High Optical Transparency and Low Dielectric Constant Polyimides Containing Trifluoromethyl and Cyclohexane Groups

A series of novel polyimides (PIs) were polymerized from 4,4'-(cyclohexane-1,4-diylbis(oxy))bis(3-(trifluoromethyl)aniline) (1) and 1,4-bis((4-amino-2-(trifluoromethyl)phenoxy)methyl)cyclohexane (2), with two aromatic tetracarboxylic dianhydrides using the typical one-step method. The inherent viscosity of these resulting PIs were in the range of 0.53-0.91 dl/g in N,N-dimethylacetamide (DMAc) at 30 degrees C. They were readily soluble in numerous solvents, such as N-methyl-2-pyrrolidone (NMP), DMAc, N,N-dimethylformamide (DMF), meta-cresol (m-Cresol), and dimethylsulfoxide (DMSO). The PI films showed high optical transparency and were colorless with an ultraviolet-visible absorption cut-off wavelength around 330 nm, and a low dielectric constants of 2.49-2.93 at 1 MHz. The PIs also showed good thermal properties. Their glass-transition temperatures (T-g) were higher than 337 degrees C, and the temperatures of 10% weight loss in air and nitrogen were higher than 412 degrees C and 417 degrees C. Furthermore, the PI films possessed good mechanical properties with tensile strengths of 54-71 MPa, elongations at break of 11.6%-17.3% and low moisture absorption (<1.34%). Due to their properties, these PIs could be considered as materials for photoelectric and micro-electronic applications.