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

Abstract

A new aromatic diamine bearing ether, trifluoromethyl and anthrone groups, 10,10-bis[4-(4-amino-3-trifluoromethylphenoxy)phenyl]-9(10H)-anthrone (BATFPA) was prepared in three steps from anthrone. BATFPA was reacted with six conventional aromatic dianhydrides in N,N-dimethylacetamide (DMAc) to form the corresponding cardo fluorinated polyimides (PIs) via the poly(amic acid) (PAA) precursors with inherent viscosities ranging from 0.82 to 1.18 dL/g and thermal imidization. All the PAAs could be cast from DMAc solution and thermally converted into transparent, flexible and tough PI films with tensile strength of 63.5–101.7 MPa, tensile modulus of 1.94–2.85 GPa and elongation at break of 3.7–13.6%. The resulting PIs were predominantly amorphous and exhibited good solubility in dipolar solvents such as DMAc, N,N-dimethylformamide and N-methyl-2-pyrrolidinone at room temperature. In particular, the PI derived from 4,4′-hexafluoroisopropylidenediphthalic anhydride was even soluble in tetrahydrofuran. These new PIs displayed excellent thermal stability with Tg of 259–329 °C, 5% weight loss temperature (Td5) of 516–530 °C and the residue of 57–64% at 800 °C in nitrogen. Meanwhile, these PIs also had low moisture absorptions (0.36–0.83%), low dielectric constants (2.35–2.96 at 1 MHz), good optical transparency with cutoff wavelengths of ultraviolet–visible absorption at 336–408 nm and more than 80% transmittance at 600 nm.