Syntheses and properties of new aromatic polyamides based on 1,4-bis(4-aminophenoxy)naphthalene and comparison with its related isomers

New polyamides (PAs, III-A(a-h)) were synthesized by the direct polycondens ation of 1,4,-bis(4-aminophenoxy)naphthalene (I-A) with various aromatic di carboxylic acids. These polymers were obtained in quantitative yields with inherent viscosities of 0.84-1.26 dL g(-1). Except for III-A(a,e), most of the polymers were soluble in aprotic polar solvents such as N,N-dimethylace tamide (DMAc) and N-methyl-2-pyrrolidone (NMP), and could be solution cast into transparent, flexible and tough films. The glass transition temperatur es of these polyamides ranged from 250-288 degrees C. Thermogravimetric ana lyses confirmed that these polymers were fairly stable up to 430 degrees C, and 10% weight loss temperatures were recorded in the range of 493-523 deg rees C under nitrogen and 483-500 degrees C under air atmosphere. Compared to polyamides with similar structures like 1,5-bis(4-aminophenoxy)naphthale ne (series III-B) and 1,4-bis(4-aminophenoxy)benzene (series III-C) or the isomeric 1,4-bis(4-carboxylphenoxy)naphthalene (series IV), the solubility of III-A(d) was higher than III-B-d and III-C-d in DMAc and NMP, while othe r polymers III-A showed higher solubility than those of III-C in pyridine a nd m-cresol. The crystallinity of series III-A was lower than III-B, III-C, and IV. Polymers of In-A also exhibited better thermal stability than thos e of series IV.