High Glass Transitions of New Polyamides, Polyimides, and Poly(amide−imide)s Containing a Triphenylamine Group: Synthesis and Characterization

Abstract

A new triphenylamine-containing diamine monomer, 4,4‘-diamino-3‘ ‘,4‘ ‘-dimethyltriphenylamine (DADT), was successfully synthesized by the cesium fluoride-mediated condensation of 3,4-dimethylaniline with 4-fluoronitrobenzene, followed by reduction. The monomer was reacted with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to produce a series of novel polyamides and polyimides, respectively. A new triphenylamine-containing dicarboxylic acid monomer, 4,4‘-trimellitimido-3‘ ‘,4‘ ‘-dimethyltriphenylamine (TDT), was successfully synthesized by refluxing the diamine, DADT, with trimellitic anhydride in glacial acetic anhydride. A series of new poly(amide−imide)s were prepared from TDT with various diamines by the direct polycondensation. The polymers were obtained in quantitative yields with inherent viscosities of 0.61−2.28 dL g-1. Most of the polymers dissolved in N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, pyridine, and cyclohexanone. These polymers, especially poly(amide−imide)s, showed high glass transition temperatures between 254 and 326 °C. These polymers were fairly stable up to a temperature around or above 400 °C and lost 10% weight in the range of 430−566 and 462−574 °C in nitrogen and air, respectively. These tough and flexible polymer films had a tensile strength of 82−145 MPa, an elongation at break of 5−11%, and a tensile modulus of 1.7−3.3 GPa. The UV−vis absorption spectra revealed that most of the polymers had absorption maxima around 303 nm. Cyclic voltammograms of the polyamides, polyimides, and poly(amide−imide)s showed an oxidation wave with a peak around 0.9, 1.1, and 1.3 V, respectively.