The Synthesis and Characterization of Highly Fluorinated Aromatic Polyimides

• Published in: Journal of fluorine chemistry 2019-08, Vol.224, p.100-112
• Main Authors: Simone, Christopher D., Vaccaro, Eleonora, Scola, Daniel A.
• Format: Article
• Language: English
• Subjects: Byproducts; Diamines; dielectric constant; fluorinated polyimides; Fluorination; High temperature; microwave synthesis; Moisture absorption; Polyimide resins; Synthesis; thermal stability
• ISSN: 0022-1139; 1873-3328
• DOI: 10.1016/j.jfluchem.2019.05.001

[Display omitted] •Novel Octafluoro aromatic polyimides with low dielectric constants have been synthesized.•A novel sterically hindered dianhydride, 8 FDA, 4,4’-(2,2,2-trifluoro-1-pentafluorophenylethylidene)diphthalic anhydride was synthesized.•8 FTM, bis(3,4-dimethylphenyl)pentafluorophenyltrifluoromethylmethane was also synthesized.•The steric requirements for 8 FTM synthesis caused the formation by-products resulting in low 8 FTM yields. The synthesis and characterization of pendant octafluoro aromatic polyimides (8 F-PIs) derived from 4, 4’-(2, 2, 2-trifluoro-1-pentafluorophenylethylidene)diphthalic anhydride (8 FDA) and several aromatic diamines is described. The synthesis of bis(3,4-dimethylphenyl)pentafluorophenyltrifluoromethylmethane (8 FTM), and 2-(3, 4-dimethylphenyl)-2-pentafluorophenyl-2-trifluoromethylethanol (8 F-OH), the precursors to 8 FDA are also discussed. The synthesis of 8 FTM is accompanied by two major by-products resulting in a low yield of desired product. The presence of the pentafluorophenyl group in the backbone of the fluorinated polyimides introduces flexibility and free volume manifested by lower Tg’s than more rigid analogs. The highly fluorinated polyimides exhibited lower dielectric constants than most fluorinated polyimides. The 8 F-PIs cured at a maximum temperature 371 °C/1 hr. exhibited thermal stabilities typical of high performance fluorinated polyimides. High temperature (436 °C) and pressure (281.2 kg/m2, 4000 psi.) post cure of 8 F-PI prepared from 8 FDA and p-phenylene diamine exhibited high thermo-oxidative stability, high density and low moisture absorption.