Synthesis and properties of highly organosoluble aromatic polyimides containing N-(4-(di(1H-indole-3-yl)methyl)phenyl) moieties

Abstract

A new diamine monomer containing indole unit, 3,5-diamino- N-(4-(di(1H-indol-3-yl)methyl)phenyl)benzamide, was successfully synthesized and applied in the preparation of a series of polyimides (PIs) via a conventional two-step polymerization procedure with three aromatic tetracarboxylic dianhydrides. The prepared polymers showed excellent solubility in organic solvents such as N-methyl-2-pyrrolidinone (NMP), N, N-dimethylacetamide, and N, N-dimethylformamide. Flexible and strong films of PIs were obtained via casting from their solutions. The glass transition temperature of these polymers was in the range of 223–264°C. They were fairly stable up to a temperature around 300°C and lost 10% weight at 372°C in nitrogen atmosphere. All of the polymers revealed absorption maxima around 323 nm with a fluorescence emission maxima around 378–406 nm in NMP. The cyclic voltammetry of the PIs exhibited an oxidation wave with a peak at 1.07 V. The resulting polymer films had tensile strengths from 83 MPa to 107 MPa, elongates at break of 7–10%, and tensile moduli of 2.2–2.3 GPa.