Synthesis and characterization of new soluble aromatic polyamides derived from 1,4-Bis(4-carboxyphenoxy)-2, 5-di-tert-butylbenzene

Aromatic polyamides based on a novel bis(ether-carboxylic acid) were synthesized by the direct phosphorylation condensation method. 1,4-Bis(4-carboxyphenoxy)-2,5-di-tert-butylbenzene was combined with various diamines containing flexible linkages and side substituents to render a set of eight novel aromatic polyamides. The polymers were produced with high yields and moderate to high inherent viscosities (0.49–1.32 dL/g) that corresponded to weight-average and number-average molecular weights (by gel permeation chromatography) of 31,000–80,000 and 19,000–50,000, respectively. Except for a single example, the polyamides were essentially amorphous and soluble in a variety of common solvents such as cyclohexanone, dioxane, and tetrahydrofuran. They showed glass-transition temperatures of 250–295 °C (by differential scanning calorimetry) and 10% weight loss temperatures above 460 °C, as revealed by thermogravimetric analysis in nitrogen. Polymer films, obtained by casting from N,N-dimethylacetamide solutions, exhibited good mechanical properties, with tensile strengths of 83–111 MPa and tensile moduli of 2.0–2.2 GPa.