High optical transparency, low dielectric constant and light color of organosoluble fluorinated polyimides based on 10,10-bis[4-(4-amino-3-trifluoromethylphenoxy)phenyl]-9(10H)-anthrone

Reducing the Permittivity of Polyimides for Better Use in Communication Devices

Recent studies have shown that introducing fluorinated groups into polyimide (PI) molecules can effectively reduce the dielectric constant (Dk) and dielectric loss (Df) of PIs. In this paper, 2,2'-bis[4-(4-aminophenoxy) phenyl]-1,1',1',1',3,3',3'-hexafluoropropane (HFBAPP), 2,2'-bis(trifluoromethyl)-4,4'-diaminobenzene (TFMB), diaminobenzene ether (ODA), 1,2,4,5-Benzenetetracarboxylic anhydride (PMDA), 3,3',4,4'-diphenyltetracarboxylic anhydride (s-BPDA) and 3,3',4,4'-diphenylketontetracarboxylic anhydride (BTDA) were selected for mixed polymerization to find the relationship between the structure of PIs and dielectric properties. Firstly, different structures of fluorinated PIs were determined, and were put into simulation calculation to learn how structure factors such as fluorine content, the position of fluorine atom and the molecular structure of diamine monomer affect the dielectric properties. Secondly, experiments were carried out to characterize the properties of PI films. The observed change trends of performance were found to be consistent with the simulation results, and the possible basis of the interpretation of other performance was made from the molecular structure. Finally, the formulas with the best comprehensive performance were obtained respectively. Among them, the best dielectric properties were 14.3%TFMB/85.7%ODA//PMDA with dielectric constant of 2.12 and dielectric loss of 0.00698.

Synthesis of quaternary copolymerized fluorine-containing polyimides with good thermal properties and low dielectric constant

Novel fluorine-containing polyimides were synthesized through copolymerization by using 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) and 4,4′-(4,4′-isopropydenediphenox-y) bis-(phthalic anhydride) (BPADA) as dianhydrides and 4,4′-oxydianiline (ODA) and 2,2 - Bis [4-(4-aminophenoxy)phenyl]-hexafluoropropanane (HFBAPP) as diamines. Noncoplanar structure, flexible ether bond, and trifluoromethyl give the polyimide good thermoplastic, solubility, and heat resistance. The glass transition temperatures of polyimide films are 232.5°C∼262.2°C, the 5% weight loss temperatures are 521.5°C∼531.0°C, and the residual mass is more than 50% as heating to 800°C. With the increase of HFBAPP content in diamine, the dielectric constant of the material decreases from 3.21 to 2.78, and the dielectric loss decreases from 0.00962 to 0.00687 at 1 MHz, which greatly improves the dielectric properties of the material.

New fluorinated polyimides based on 1,2-bis(4-aminophenyl)-4,5-bis(4-trifluoromethylphenyl)-1H-imidazole

A new aromatic unsymmetrical diamine containing imidazolyl and trifluoromethyl groups, 1,2-bis(4-aminophenyl)-4,5-bis(4-trifluoromethylphenyl)-1H-imidazole was synthesized. A series of novel fluorinated polyimides (PIs) were prepared by polycondensation of this diamine monomer with various aromatic dianhydrides via one-step process. The resulting PIs bearing inherent viscosities of 0.45–0.61 dL/g were amorphous and readily soluble in organic polar solvents such as NMP, DMF, DMAc, THF, and CHCl3. These new PIs exhibited good thermal stability with 10% weight loss temperatures of 530–560°C and char yields of 61–65% at 800°C in nitrogen, as well as good flame retardancy with limited oxygen index value of 40.6–42.8, and outstanding hydrophobicity with the contact angle of 85.2–93.5°. Meanwhile, all the obtained PIs exhibited low water uptake of 0.30–0.53%, strong UV-vis absorption in the range of 267–310 nm in DMF solution, and their films presented high optical transparency with a cut-off wavelength in the 355–392 nm range. Except for the PI film derived from pyromellitic dianhydride, the other PI films had the tensile strength in the range of 53.2–74.1 MPa, elongation at breakage of 6–15%, and tensile modulus of 1.0–1.5 GPa, respectively.