Colorless and high organosoluble polyimides from 2,5-bis(3,4-dicarboxyphenoxy)-t-butylbenzene dianhydride and aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

摘要

A series of polyimides III_(a-h)characterized by colorlessness,high transparency,high solubility,and good mechanical property,was synthesized from the aromatic dianhydride,2,5-bis(3,4-dicarboxyphenoxy)-t-butylbenzene dianhydride(I),and various aromatic diamines(H_(a-h))with pendent trifluoromethyl group via polyaddition,chemical imidization,and direct cast films.The III series showed more colorless than the polyimides(V and VI series)of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA)contained,the VI series was synthesized from the II with 6FDA.These films III had cut-off wavelengths between 371 and 376 nm,as well as b* value(a yellowness index)ranging from 3.0 to 4.7.In fact,it is so far the most colorless aromatic polyimide in our systematical researches.The III series had inherent viscosity ranging from 0.72 to 1.33 dL/g and showed excellent solubility in a variety of organic solvents.They were soluble in a concentration of 5-10% in the amide polar solvent,ether solvent,and chlorinated solvent.These films showed strength tensile of 97-123 MPa,dielectric constants of 2.78-3.28(1 MHz),and moisture absorptions of 0.11-0.36 wt%.The glass transition temperature of the III series was recorded at 214-259 deg C,the 10% weight loss temperature was over 468 deg C,and the residue was more than 47% at 800 deg C in nitrogen.