Synthesis and properties of aromatic polyamides based on non-, methyl-, and phenyl-substituted 4,4′-bis(1,4-phenylenedioxy)dibenzoic acids

✍ Scribed by Sheng-Huei Hsiao; Chih-Fen Chang

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 643 KB
• Volume: 34
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(199606)34:8<1433::aid-pola6>3.0.co;2-0

✦ Synopsis

SYNOPSIS

4,4'-( 1,4-Phenylenedioxy)dibenzoic acid (3), 4,4'-(2,5-tolylenedioxy)dibenzoic acid ( M e -3 ) , and 4,4'-(2,5-biphenylenedioxy)dibenzoic acid ( P h -3 ) were prepared by the nucleophilic substitution reaction of p -fluorobenzonitrile with hydroquinone, methylhydroquinone, and phenylhydroquinone, respectively, followed by alkaline hydrolysis. Several aromatic polyamides having inherent viscosities of 0.66-1.34 dL/g were directly prepared by a Yamazaki phosphorylation polyamidation technique from dicarboxylic acids 3 , Me-3, and Ph-3, respectively, with aromatic diamines using triphenyl phosphite and pyridine as condensing agents. The solubility of methyl-or phenyl-substituted polyamides was remarkably enhanced when compared to that of nonsubstituted analogues. Most of the substituted polyamides revealed an amorphous nature and were readily soluble in a variety of organic solvents including N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, dimethyl sulfoxide, and rn-cresol. Transparent, flexible, and tough films of these polymers could be cast from the DMAc or NMP solutions. These films had tensile strength of 60-100 MPa, elongation to break of 6-11%, and tensile modulus of 1.68-2.25 GPa. The glass transition temperatures (T,) of most polyamides could be determined by differential scanning calorimetry (DSC) and were in the range of 200-232°C. Thermogravimetric analyses established that these polymers were fairly stable up to 45OoC, and the 10% weight loss temperatures were recorded in the range of 458-535OC in nitrogen and 468-528°C in air atmosphere. In general, the phenyl-substituted polyamides exhibited relatively higher Tgr thermal stability, and solubility. 0 1996