Synthesis and Properties of New Fluorinated Polyimides Derived from an Unsymmetrical and Noncoplanar Diamine

摘要

A new unsymmetrical and noncoplanar diamine containing trifluoromethyl and trimethyl groups, 1,4-bis(4- amino-2-trifluoromethylphenoxy)-2,3,5-trimethylbenzene (2), was synthesized using 2,3,5-trimethylhydroquinone and 2-chloro-5-nitrobenzotrifluoride as starting materials. A series of fluorinated poly(ether imide)s (PEIs) (4a-4d) were prepared from diamine 2 with four aromatic dianhydrides via a one-step high-temperature polycondensation procedure. The obtained PEIs were readily soluble in most organic solvents and could be solution-cast into flexible and strong films. The resulting thin films exhibited light color and good optical transparency with a cutoff wave- length of 356--376 nm. They also displayed good thermal stability with glass transition temperatures (Tg) above 281℃, 10% weight loss temperatures in the range of 482--486 ~C, and the weight residue more than 55% at 800℃ in nitrogen. Moreover, they revealed low dielectric constants (2.77-2.93 at 1 MHz) and low moisture absorp- tions (0.41%-0.57%).