Synthesis and characterization of colorless polyimides derived from 4-(4-aminophenoxy)-2,6-dimethylaniline

Abstract

A new aromatic polyimides (PIs) having asymmetric aromatic diamine with methyl groups at the ortho position of amino group has been developed to prepare transparent film in the visible region. The all aromatic PIs presented here are derived from 4-(4-aminophenoxy)-2,6-dimethylaniline (APDMA) and aromatic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4'-oxydiphthalic anhydride (ODPA), 4,4'-biphthalic anhydride (BPDA), and pyromellitic dianhydride (PMDA) via a two-step polycondensation. All PIs show good thermal properties: 5% weight loss at a temperature range of 510-529 A degrees C and their glass transition temperature found above 290 A degrees C. The PIs exhibit good optical transparency, such as cut-off wavelength in the region of 296-358 nm and above 92-99% at 550 nm. In addition, all PIs show low refractive indices in the range of 1.567-1.637 at wavelength of 637 nm and low birefringence.