Soluble aromatic polyamides bearing asymmetrical diaryl ether groups

A series of novel aromatic polyamides containing asymmetrical diaryl ether structure were synthesized by the phosphorylation polyamidation of 5-(4-aminophenoxy)-1-naphthylamine with various dicarboxylic acids. The polymers were obtained in high yields and moderately high inherent viscosities (0.74-1.36 dl/g). Except for one example, all the polyamides were amorphous and readily soluble in many organic solvents and could afford flexible and tough films via solution casting. The cast films exhibited good mechanical properties with tensile strengths of 90-128 MPa, elongations at break of 9-64%, and initial moduli of 2.08-3.08 GPa. Glass-transition temperatures ranged from 222 to 288 °C by DSC. Thermal stabilities by TGA for the polymer series ranged from 462 to 517 °C in air at the point of 10% weight loss. These polyamides displayed a lower crystallinity and better solubility and film-forming capability than the corresponding analogues derived from symmetrical 1,5-diaminonaphthalene and 1,5-bis(4-aminophenoxy)naphthalene.