Synthesis and properties of Ortho-linked aromatic polyamides based on 4,4′-(2,3-naphthalenedioxy) dibenzoic acid

✍ Scribed by Sheng-Huei Hsiao; Kuan-Yu Chu

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 153 KB
• Volume: 35
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19971130)35:16<3385::aid-pola6>3.0.co;2-r

✦ Synopsis

A novel aromatic dicarboxylic acid monomer, 4,4-(2,3-naphthalenedioxy)dibenzoic acid ( 3), was prepared by the fluorodisplacement reaction of p-fluorobenzonitrile with 2,3-dihydroxynaphthalene in N,N-dimethylformamide (DMF) in the presence of potassium carbonate followed by alkaline hydrolysis of the intermediate dinitrile. A series of novel aromatic polyamides containing ortho-linked aromatic units in the main chain were synthesized by the direct polycondensation of diacid 3 and a variety of aromatic diamines using triphenyl phosphite and pyridine as condensing agents in the N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. The resulting polyamides had inherent viscosities higher than 0.74 and up to 2.10 dL/ g. All of these polyamides were soluble in polar solvents, such as NMP, DMF, N,Ndimethylacetamide (DMAc), and dimethyl sulfoxide. Transparent, flexible, and tough films could be cast from their DMAc or NMP solutions. The solvent-cast films had high tensile strengths and moduli. Extensions to break were relatively low, except for the polymers derived from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and 3,4-oxydianiline, which had elongations of 82 and 62%, respectively. Except for the polyamide based on p-phenylenediamine, all the other polyamides were amorphous in nature. All the polymers are thermally stable to temperatures in excess of 450ЊC in either air or nitrogen atmosphere. The polymers exhibited glass transition temperatures ranging from 183 to 260ЊC and decomposition temperatures (10% weight loss) ranging from 462-523ЊC in air and 468-530ЊC in nitrogen.