New Soluble Polyimides with High Optical Transparency and Light Color Containing Pendant Trifluoromethyl and Methyl Groups

A new aromatic diamine containing trifluoromethyl and methyl groups, namely a,a-bis（4-amino-3-methylphetayl）-4-（trifluoromethyl）phenylmethane （1）, was synthesized from 2-methylaniline and 4-（trifluoromethyl）- benzaldehyde. A series of fluorinated polyimides （PIs） were prepared from the diamine with four commercially available aromatic tetracarboxylic dianhydrides using a one-step high-temperature polycondensation procedure. These obtained PIs showed excellent solubility, with the dissolvability at a concentration of 10 wt% in most solvents, and they could afford flexible and strong films. Thin films of these PIs exhibited high optical transparency and light color, with the cutoff wavelength at 324-357 nm and transmittance higher than 74% at 450 nm. Moreover, these Pls possessed eminent thermal stability and good mechanical properties.