rigid membrane materials of copolyimide (CPI) and poly(imide-benzoxazole) (PI-PBO) were prepared by the thermal imidization and thermally induced rearrangement reaction.The structure

thermal properties and gas separation performance of these membrane materials were characterized by nuclear magnetic resonance (NMR)

Fourier transform infrared spectroscopy (FTIR)

X-ray diffraction (XRD)

thermogravimetric analyzer (TGA)

differential scanning calorimetry (DSC) and gas permeation performance testing means.The experimental results show that these thermally induced rigid membranes mainly exhibit amorphous structure

and the glass transition temperature (Tg) is about 340℃.It means that the CPI was a random copolymer.With the increase of thermal treatment temperature

the gas permeabilities of H2

O2

N2

CH4 and CO2 of thermally induced rigid membranes increased gradually.When the thermal treatment temperature reached 450℃

the gas permeabilities of O2

N2

H2

CH4 and CO2 of the thermally induced rigid membrane were 229.03 and 53.26

1497.35

33.52 and 818.76 Barrer separately.These thermally induced rigid membranes containing bulky fluorene and hexafluoroisopropyl groups could be expected to be used in the gas separation applications.